MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Acta Biomaterialia' source. Wed, 02 Mar 2011 15:11:41 +0100 http://www.actabiomat.org/article/PIIS1742706110004824/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118524 Sat, 30 Oct 2010 04:06:44 +0100 4118524 http://www.actabiomat.org/article/PIIS1742706110004381/abstract?rss=yes Abstract: TiO2 nanotube layers can provide greatly enhanced kinetics for hydroxyapatite formation from simulated body fluid compared with smooth, compact TiO2 surfaces. In the present work we show how this contrast in reactivity can be used to create highly defined lateral microstructures where bone-like hydroxyapatite can be deposited with very high selectivity. For this we used a photolithographic approach to produce micropatterned TiO2 nanotube layers surrounded by compact oxide that were then immersed in a simulated body fluid (SBF) solution. Not only the tubular vs. flat geometry but also the finding that compact oxides created in phosphate electrolytes in particular suppress apatite deposition are crucial for a very high reactivity contrast. Overall the results show the feasibility o... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118565 Tue, 28 Sep 2010 23:00:00 +0100 4118565 http://www.actabiomat.org/article/PIIS1742706110004113/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980678 Sat, 18 Sep 2010 10:40:07 +0100 3980678 http://www.actabiomat.org/article/PIIS1742706110004071/abstract?rss=yes Abstract: A conducting polymer-based smart coating for magnesium (Mg) implants that can both improve the corrosion resistance of Mg and release a drug in a controllable way is reported. As the ionic liquid is a highly conductive and stable solvent with a very wide electrochemical window, the conducting polymer coatings can be directly electrodeposited on the active metal Mg in ionic liquid under mild conditions, and Mg is highly stable during the electrodeposition. The electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT) coatings on Mg are uniform and can significantly improve the corrosion resistance of Mg. In addition, the PEDOT coatings can load the anti-inflammatory drug dexamethasone during the electrodeposition, which can be subsequently released upon electric stimulation. (Sour... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118567 Thu, 09 Sep 2010 23:00:00 +0100 4118567 http://www.actabiomat.org/article/PIIS1742706110004034/abstract?rss=yes Abstract: A textile polyester vascular graft was modified with methyl-β-cyclodextrin (MeβCD) to obtain a new implant capable of releasing antibiotics directly in situ at the site of operation over a prolonged period and thereby prevent post-operative infections. We investigated the influence of the curing parameters (time and temperature) that allow control of the degree of functionalization (DF) of the support by MeβCD. The inclusion of ciprofloxacin (CFX) in the MeβCD cavity was observed in solution by two-dimensional 1H NMR spectroscopy. The amount of CFX loaded on the modified graft increased with DF. Depending on the release medium (water, phosphate-buffered saline, or human plasma) and the DF of the prostheses, different kinetic profiles of release of CFX were obtained. The susta... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118553 Thu, 09 Sep 2010 23:00:00 +0100 4118553 http://www.actabiomat.org/article/PIIS1742706110004058/abstract?rss=yes Abstract: Polymeric endoaortic paving (PEAP) is a process by which a polymer is endovascularly delivered and thermoformed to coat or “pave” the lumen of the aorta. This method may offer an improvement to conventional endoaortic therapy in allowing conformal graft application with reduced risk of endoleak and customization to complex patient geometries. Polycaprolactone (PCL)/polyurethane (PU) blends of various blend ratios were assessed as a potential material for PEAP by characterizing their mechanical, thermoforming and degradation properties. Biaxial tension testing revealed that the blends’ stiffness is similar to that of aortic tissue, is higher for blends with more PCL content, and may be affected by thermoforming and degradation. Tubes of blends were able to maintain a higher ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118551 Thu, 09 Sep 2010 23:00:00 +0100 4118551 http://www.actabiomat.org/article/PIIS1742706110003909/abstract?rss=yes Abstract: Previous research on the feasibility of using biodegradable magnesium alloys for bone implant applications mainly focused on biocompatibility and corrosion resistance. However, successful clinical employment of endosseous implants is largely dependent on biological fixation and anchorage in host bone to withstand functional loading. In the present study, we therefore aimed to investigate whether bone–implant interface strength and osseointegration of a novel biodegradable magnesium alloy (Mg–Y–Nd–HRE, based on WE43) is comparable to that of a titanium control (Ti–6Al–7Nb) currently in clinical use. Biomechanical push-out testing, microfocus computed tomography and scanning electron microscopy were performed in 72 Sprague–Dawley rats 4, 12 and 24weeks after implantat... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118566 Tue, 31 Aug 2010 23:00:00 +0100 4118566 http://www.actabiomat.org/article/PIIS1742706110003958/abstract?rss=yes Abstract: Scaffolds of 13-93 bioactive glass (composition 6.0 Na2O, 7.9 K2O, 7.7 MgO, 22.1 CaO, 1.7 P2O5, 54.6 SiO2 (mol.%)) containing oriented pores of controllable diameter were prepared by unidirectional freezing of camphene-based suspensions (10vol.% particles) on a cold substrate (−196°C or 3°C). By varying the annealing time (0–72h) to coarsen the camphene phase, constructs with the same porosity (86±1%) but with controllable pore diameters (15–160μm) were obtained after sublimation of the camphene. The pore diameters had a self-similar distribution that could be fitted by a diffusion-controlled coalescence model. Sintering (1h at 690°C) was accompanied by a decrease in porosity and pore diameter, the magnitude of which depended on the pore size of the green constructs, g... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118563 Tue, 31 Aug 2010 23:00:00 +0100 4118563 http://www.actabiomat.org/article/PIIS174270611000396X/abstract?rss=yes Abstract: It is known that adsorbed adhesive proteins on implanted biomaterials modulate inflammatory responses; however, modulation of dendritic cell (DC) responses upon interaction with adhesive proteins has only begun to be characterized. DCs are specialized antigen-presenting cells that modulate both innate and adaptive immune responses. Previously we have shown that the activation and stimulatory capacity of DCs derived from C57BL6/j mice is differentially modulated by adhesive substrates. Here we extend our investigation of adhesive substrate modulation of DC responses to consider the case where the DCs had maturational defects associated with diabetes. Understanding the adhesive responses of DCs in diabetics is potentially important for immunotherapy and tissue engineering applicati... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118541 Tue, 31 Aug 2010 23:00:00 +0100 4118541 http://www.actabiomat.org/article/PIIS1742706110003879/abstract?rss=yes Abstract: Recently, the ligament–bone (LTB) junction has been emphasized for the effective transmission of mechanical force and the reduction in stress concentration between the soft ligament and hard bone tissue. The aim of this study was to regenerate an integrated LTB interface by inoculating LTB-relevant cells, isolated from fibrocartilage (FC) or ligament (LIG), separately into each designated region in a single porous cylindrical PLCL scaffold. An injectable, heparin-based hydrogel that has proved to be effective in the culture of chondrocytes as well as the sustained release of growth factor was employed to locally deliver fibrochondrocytes and osteoinductive bone morphogenetic protein-2 (BMP-2) into the FC region, to promote FC regeneration. In in vitro experiments the hydrogel-c... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118547 Sun, 29 Aug 2010 23:00:00 +0100 4118547 http://www.actabiomat.org/article/PIIS1742706110003892/abstract?rss=yes Abstract: A periodontal membrane with a graded structure allows tailoring of the layer properties to design a material system that will retain its physical, chemical and mechanical characteristics for a period long enough to optimize periodontal regeneration. In this work a novel functionally graded membrane (FGM) was designed and fabricated via sequential multilayer electrospinning. The FGM consists of a core layer (CL) and two functional surface layers (SLs) interfacing with bone (nano-hydroxyapatite, n-HAp) and epithelial (metronidazole, MET) tissues. The CL comprises a neat poly(dl-lactide-co-ε-caprolactone) (PLCL) layer surrounded by two composite layers composed of a protein/polymer ternary blend (PLCL:PLA:GEL). Electrospinning parameters involved in fabrication of the individual la... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118544 Sun, 29 Aug 2010 23:00:00 +0100 4118544 http://www.actabiomat.org/article/PIIS1742706110003880/abstract?rss=yes Abstract: The field of tissue engineering is severely limited by a lack of microvascularization in tissue engineered constructs. Biomimetic poly(ethylene glycol) hydrogels containing covalently immobilized platelet-derived growth factor BB (PDGF-BB) were developed to promote angiogenesis. Poly(ethylene glycol) hydrogels resist protein absorption and subsequent non-specific cell adhesion, thus providing a “blank slate”, which can be modified through the incorporation of cell adhesive ligands and growth factors. PDGF-BB is a key angiogenic protein able to support neovessel stabilization by inducing functional anastomoses and recruiting pericytes. Due to the widespread effects of PDGF in the body and a half-life of only 30min in circulating blood, immobilization of PDGF-BB may be necessar... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118536 Sun, 29 Aug 2010 23:00:00 +0100 4118536 http://www.actabiomat.org/article/PIIS1742706110003235/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911514 Sat, 28 Aug 2010 09:45:05 +0100 3911514 http://www.actabiomat.org/article/PIIS1742706110003727/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911513 Sat, 28 Aug 2010 09:45:05 +0100 3911513 http://www.actabiomat.org/article/PIIS174270611000382X/abstract?rss=yes Abstract: In this work we have developed a strategy for cultivating dermal papilla (DP) cells to form multiple arrayed spheroidal microtissues for transplantation on a micropatterned polydimethylsiloxane (PDMS)-based tissue culture polystyrene (TCPS) plate system. We also describe the behavior of dermal papilla cells on this platform and the spontaneous formation of spheroidal microtissues by DP cells. We used a hydrophobic PDMS arrayed chip as a master to separate the seeded cells in the TCPS culture plate. By controlling the cell seeding densities, a microwell with arrayed DP spheroidal microtissues was easily formed. Formation of DP microtissues was associated with overlapping multilayered cells on the microwells and low cell–substrate adhesivity on the PDMS film. The microwell enviro... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118554 Sun, 22 Aug 2010 23:00:00 +0100 4118554 http://www.actabiomat.org/article/PIIS1742706110003855/abstract?rss=yes Abstract: Electrospun poly(lactic acid) (PLLA) nanofibers (NF) were modified with cationized gelatin (CG) to improve their compatibility with chondrocytes and to show in vitro and in vivo the potential applications of CG-grafted PLLA nanofibrous membranes (CG-PLLA NFM) as a cartilage tissue engineering scaffold. PLLA NF were first treated with oxygen plasma to introduce –COOH groups on the surface, followed by covalent grafting of CG molecules onto the fiber surface, using water-soluble carbodiimide as the coupling agent. The effects of CG grafting and properties of NFM were characterized by scanning electron microscopy (SEM), transmission electron microscopy, thermogravimetric analysis, atomic force microscope, X-ray photoelectron spectra and Fourier transform infrared spectroscopy. In ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118546 Sun, 22 Aug 2010 23:00:00 +0100 4118546 http://www.actabiomat.org/article/PIIS1742706110003831/abstract?rss=yes Abstract: Current cardiovascular therapies are limited by the loss of endothelium, restenosis and thrombosis. The goal of this study was to develop a biomimetic hybrid nanomatrix that combined the unique properties of electrospun polycaprolactone (ePCL) nanofibers with self-assembled peptide amphiphiles (PAs). ePCL nanofibers have interconnected nanoporous structures, but are hampered by a lack of surface bioactivity to control cellular behavior. It has been hypothesized that PAs could self-assemble onto the surface of ePCL nanofibers and endow them with the characteristic properties of native endothelium. The PAs, which comprised hydrophobic alkyl tails attached to functional hydrophilic peptide sequences, contained enzyme-mediated degradable sites coupled to either endothelial cell-adhes... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118545 Sun, 22 Aug 2010 23:00:00 +0100 4118545 http://www.actabiomat.org/article/PIIS1742706110003843/abstract?rss=yes Abstract: A degradable, polar, hydrophobic, ionic polyurethane (D-PHI), with physical properties comparable to those of peripheral arterial vascular tissue, was evaluated for monocyte interactions with two different physical forms: two-dimensional films and three-dimensional porous scaffolds. Monocytes, isolated from human whole blood, were seeded onto D-PHI films and scaffolds, and differentiated to monocyte-derived macrophages (MDM) for up to 28days. The effect of surface structure on the MDM phenotype was assessed by assaying: cell attachment (DNA), activation (intracellular protein expression, esterase and acid phosphatase (AP) activity) as well as pro- and anti-inflammatory cytokines (TNF-α and IL-10, respectively). The cells on scaffolds exhibited an initial peak in total protein sy... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118534 Sun, 22 Aug 2010 23:00:00 +0100 4118534 http://www.actabiomat.org/article/PIIS174270611000379X/abstract?rss=yes Abstract: Antibacterial surface modification of biomedical materials has evolved as a potentially effective method for preventing bacterial proliferation on the surfaces of devices. However, thin antibacterial coatings or modified layers can be easily worn down when interacting with other surfaces in relative motion, thus leading to a low durability of the antibacterial surface. To this end, novel biomaterial surfaces with antibacterial Ag agents and a wear-resistant S-phase have been generated on stainless steel by duplex plasma silvering–nitriding techniques for application to load-bearing medical devices. The chemical composition, microstructure, surface topography, roughness and wettability of SS surfaces were characterised using glow discharge optical emission spectroscopy, energy-d... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118568 Thu, 19 Aug 2010 23:00:00 +0100 4118568 http://www.actabiomat.org/article/PIIS1742706110003806/abstract?rss=yes The objective of the present study is to prepare and characterize nutlin-3a loaded poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs), surface functionalized with epithelial cell adhesion molecule (EpCAM) antibody, with an aim to deliver encapsulated drug in a targeted manner to its site of action and to enhance its therapeutic efficacy many times over. The enhanced cellular uptake of EpCAM antibody conjugated nutlin-3a loaded NPs (EpCAM-nutlin-3a-NPs) over native nulin-3a, nutlin-3a loaded NPs (nutlin-3a-NPs) in HCT116 and A549 cells substantiate the targeting potentiality of conjugated system. IC50 values depicted superior antiproliferative activity of EpCAM-nutlin-3a-NPs over nutlin-3a-NPs and native nutlin-3a in the above studied cell lines. Cell cycle arrest, loss of mitochondrial ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118558 Thu, 19 Aug 2010 23:00:00 +0100 4118558 http://www.actabiomat.org/article/PIIS174270611000365X/abstract?rss=yes We describe the structural and functional properties of three-dimensional (3D) nerve guides fabricated from poly-ε-caprolactone (PCL) using the air gap electrospinning process. This process makes it possible to deposit nano-to-micron diameter fibers into linear bundles that are aligned in parallel with the long axis of a cylindrical construct. By varying starting electrospinning conditions it is possible to modulate scaffold material properties and void space volume. The architecture of these constructs provides thousands of potential channels to direct axon growth. In cell culture functional assays, scaffolds composed of individual PCL fibers ranging from 400 to 1500nm supported the penetration and growth of axons from rat dorsal root ganglion. To test the efficacy of our guide design we... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118543 Thu, 19 Aug 2010 23:00:00 +0100 4118543 http://www.actabiomat.org/article/PIIS1742706110003636/abstract?rss=yes Abstract: Bulk metallic glasses (BMGs) demonstrate attractive properties for potential biomedical applications, owing to their amorphous structure. The present work has investigated the biocompatibility of Zr-based BMGs by studying the cellular behavior of bone-forming mouse MC3T3-E1 pre-osteoblast cells. A Ti–6Al–4V alloy was used as a reference material. Pre-immersion treatment was performed on BMG samples in phosphate-buffered saline prior to cell experiments. The effects of 1at.% yttrium alloying and surface roughness on cellular behavior were examined. The general biosafety of Zr-based BMGs for MC3T3-E1 cells was revealed as normal cell responses. Pre-immersion treatment was found to effectively reduce the surface concentrations of alloying elements. Micro-alloying with 1at.% yttr... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118562 Sun, 15 Aug 2010 23:00:00 +0100 4118562 http://www.actabiomat.org/article/PIIS1742706110003648/abstract?rss=yes In this study the uptake of Ag-NP into hMSC has been analyzed and the intracellular distribution of Ag-NP after exposure determined. Non-agglomerated (dispersed) Ag-NP from the cell culture medium were detected as agglomerates of nanoparticles within the hMSC by combined focused ion beam/scanning electron microscopy. The silver agglomerates were typically located in the perinuclear region, as determined by light microscopy. Specific staining of cellular structures (endo-lysosomes, nuclei, Golgi complex and endoplasmatic reticulum) using fluorescent probes showed that the silver nanoparticles occurred mainly within endo-lysosomal structures, not in the cell nucleus, endoplasmic reticulum or Golgi complex. Quantitative determination of the uptake of Ag-NP by flow cytometry (scattergram analy... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118557 Sun, 15 Aug 2010 23:00:00 +0100 4118557 http://www.actabiomat.org/article/PIIS1742706110003661/abstract?rss=yes Abstract: Biological scaffolds used in tissue engineering are incorporated in vivo by a process of cellular in-growth, followed by host-mediated degradation and replacement of these scaffolds, in which phagocytic cells from the monocyte/macrophage cell lineage play a key role. The chemical degradation of scaffolds with collagenases is well established, but to date this has not been correlated with an in vitro model of cell mediated scaffold degradation. RAW264.7, a murine monocyte/macrophage cell line, was cultured on collagen scaffolds crosslinked either by dehydrothermal treatment (DHT) or by carbodiimide (EDC). These cells attached to collagen scaffolds, proliferated and exhibited macrophage aggregation to form giant cells. Crosslinking the scaffolds by either DHT or EDC increased the r... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118550 Sun, 15 Aug 2010 23:00:00 +0100 4118550 http://www.actabiomat.org/article/PIIS1742706110003685/abstract?rss=yes Abstract: Stem cells transit along a variety of lineage-specific routes towards differentiated phenotypes. These fate decisions are dependent not just on the soluble chemical cues that are encountered or enforced in vivo and in vitro, but also on physical cues from the cellular microenvironment. These physical cues can consist of both nano- and micro-scale topographical features, as well as mechanical inputs provided passively (from the base properties of the materials to which they adhere) or actively (from extrinsic applied mechanical deformations). A suitable tool to investigate the coordination of these cues lies in nanofibrous scaffolds, which can both dictate cellular and cytoskeletal orientation and facilitate mechanical perturbation of seeded cells. Here, we demonstrate a coordinat... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118528 Sun, 15 Aug 2010 23:00:00 +0100 4118528 http://www.actabiomat.org/article/PIIS1742706110003624/abstract?rss=yes Abstract: Cell adhesion and subsequent viability are critical initial steps in biomaterial–tissue integration and are strongly dependent on the material properties and the presence of matrix proteins. In the present study MC3T3-E1 osteoblast-like cell behavior on silicon oxide (SO) and poly(l-lactic acid) (PLLA) substrates has been examined, with a focus on the influence of the adhesive protein fibronectin and the non-adhesive protein albumin adsorbed on the substrates. Quartz crystal microgravimetry showed adsorption of fibronectin and albumin to be nearly identical on SO and PLLA. Subsequent exposure a previously adsorbed fibronectin layer to albumin decreased the rigidity of the adsorbed layer without any measurable increase in adsorbed mass. Cell adhesion and spreading were significa... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118561 Sun, 08 Aug 2010 23:00:00 +0100 4118561 http://www.actabiomat.org/article/PIIS1742706110003600/abstract?rss=yes The objective of this study was to calculate stresses produced by polymerization contraction in regions surrounding a dental resin composite restoration. Initial cracks were made with a Vickers indenter at various distances from the edge of a cylindrical hole in a soda-lime glass disk. Indentation crack lengths were measured parallel to tangents to the hole edge. Resin composites (three brands) were placed in the hole and polymerized (two light irradiation protocols) at equal radiation exposures. The crack lengths were re-measured at 2 and 10min after irradiation. Radial tensile stresses due to polymerization contraction at the location of the cracks (σcrack) were calculated from the incremental crack lengths and the fracture toughness Kc of the glass. Contraction stresses at the composit... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118564 Wed, 04 Aug 2010 23:00:00 +0100 4118564 http://www.actabiomat.org/article/PIIS1742706110003612/abstract?rss=yes This study demonstrates the importance of hierarchical and deliberate organization of the nanocomponents to optimize the mechanical properties, as is often found in nature. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118542 Wed, 04 Aug 2010 23:00:00 +0100 4118542 http://www.actabiomat.org/article/PIIS1742706110003594/abstract?rss=yes Abstract: The insufficient availability of donor organs for orthotopic liver transplantation worldwide has urgently increased the requirement for new therapies for acute and chronic liver disease. The creation of an unlimited source of donor cells for hepatocyte transplantation therapy and pharmaceutical applications may be the isolation and expansion of liver progenitor cells or stem cells. Here we report the expansion and functional differentiation of rat embryonic liver cells on biodegradable and synthetic polymeric membranes in comparison with traditional substrates, such as collagen and polystyrene culture dishes. Membranes prepared from chitosan and modified polyetheretherketone were used for the culture of liver progenitor cells derived from rat embryonic liver. Cells proliferated, ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118540 Wed, 04 Aug 2010 23:00:00 +0100 4118540 http://www.actabiomat.org/article/PIIS1742706110003569/abstract?rss=yes Abstract: Immobilization of phosphoproteins on a collagen matrix is important for the induction of intrafibrillar apatite mineralization. Unlike phosphate esters, polyphosphonic acid has no reactive sites for covalent binding to collagen amine groups. Binding of poly(vinyl phosphonic acid) (PVPA), a biomimetic templating analog of matrix phosphoproteins, to collagen was found to be electrostatic in nature. Thus, an alternative retention mechanism was designed for immobilization of PVPA on collagen by cross-linking the latter with carbodiimide (EDC). This mechanism is based on the principle of size exclusion entrapment of PVPA molecules within the internal water compartments of collagen. By cross-linking collagen with EDC, a zero length cross-linking agent, the sieving property of collagen ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118549 Tue, 03 Aug 2010 23:00:00 +0100 4118549 http://www.actabiomat.org/article/PIIS1742706110003582/abstract?rss=yes Abstract: Although physically cross-linked poly(vinyl alcohol) (PVA) hydrogels have tunable mechanical properties to match that of soft tissues, such as vascular tissue, their hydrophilic nature is not conducive to cell adhesion and spreading. For applications such as small diameter vascular grafts for coronary bypass both mechanical matching and hemocompatibility are important. Poly(amic acid) (PAA), derived from ethylene diamine tetraacetic dianhydride, is a cell-compatible polymer. It was grafted/cross-linked onto physically cross-linked PVA to provide cell compatibility. Functionalization was achieved via a one-step esterification reaction using 1,3-dicyclohexylcarbodiimide as the coupling agent and 4-dimethylaminopyridine as the catalyst. The success of the grafting reaction was verif... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118548 Tue, 03 Aug 2010 23:00:00 +0100 4118548 http://www.actabiomat.org/article/PIIS1742706110003545/abstract?rss=yes Abstract: Cardiac tissue engineering aims to regenerate damaged myocardial tissues by applying heart patches created in vitro. The present study was undertaken to explore the possible role of matrix-attached RGD peptide in the engineering of cardiac tissue within macroporous scaffolds. Neonatal rat cardiac cells were seeded into RGD-immobilized or unmodified alginate scaffolds. The immobilized RGD peptide promoted cell adherence to the matrix, prevented cell apoptosis and accelerated cardiac tissue regeneration. Within 6days, the cardiomyocytes reorganized their myofibrils and reconstructed myofibers composed of multiple cardiomyocytes in a typical myofiber bundle. The nonmyocyte cell population, mainly cardiofibroblasts, benefited greatly from adhering to the RGD–alginate matrix and con... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118538 Tue, 03 Aug 2010 23:00:00 +0100 4118538 http://www.actabiomat.org/article/PIIS174270611000351X/abstract?rss=yes Abstract: Lipid bilayers supported by nanoporous xerogel materials are being explored as models for cell membranes. In order to better understand and characterize the nature of the surface–bilayer interactions, several oxide and organic nanoporous xerogel films (alumina, titania, iron oxide, phloroglucinol–formaldehyde, resorcinol–formaldehyde and cellulose acetate) have been investigated as a scaffold for vesicle-fused 1,2-dioleoyl-glycero-3-phosphocholine (DOPC) lipid bilayer formation and mobility. The surface topography of the different substrates was analyzed using contact and tapping-mode atomic force microscopy and the surface energy of the substrates was determined using contact angle goniometry. Lipid bilayer formation has been observed with fluorescence microscopy and later... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118560 Sun, 01 Aug 2010 23:00:00 +0100 4118560 http://www.actabiomat.org/article/PIIS1742706110003533/abstract?rss=yes The objectives for this study were to characterize the phenotype of bone marrow-derived murine macrophages in response to poly(ethylene glycol) (PEG)-based hydrogels, a promising class of materials for cell delivery. Gene expression was used as a measure of phenotype and characterized by IL-1β, TNF-α, iNOS, IL-12β, arginase, VEGF-A, and IL-10. Macrophages were cultured on PEG hydrogels, PEG hydrogels with RGD tethers, and medical grade silicone rubber, a well-characterized biomaterial, up to 96h in the absence and presence of lipopolysaccharide (LPS) to simulate an inflammatory environment. Macrophage interrogation led to immediate up-regulation (10×) of IL-1β and TNF-α within 4h, followed by an increase in IL-10/IL-12β and a subsequent concomitant decrease in the pro-inflammatory g... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118535 Sun, 01 Aug 2010 23:00:00 +0100 4118535 http://www.actabiomat.org/article/PIIS1742706110003107/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3790535 Tue, 27 Jul 2010 08:17:29 +0100 3790535 http://www.actabiomat.org/article/PIIS1742706110003168/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3790534 Tue, 27 Jul 2010 08:17:28 +0100 3790534 http://www.actabiomat.org/article/PIIS1742706110003478/abstract?rss=yes Abstract: Polyethyleneimine (PEI; 25kDa)-conjugated pullulans (PPE1, PPE2 and PPE3) were developed and investigated for possible use in gene delivery applications. The cytotoxicity, blood component interactions such as red blood cell/white blood cell aggregation, platelet and complement activation, and protein interaction of the pullulan-conjugated PEI was drastically reduced in comparison to PEI-based nanocomplexes. Based on the blood compatibility studies, PPE1 was selected for further study. The buffering capacity of this derivative was similar to that of PEI, which plays an important role in efficient gene transfection. The particle size, zeta potential, stability in the presence of plasma and resistance to nuclease degradation were evaluated. In addition, cellular uptake and localizat... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118559 Sun, 25 Jul 2010 23:00:00 +0100 4118559 http://www.actabiomat.org/article/PIIS1742706110003442/abstract?rss=yes Abstract: Bisphenol A glycidylmethacrylate (BisGMA)/triethyleneglycol dimethacrylate (TEGDMA) thermosets are receiving increasing attention as biomaterials for dental and orthopedic applications; for both these fields, bacterial adhesion to the surface of the implant represents a major issue for the outcome of the surgical procedure. Moreover, the biological behaviour of these materials is influenced by their ability to establish proper interactions between their surface and the eukaryotic cells of the surrounding tissues, which is important for good implant integration. The aim of this work was to develop an antimicrobial non-cytotoxic coating for methacrylic thermosets by means of a nanocomposite material based on a lactose-modified chitosan and antibacterial silver nanoparticles. The co... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118556 Sun, 25 Jul 2010 23:00:00 +0100 4118556 http://www.actabiomat.org/article/PIIS1742706110003429/abstract?rss=yes Abstract: Small-diameter synthetic vascular graft materials fail to match the patency of human tissue conduits used in vascular bypass surgery. The foreign surface retards endothelialization and is highly thrombogenic, while the mismatch in mechanical properties induces intimal hyperplasia. Using recombinant human tropoelastin, we have developed a synthetic vascular conduit for small-diameter applications. We show that tropoelastin enhances endothelial cell attachment (threefold vs. control) and proliferation by 54.7±1.1% (3days vs. control). Tropoelastin, when presented as a monomer and when cross-linked into synthetic elastin for biomaterials applications, had low thrombogenicity. Activation of the intrinsic pathway of coagulation, measured by plasma clotting time, was reduced for tropo... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118552 Sun, 25 Jul 2010 23:00:00 +0100 4118552 http://www.actabiomat.org/article/PIIS1742706110003405/abstract?rss=yes Abstract: Silk fibroin protein is biodegradable and biocompatible, exhibiting excellent mechanical properties for various biomedical applications. However, porous three-dimensional (3-D) silk fibroin scaffolds, or silk sponges, usually fall short in matching the initial mechanical requirements for bone tissue engineering. In the present study, silk sponge matrices were reinforced with silk microparticles to generate protein–protein composite scaffolds with desirable mechanical properties for in vitro osteogenic tissue formation. It was found that increasing the silk microparticle loading led to a substantial increase in the scaffold compressive modulus from 0.3MPa (non-reinforced) to 1.9MPa for 1:2 (matrix:particle) reinforcement loading by dry mass. Biochemical, gene expression, and his... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118537 Sun, 25 Jul 2010 23:00:00 +0100 4118537 http://www.actabiomat.org/article/PIIS1742706110003417/abstract?rss=yes Abstract: The mechanical properties of the extracellular microenvironment regulate cell behavior, including migration, proliferation and morphogenesis. Although the elastic moduli of synthetic materials have been studied, little is known about the properties of naturally produced extracellular matrix. Here we have utilized atomic force microscopy to characterize the microelastic properties of decellularized cell-derived matrix from human pulmonary fibroblasts. This heterogeneous three-dimensional matrix had an average thickness of 5±0.4μm and a Young’s modulus of 105±14Pa. Ascorbate treatment of the lung fibroblasts prior to extraction produced a twofold increase in collagen I content, but did not affect the stiffness of the matrices compared with matrices produced in standard medium.... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118532 Sun, 25 Jul 2010 23:00:00 +0100 4118532 http://www.actabiomat.org/article/PIIS174270611000348X/abstract?rss=yes Abstract: Macroporous hydrogels may have direct applications in regenerative medicine as scaffolds to support tissue formation. Hydrogel microspheres may be used as drug-delivery vehicles or as building blocks to assemble modular scaffolds. A variety of techniques exist to produce macroporous hydrogels and hydrogel microspheres. A subset of these relies on liquid–liquid two-phase systems. Within this subset, vastly different types of polymerization processes are found. In this review, the history, terminology and classification of liquid–liquid two-phase polymerization and crosslinking are described. Instructive examples of hydrogel microsphere and macroporous scaffold formation by precipitation/dispersion, emulsion and suspension polymerizations are used to illustrate the nature of th... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118527 Sun, 25 Jul 2010 23:00:00 +0100 4118527 http://www.actabiomat.org/article/PIIS1742706110003491/abstract?rss=yes Abstract: Recent studies from our laboratory have shown that acellular substrates generated from human fibroblasts successfully maintained human pluripotent stem cells (hPSCs) in their undifferentiated state for extended periods. Aiming at better characterization, we conducted proteomic analyses to identify the extracellular matrix (ECM) proteins in mouse embryonic- and two human fibroblast-derived acellular substrates. Our studies identified heparan sulfate proteoglycan (HSPG) as a core component of these substrates and immunocytochemical analyses confirmed the presence of HSPG as well as other ECM proteins identified through proteomic analyses. In our attempt to develop surfaces that mimic fibroblast-deposited ECM and their self-renewal capabilities, substrates comprising HSPG and other ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097686 Sun, 25 Jul 2010 23:00:00 +0100 4097686 http://www.actabiomat.org/article/PIIS1742706110003466/abstract?rss=yes In this study the die-cast AZ91D (A for aluminum 9%, Z for zinc 1% and D for a fourth phase) and extruded WE43 (W for yttrium 4%, E for rare earth mischmetal 3%) alloys were chosen to evaluate their fatigue and corrosion fatigue behaviors in simulated body fluid (SBF). The die-cast AZ91D alloy indicated a fatigue limit of 50MPa at 107 cycles in air compared to 20MPa at 106 cycles tested in SBF at 37°C. A fatigue limit of 110MPa at 107 cycles in air was observed for extruded WE43 alloy compared to 40MPa at 107 cycles tested in SBF at 37°C. The fatigue cracks initiated from the micropores when tested in air and from corrosion pits when tested in SBF, respectively. The overload zone of the extruded WE43 alloy exhibited a ductile fracture mode with deep dimples, in comparison to a brittle fr... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097684 Sun, 25 Jul 2010 23:00:00 +0100 4097684 http://www.actabiomat.org/article/PIIS1742706110003430/abstract?rss=yes Abstract: A comparative study has been made of human and great ape molar tooth enamel. Nanoindentation techniques are used to map profiles of elastic modulus and hardness across sections from the enamel–dentin junction to the outer tooth surface. The measured data profiles overlap between species, suggesting a degree of commonality in material properties. Using established deformation and fracture relations, critical loads to produce function-threatening damage in the enamel of each species are calculated for characteristic tooth sizes and enamel thicknesses. The results suggest that differences in load-bearing capacity of molar teeth in primates are less a function of underlying material properties than of morphology. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097679 Sun, 25 Jul 2010 23:00:00 +0100 4097679 http://www.actabiomat.org/article/PIIS1742706110003454/abstract?rss=yes The objective of this study was to reveal the influence of different environmental and loading conditions on the strength of 3mol.% yttria-stabilized polycrystalline tetragonal zirconia (3Y-TZP). A total of 144 disk specimens were produced from each of two 3Y-TZP materials, and subjected to one of the following conditions: (A) no further treatment (control); (B and C) 106 and 5×106 mechanical cycles, respectively, with an upper load limit of 100N; (D) 104 thermal cycles between 5 and 55°C; (E) 200days storage in water at 36°C; (F) a successive combination of conditions B, D and E; (G) storage in water at 80°C for 64days; (H) storage in an autoclave at 134°C for 8h. Monoclinic phase content was evaluated by X-ray diffraction (XRD) analysis. Specimen strength was determined in a biaxial... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097677 Sun, 25 Jul 2010 23:00:00 +0100 4097677 http://www.actabiomat.org/article/PIIS1742706110003296/abstract?rss=yes Abstract: Repair of load-bearing defects resulting from disease or trauma remains a critical barrier for bone tissue engineering. Calcium phosphate (CaP) scaffolds are among the most extensively studied for this application. However, CaPs are reportedly too weak for use in such defects and, therefore, have been limited to non-load-bearing applications. This paper reviews the compression, flexural and tensile properties of CaPs and CaP/polymer composites for applications in bone replacement and repair. This review reveals interesting trends that have not, to our knowledge, previously been reported. Data are classified as bulk, scaffolds, and composites, then organized in order of decreasing strength. This allows for general comparisons of magnitudes of strength both within and across classi... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118526 Thu, 22 Jul 2010 23:00:00 +0100 4118526 http://www.actabiomat.org/article/PIIS1742706110003399/abstract?rss=yes Abstract: Strontium ranelate (SR) is one therapeutic option for reducing risk of fracture in osteoporosis. The effects of SR treatment on hydroxyapatite (HA) previously altered by bisphosphonate (BP) administration remain to be established. Patients who have received long-term BP treatment and present with persistent high fracture risk are of particular interest. Paired iliac crest biopsies from 15 patients post-BP therapy were subjected to a baseline biopsy and a follow-up biopsy after treatment with 2g SR day−1 after either 6months (n=5) or 12months (n=10). Dual energy X-ray absorptiometry scans, serum parameters and biochemical markers were obtained. Quantitative backscattered electron imaging and energy-dispersive X-ray analyses combined with micro-X-ray fluorescence determinations w... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097673 Thu, 22 Jul 2010 23:00:00 +0100 4097673 http://www.actabiomat.org/article/PIIS1742706110003338/abstract?rss=yes Abstract: The development of materials with biomimetic mechanical and biological properties is of great interest for regenerative medicine applications. In particular, hydrogels are a promising class of biomaterials due to their high water content, which mimics that of natural tissues. We have synthesized a hydrophilic biodegradable polymer, designated poly(glucose malate)methacrylate (PGMma), which is composed of glucose and malic acid, commonly found in the human metabolic system. This polymer is made photocrosslinkable by the incorporation of methacrylate groups. The resulting properties of the hydrogels can be tuned by altering the reacting ratio of the starting materials, the degree of methacrylation, and the polymer concentration of the resultant hydrogel. Hydrogels exhibited compres... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118533 Tue, 20 Jul 2010 23:00:00 +0100 4118533 http://www.actabiomat.org/article/PIIS174270611000334X/abstract?rss=yes Abstract: Arthropoda, which represent nearly 80% of all known animal species, are protected by an exoskeleton formed by their cuticle. The cuticle represents a hierarchically structured multifunctional biocomposite based on chitin and proteins. Some groups, such as Crustacea, reinforce the load-bearing parts of their cuticle with calcite. As the calcite sometimes contains Mg it was speculated that Mg may have a stiffening impact on the mechanical properties of the cuticle (Becker et al., Dalton Trans. (2005) 1814). Motivated by these facts, we present a theoretical parameter-free quantum-mechanical study of the phase stability and structural and elastic properties of Mg-substituted calcite crystals. The Mg-substitutions were chosen as examples of states that occur in complex chemical envir... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097672 Tue, 20 Jul 2010 23:00:00 +0100 4097672 http://www.actabiomat.org/article/PIIS1742706110003326/abstract?rss=yes Abstract: About 70% of all people with severe burns die from related infections, despite advances in treatment regimens and the best efforts of nurses and doctors. Although silver-eluting wound dressings are available for addressing this problem, there is growing evidence of the deleterious effects of such dressings in delaying the healing process owing to cellular toxicity. A new concept of antibiotic-eluting composite wound dressings is described here. These dressings are based on a polyglyconate mesh coated with a porous poly-(dl-lactic-co-glycolic acid) matrix loaded with antibiotic drugs. The effect of antibiotic release on bacterial inhibition was studied, and cell cytotoxicity was examined. The dressings resulted in a 99.99% decrease in the viable counts of Pseudomonas aeruginosa an... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118555 Mon, 19 Jul 2010 23:00:00 +0100 4118555 http://www.actabiomat.org/article/PIIS1742706110003363/abstract?rss=yes Abstract: Serum albumin was conjugated to poly-(ethylene glycol) (PEG) and cross-linked to form mono-PEGylated albumin hydrogels. These hydrogels were used as a basis for drug carrying tissue engineering scaffold materials, based on the natural affinity of various drugs and compounds for the tethered albumin in the polymer network. The results of the drug release validation experiments showed that the release kinetics of the drugs from the mono-PEGylated albumin hydrogels were controlled by the molecular weight (MW) of PEG conjugated to the albumin protein, the drug MW and its inherent affinity for albumin. Composite hydrogels containing both mono-PEGylated albumin and PEGylated fibrinogen were used specifically for three-dimensional (3D) cell culture scaffolds, with inherent bioactivity, ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118539 Mon, 19 Jul 2010 23:00:00 +0100 4118539 http://www.actabiomat.org/article/PIIS1742706110003375/abstract?rss=yes Abstract: pH-sensitive hydrogels based on methacrylic acid (MAA) and poly(ethylene glycol) macromonomer (PEGMEMA) entrapping diltiazem hydrochloride (DIL·HCl) were synthesized inside soft gelatin capsules for use as a new dosage form for oral drug administration. Different monomer compositions were used to evaluate their swelling and release behavior in two media: at low pH, simulating the acid pH of the stomach, and at pH 7, simulating the higher pH environment of the intestine. Both the swelling process and DIL·HCl release strongly depended on pH and monomer composition. Hydrogels with intermediate compositions showed diminished DIL·HCl release at pH 1.2. This fact was related to the formation of an impermeable outer skin, observed by magnetic resonance imaging (MRI). At pH 7 similar ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097689 Mon, 19 Jul 2010 23:00:00 +0100 4097689 http://www.actabiomat.org/article/PIIS1742706110003004/abstract?rss=yes The authors regret the misspelling of L.A. Hidalgo-Bastida on the author line. It is now listed correctly above. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980708 Mon, 19 Jul 2010 23:00:00 +0100 3980708 http://www.actabiomat.org/article/PIIS1742706110003259/abstract?rss=yes Abstract: There is growing interest in the use of compliant materials as an alternative to hard bearing materials such as polyethylene, metal and ceramics in artificial joints. Cushion form bearings based on polycarbonate-urethane (PCU) mimic the natural synovial joint more closely by promoting fluid-film lubrication. In the current study, we used a physiological simulator to evaluate the wear characteristics of a compliant PCU acetabular buffer, coupled against a cobalt–chrome femoral head. The wear rate was evaluated over 8 million cycles gravimetrically, as well as by wear particle isolation using filtration and bio-ferrography (BF). The gravimetric and BF methods showed a wear rate of 9.9–12.5mg per million cycles, whereas filtration resulted in a lower wear rate of 5.8mg per milli... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097694 Tue, 13 Jul 2010 23:00:00 +0100 4097694 http://www.actabiomat.org/article/PIIS1742706110003247/abstract?rss=yes Abstract: Ultraviolet (UV)-photofunctionalization of titanium substantially enhances the strength and quality of osseointegration by promoting osteogenic cellular attachment and proliferation. However, the mechanism underlying the initial interaction between the cells and the surface of the material remains to be elucidated, especially where the influence of surface roughness is excluded as a factor. The effect of UV-photofunctionalization on the adhesive strength and cellular stiffness of a single osteoblast and its association with the extent of cell spread, cytoskeletal development and focal adhesion assembly on a very smooth titanium surface was evaluated. Rat bone marrow-derived osteoblasts were cultured on UV-treated or untreated mirror-polished titanium disks. The mean critical shea... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097681 Tue, 13 Jul 2010 23:00:00 +0100 4097681 http://www.actabiomat.org/article/PIIS1742706110003065/abstract?rss=yes In conclusion, the age-specific and valve-region-specific responses of VICs to substrate stiffness link VIC phenotype to the leaflet regional matrix in which the VICs reside. These data provide further rationale for investigating the role of substrate stiffness in VIC remodeling within diseased and tissue engineered valves. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118530 Sun, 11 Jul 2010 23:00:00 +0100 4118530 http://www.actabiomat.org/article/PIIS1742706110003132/abstract?rss=yes Abstract: Soft tissue adhesives are employed to repair and seal many different organs, which range in both tissue surface chemistry and mechanical challenges during organ function. This complexity motivates the development of tunable adhesive materials with high resistance to uniaxial or multiaxial loads dictated by a specific organ environment. Co-polymeric hydrogels comprising aminated star polyethylene glycol and dextran aldehyde (PEG:dextran) are materials exhibiting physico-chemical properties that can be modified to achieve this organ- and tissue-specific adhesion performance. Here we report that resistance to failure under specific loading conditions, as well as tissue response at the adhesive material–tissue interface, can be modulated through regulation of the number and density... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118529 Sun, 11 Jul 2010 23:00:00 +0100 4118529 http://www.actabiomat.org/article/PIIS1742706110003120/abstract?rss=yes Abstract: An increased risk of late stent thrombosis associated with polymer carriers on the surface of drug-eluting stents remains one of the challenges in cardiovascular stent technology, which has instigated a renewed interest in the polymer-less, bare metal stent approach. As thrombus formation is most likely augmented by the lack of endothelial cell coverage at the exposed stented site, an improved stent surface that enhances cell coverage is essential for viable polymer-less all metal stents. We demonstrate superior endothelial cell growth, more continuous monolayer formation and overall improved endothelialization with nanopillar arrays created via radio frequency plasma surface texturing on our all metallic stent surface of MP35N stent alloy. It is shown that the nanotextured surfa... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097682 Sun, 11 Jul 2010 23:00:00 +0100 4097682 http://www.actabiomat.org/article/PIIS1742706110003077/abstract?rss=yes Abstract: Zirconia nanoparticles prepared by laser vaporization were incorporated into the primer or into the adhesive of a commercial adhesive system in order to evaluate its effect on bond strength to dentin. Zirconia nanoparticles (20–50nm) were prepared using a particular laser vaporization technique and incorporated into the primer (P) or into the adhesive (A) of the Adper Scotchbond Multi-Purpose (SBMP) system at 5, 10, 15 and 20wt.% by means of mechanical mixing (stirring) and ultrasonication. Control (unfilled) and experimental groups (filled) were applied, according to the manufacturer’s instructions, onto flat mid-coronal human dentin. Composite crowns were built up, stored in distilled water for 24h at 37°C and cut into 0.65±0.05mm2 beams following a non-trimming microtens... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097676 Sun, 11 Jul 2010 23:00:00 +0100 4097676 http://www.actabiomat.org/article/PIIS1742706110003119/abstract?rss=yes This study demonstrates that variations in the physical properties of a bone substitute material clearly influence the (extent of the) inflammatory reaction and its consequences. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097669 Sun, 11 Jul 2010 23:00:00 +0100 4097669 http://www.actabiomat.org/article/PIIS1742706110003089/abstract?rss=yes This study describes a novel twist to the traditional electrospinning technology: specifically, collector plates are designed which allow the formation of very thin layers with pore sizes suitable for cell infiltration. The thin samples could be handled without mechanically damaging the structure and could be transferred into cell culture. These thin layers were stacked layer-by-layer to develop thick structures. Thirty day cultures of fibroblasts show attachment and spreading of cells in every layer. This concept is useful in regenerating thick tissues with uniformly distributed cells and others in in vitro cell culture. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097698 Thu, 08 Jul 2010 23:00:00 +0100 4097698 http://www.actabiomat.org/article/PIIS174270611000303X/abstract?rss=yes Abstract: Evaluation of the physiological performance of biological scaffolds for tissue engineering applications has been mostly based on biophysical and morphological methods, with limited attention paid to the quantitative contribution of the main structural components to native and/or treated valve assemblies. In the present study quantitation addressed the porcine leaflet, sinus and adjacent wall of aortic and pulmonary valved conduits before and after detergent-based cell removal. Collagen, elastin, glycosaminoglycan, lipid and water contents were expressed in terms of relative concentration and volume fraction in order to assess their effective contribution to the native tissue and to changes following decellularization procedures. The main findings were recognition of unexpectedly ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097692 Thu, 08 Jul 2010 23:00:00 +0100 4097692 http://www.actabiomat.org/article/PIIS1742706110003090/abstract?rss=yes Abstract: Cellularized collagen gels are a common model in tissue engineering, but the relationship between the microstructure and bulk mechanical properties is only partially understood. Multiphoton microscopy (MPM) is an ideal non-invasive tool for examining collagen microstructure, cellularity and crosslink content in these gels. In order to identify robust image parameters that characterize microstructural determinants of the bulk elastic modulus, we performed serial MPM and mechanical tests on acellular and cellularized (normal human lung fibroblasts) collagen hydrogels, before and after glutaraldehyde crosslinking. Following gel contraction over 16days, cellularized collagen gel content approached that of native connective tissues (∼200mgml–1). Young’s modulus (E) measurements ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097690 Thu, 08 Jul 2010 23:00:00 +0100 4097690 http://www.actabiomat.org/article/PIIS1742706110003053/abstract?rss=yes Abstract: Heart failure initiated by coronary artery disease and myocardial infarction (MI) is a widespread, debilitating condition for which there are a limited number of options to prevent disease progression. Intra-myocardial biomaterial injection following MI theoretically provides a means to reduce the stresses experienced by the infarcted ventricular wall, which may alter the pathological remodeling process in a positive manner. Furthermore, biomaterial injection provides an opportunity to concurrently introduce cellular components and depots of bioactive agents. Biologically derived, synthetic and hybrid materials have been applied, as well as materials designed expressly for this purpose, although optimal design parameters, including degradation rate and profile, injectability, ela... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118525 Wed, 07 Jul 2010 23:00:00 +0100 4118525 http://www.actabiomat.org/article/PIIS1742706110003041/abstract?rss=yes In this study we fabricated a molecularly defined natural arterial graft from scratch resembling the native three layered architecture from the fibrillar extracellular matrix components collagen and elastin. Using casting, moulding, freezing and lyophilization techniques, a triple layered construct was prepared consisting of an inner layer of elastin fibres, a middle (porous) film layer of collagen fibrils and an outer scaffold layer of collagen fibrils. The construct was carbodiimide cross-linked and heparinized. Characterization included biochemical/biophysical analyses, scanning electron microscopy, micro-computed tomography, (immuno)histology and haemocompatibility. Burst pressures were up to 400mm Hg and largely conferred by the intermediate porous collagen film layer. The highly puri... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097691 Wed, 07 Jul 2010 23:00:00 +0100 4097691 http://www.actabiomat.org/article/PIIS1742706110003028/abstract?rss=yes Abstract: Wood-derived silicon carbide (SiC) offers a specific biomorphous microstructure similar to the cellular pore microstructure of bone. Compared with bioactive ceramics such as calcium phosphate, however, silicon carbide is considered not to induce spontaneous interface bonding to living bone. Bioactivation by chemical treatment of biomorphous silicon carbide was investigated in order to accelerate osseointegration and improve bone bonding ability. Biomorphous SiC was processed from sipo (Entrandrophragma utile) wood by heating in an inert atmosphere and infiltrating the resulting carbon replica with liquid silicon melt at 1450°C. After removing excess silicon by leaching in HF/HNO3 the biomorphous preform consisted of β-SiC with a small amount (approximately 6wt.%) of unreacted c... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097670 Tue, 06 Jul 2010 23:00:00 +0100 4097670 http://www.actabiomat.org/article/PIIS1742706110003016/abstract?rss=yes Abstract: The dynamic behavior of porcine brain tissue, obtained from a series of in vitro observations and experiments, is analyzed and described here with the aid of a large strain, nonlinear, viscoelastic constitutive model. Mixed gray and white matter samples excised from the superior cortex were tested in unconfined uniaxial compression within 15h post mortem. The test sequence consisted of three successive load–unload segments at strain rates of 1, 0.1 and 0.01s−1, followed by stress relaxation (n=25). The volumetric compliance of the tissue was assessed for a subset of specimens (n=7) using video extensometry techniques. The tissue response exhibited moderate compressibility, substantial nonlinearity, hysteresis, conditioning and rate dependence. A large strain kinematics nonlin... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4118531 Sun, 04 Jul 2010 23:00:00 +0100 4118531 http://www.actabiomat.org/article/PIIS1742706110002709/abstract?rss=yes In this study we have used peptide motifs that have been selected to bind to gold, platinum, glass and titanium to modify surfaces with poly(ethylene glycol) anti-fouling polymer and the integrin-binding RGD sequence. The peptides have several advantages over conventional molecular immobilization techniques; they require no biologically hostile environments to bind, are specific to their substrates and could be adapted to carry various active entities. We successfully imparted cell-resistant properties to gold and platinum surfaces using gold- and platinum-binding peptides, respectively, in conjunction with PEG. We also induced a several-fold increase in the number and spreading of fibroblast cells on glass and titanium surfaces using quartz and titanium-binding peptides in conjunction wit... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097687 Sun, 04 Jul 2010 23:00:00 +0100 4097687 http://www.actabiomat.org/article/PIIS1742706110002977/abstract?rss=yes Abstract: Amorphous calcium phosphates (ACPs) represent a unique class of biomedically relevant calcium orthophosphate salts, having variable chemical but essentially identical glass-like physical properties, in which there is neither translational nor orientational long-range ordering of the atomic positions. Normally, ACPs are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing ions of Ca2+ and ; however, other production techniques are known. Interestingly, ACPs prepared by wet-chemical techniques were found to have a relatively constant chemical composition over a relatively wide range of preparation conditions, which suggests the presence of a well-defined local structural unit, presumably with the structure of Ca9(PO4)6 – so-called Posner clust... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097668 Sun, 04 Jul 2010 23:00:00 +0100 4097668 http://www.actabiomat.org/article/PIIS1742706110002990/abstract?rss=yes Abstract: To study the role of cell–extracellular matrix (ECM) interactions, microscale approaches provide the potential to perform high throughput assessment of the effect of the ECM microenvironment on cellular function and phenotype. Using a microscale direct writing (MDW) technique, we characterized the generation of multicomponent ECM microarrays for cellular micropatterning, localization and stem cell fate determination. ECMs and other biomolecules of various geometries and sizes were printed onto epoxide-modified glass substrates to evaluate cell attachment by human endothelial cells. The endothelial cells displayed strong preferential attachment to the ECM patterned regions and aligned their cytoskeleton along the direction of the micropatterns. We next generated ECM microarrays ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097685 Thu, 01 Jul 2010 23:00:00 +0100 4097685 http://www.actabiomat.org/article/PIIS1742706110002916/abstract?rss=yes In this study, poly(vinyl alcohol) (PVA) hydrogels were reinforced with ultrahigh molecular weight polyethylene (UHMWPE) and PP fibers and evaluated as potential nondegradable meniscal replacements. An investigation of hydrogel and composite mechanical properties indicates that fiber-reinforced PVA hydrogels could replicate the unique anisotropic modulus distribution present in the native meniscus; the most commonly damaged orthopedic tissue. More specifically, fibrous reinforcement successfully increased the tensile modulus of the biomaterial from 0.23±0.02MPa without any reinforcement to 258.1±40.1MPa at 29vol.% UHMWPE. Additionally, the molecular weight between cross-links, bound water and the microstructure of the PVA hydrogels were evaluated as a function of freeze–thaw cycles and... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097696 Tue, 29 Jun 2010 23:00:00 +0100 4097696 http://www.actabiomat.org/article/PIIS1742706110002953/abstract?rss=yes Abstract: Constructs composed of cytokine-neutralizing antibodies conjugated to high-molecular-weight hyaluronic acid have been shown to be effective at controlling inflammatory responses in vivo. A critical question in the development of this new class of biomaterial is whether crosslinked conjugates have similar anti-inflammatory effects, which would open up a broad range of tissue engineering applications in which the material would have intrinsic inflammation-controlling function. To test this, high-molecular-weight hyaluronic acid was conjugated with monoclonal antibodies to the pro-inflammatory cytokines interleukin-1β and tumor necrosis factor-α in two forms of the material: viscous, non-crosslinked polymer–antibody conjugates and crosslinked, elastomeric polymer–antibody conj... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097695 Tue, 29 Jun 2010 23:00:00 +0100 4097695 http://www.actabiomat.org/article/PIIS1742706110002989/abstract?rss=yes We present an innovative methodology for the sustained delivery of hydrophobic drugs using composite hydrogels, prepared by embedding oil-in-water microemulsions in hydrophilic hydrogels. The hydrophobic nature of the microemulsion core enhances the solubilization of hydrophobic drugs, while the crosslinked matrix could be readily used as a solid controlled delivery vehicle. A microemulsion was formulated from pharmaceutical accepted components; the droplets diameter was shown to be about 10nm by dynamic light scattering, cryo-transmission electron microscopy and small-angle X-ray scattering (SAXS). Combining the microemulsion with alginate solution and crosslinking with calcium ions resulted in a clear hydrogel. A model hydrophobic drug, Ketoprofen, precipitated from the alginate hydrogel... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097688 Tue, 29 Jun 2010 23:00:00 +0100 4097688 http://www.actabiomat.org/article/PIIS174270611000293X/abstract?rss=yes We present a novel route for producing a new class of titanium foams for use in biomedical implant applications. These foams are hierarchically porous, with both the traditional large (>300μm) highly interconnected pores and, uniquely, wall struts also containing micron scale (0.5–5μm) interconnected porosities. The fabrication method consists of first producing a porous oxide precursor via a gel casting method, followed by electrochemical reduction to produce a metallic foam. This method offers the unique ability to tailor the porosity at several scales independently, unlike traditional space-holder techniques. Reducing the pressure during foam setting increased the macro-pore size. The intra-strut pore size (and percentage) can be controlled independently of macro-pore size by alteri... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097683 Tue, 29 Jun 2010 23:00:00 +0100 4097683 http://www.actabiomat.org/article/PIIS1742706110002941/abstract?rss=yes Abstract: Our objectives were to correlate the mineral density (MD) and elastic modulus (E) of natural white spot lesions (WSLs) and compare them with analytical and numerical models. Five natural WSLs from four extracted sound premolar teeth were scanned at a voxel size of 7.6μm using a desktop X-ray microtomography (XRMT) system. Five hydroxyapatite phantoms with densities ranging from 1.52 to 3.14gcm−3 were used as calibration standards for each scan. MD throughout the WSLs was quantified using an MD calibration equation derived from hydroxyapatite phantoms. Subsequently, teeth were cross-sectioned and the E modulus was measured systematically across the WSLs at intervals of 25 and 50μm using nanoindentation. The MD and E modulus of WSLs correlated well. The relationship may be expr... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097678 Tue, 29 Jun 2010 23:00:00 +0100 4097678 http://www.actabiomat.org/article/PIIS1742706110002928/abstract?rss=yes Abstract: Slow cooling firing schedules have recently been introduced by some manufacturers to reduce chipping complications in zirconia-based core/veneer composites. The aim of this study was to test the hypothesis that these firing schedules may influence the bond strength between the zirconia core and veneering ceramic. Four different veneering ceramics recommended for zirconia (Lava Ceram, Triceram, VM9 and Zirox) were fired onto rectangular shaped Y-TZP specimens (Lava Frame) and cooled using a rapid or a slow cooling rate. The resulting bilayer specimens were notched, loaded in a four-point bending test and load–displacement curves were recorded. The critical load to induce stable crack extension at the core/veneer interface was determined, in order to calculate the strain energy r... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097675 Tue, 29 Jun 2010 23:00:00 +0100 4097675 http://www.actabiomat.org/article/PIIS1742706110002965/abstract?rss=yes This study reports on the biocompatibility of composites of maghemite nanoparticles embedded in an ordered mesoporous silica-matrix to form magnetic microspheres (MMS), and on their ability to conduct magnetic hyperthermia upon exposure to a low-frequency alternating magnetic field (AMF). MMS particles were efficiently internalized by human A549, Saos-2 and HepG2 cells, and were excluded from the nuclear compartment. MMS treatment did not interfere with morphological features or metabolic activities of the cells, indicating good biocompatibility of the material. MMS did not affect the endogenous heat-shock response of a HeLa-derived cell line that precisely reports the intensity of thermal stresses through changes in the activities of a stably integrated hsp70B promoter and a constitutive ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097674 Tue, 29 Jun 2010 23:00:00 +0100 4097674 http://www.actabiomat.org/article/PIIS1742706110002904/abstract?rss=yes In this study three-dimensional nanocomposite scaffolds based on calcium phosphate (Ca-P)/poly(hydroxybutyrate–co-hydroxyvalerate) (PHBV) and carbonated hydroxyapatite (CHAp)/poly(l-lactic acid) (PLLA) nanocomposite microspheres were successfully fabricated using selective laser sintering, which is a rapid prototyping technology. The sintered scaffolds had controlled material microstructure, totally interconnected porous structure and high porosity. The morphology and mechanical properties of Ca-P/PHBV and CHAp/PLLA nanocomposite scaffolds as well as PHBV and PLLA polymer scaffolds were studied. In vitro biological evaluation showed that SaOS-2 cells had high cell viability and normal morphology and phenotype after 3 and 7days culture on all scaffolds. The incorporation of Ca-P nanoparti... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097671 Tue, 29 Jun 2010 23:00:00 +0100 4097671 http://www.actabiomat.org/article/PIIS1742706110002898/abstract?rss=yes We report here a unique strategy to fibrillate hemoglobin A (HbA), which exhibits multiple photoelectrochemical properties, and a subsequent specific defibrillation procedure. A subtle structural rearrangement of the α/β-subunits within the quaternary structure of HbA is responsible for the HbA fibril formation in the presence of 0.5% CHCl3. The narrow pH dependence of the suprastructure formation around pH 7.4 illustrates the highly sensitive nature of the structural alteration. The CHCl3-induced fibrils become disintegrated by ascorbic acid, indicating that the oxidation–reduction process of the iron within the heme moiety could be involved in stabilization of the fibrillar structures. The electron-transferring property of the iron allows the fibrils to exhibit not only their conduct... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097693 Sun, 27 Jun 2010 23:00:00 +0100 4097693 http://www.actabiomat.org/article/PIIS1742706110002874/abstract?rss=yes In this study, pulse magnetron-sputtered anatase thin films were investigated for their suitability with respect to specific biomedical applications, namely superhydrophilic and biofilm degrading implant surfaces. UV-induced hydrophilicity was quantified by static and dynamic contact angle analysis. Photocatalytic protein decomposition was analyzed by quartz crystal microbalance with dissipation. The surfaces were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The radical formation on anatase, responsible for photocatalytic effects, was analyzed by electron spin resonance spectroscopy. Results have shown that the nanocrystalline anatase films, in contrast to reference titanium surfaces, were sensitive to UV ir... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097680 Sun, 27 Jun 2010 23:00:00 +0100 4097680 http://www.actabiomat.org/article/PIIS1742706110002886/abstract?rss=yes Abstract: Calcified tissues, like bones and teeth, are among the most challenging tissues for histological research. However, especially with respect to dental or orthopaedic research, powerful histological techniques are necessary to study pathological conditions or traumatic injuries, and to investigate the molecular and cellular mechanisms of regeneration processes and functional recovery. The situation is even more complicated in orthopaedic research because here metallic implants or other devices made of various materials are often present, and the hard tissue–implant interface is of crucial interest in both biocompatibility and functional recovery research. After the cutting–grinding technique, embedding in technical resins is the most promising approach. Here we describe an opti... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980707 Sun, 27 Jun 2010 23:00:00 +0100 3980707 http://www.actabiomat.org/article/PIIS1742706110002862/abstract?rss=yes Abstract: The implantation of biomaterials may elicit a host response to this foreign body, and the magnitude of that reaction depends on the host and on the implanted material. The aim of this study was to compare the inflammatory response induced by the implantation of starch-based (SPCL) scaffolds in two implantation rat models: subcutaneous (SC) and intramuscular (IM). Moreover, two methodologies, wet spinning (WS) and fibre-bonding (FB), were used to prepare the scaffolds. The short-term inflammatory/immune host reaction was assessed by SC and IM implantations in rats after 1 and 2weeks, and the long-term host response was addressed after 8 and 12weeks of SC implantation of both types of SPCL scaffolds in rats. After each time period, the scaffolds, surrounding tissue and nearby lymph... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980693 Wed, 23 Jun 2010 23:00:00 +0100 3980693 http://www.actabiomat.org/article/PIIS1742706110002850/abstract?rss=yes Abstract: Mesenchymal stem cells (MSCs) were cultivated on the surface of nerve growth factor (NGF)-conjugated aligned nanofibrous meshes for neuronal differentiation. Amine-terminated poly(ethylene glycol) was conjugated to poly(ε-caprolactone) to prepare amine-functionalized block copolymers. The synthesized polymer was electrospun in a rotating drum to prepare aligned nanofibrous meshes. A nerve growth factor was chemically immobilized on the surface-exposed amine groups of the electrospun nanofibrous meshes in the aqueous phase. In vitro release profiles of the nerve growth factor were investigated for NGF-immobilized nanofibrous meshes. The conjugated nerve growth factor was not released for 7days, while the growth factor physically adsorbed on the nanofibrous meshes showed an initia... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=4097697 Sun, 20 Jun 2010 23:00:00 +0100 4097697 http://www.actabiomat.org/article/PIIS1742706110002795/abstract?rss=yes Abstract: In bone tissue engineering composite materials have been introduced, combining a degradable polymer matrix with, for instance, carbon nanotubes (CNTs) to improve mechanical properties or with microhydroxyapatite (μHA) to improve osteoconduction. The addition of bone morphogenetic protein-2 (BMP-2) can further improve the biological response to the material. However, the influence of such an elaborate composite formation on osteoprogenitor cells is unknown.To examine this, rat bone marrow (RBM) cells were cultured on porous poly-l-lactic acid and composite scaffolds, with or without added BMP-2. Cell proliferation and differentiation were studied using DNA, alkaline phosphatase and scanning electron microscopic analysis. Further, genetic profiles were examined by microarray inves... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980697 Sun, 20 Jun 2010 23:00:00 +0100 3980697 http://www.actabiomat.org/article/PIIS1742706110002825/abstract?rss=yes Abstract: Novel functional biodegradable gene vectors, poly(l-succinimide)-g-polyethylenimines-g-poly(ethylene glycol) (PSI-g-PEI-g-PEGs) were synthesized by conjugating methoxy poly(ethylene glycol) (mPEG, Mw=750Da) to PEI segments (Mw=800Da) of PSI-g-PEI. The physicochemical properties of PSI-g-PEI-g-PEGs, including buffering capability, pDNA binding ability, cytotoxicity, zeta potential and the particle size of polymer/pDNA complexes, were explored. The influence of PEGylation was discussed based on a comparative study of PSI-g-PEI-g-PEGs, PSI-g-PEI and PEI25k (Mw=25kDa). SEM images revealed that PSI-g-PEI-g-PEG/pDNA particles have a regular shape with the diameter ranging from 70 to 170nm. PEGylation could suppress the aggregation occurrence between complexes, resulting in a reduction ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980690 Sun, 20 Jun 2010 23:00:00 +0100 3980690 http://www.actabiomat.org/article/PIIS1742706110002837/abstract?rss=yes Abstract: Enzymatic degradation of nanoparticle (NP)-based drug delivery vehicles is a major factor influencing the administration routes as well as the site-specific delivery of NPs. To understand the stability of albumin NPs in an aggressive proteolytic environment, bovine serum albumin (BSA) NPs were fabricated via a coacervation technique and stabilized by coating using different molecular weights (MWs: 0.9–24kDa) and concentrations (0.1–1.0mgml−1) of the cationic polymer, poly-l-lysine (PLL). A short interfering ribonucleic acid (siRNA) was used as a model drug for encapsulation in the BSA NPs. The generated NPs were characterized for morphology (with atomic force microscopy), size (with photon correlation spectroscopy) and charge (zeta-potential). The size range of formed BSA p... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980689 Sun, 20 Jun 2010 23:00:00 +0100 3980689 http://www.actabiomat.org/article/PIIS1742706110002813/abstract?rss=yes In this study, the calcification-resistance efficacy and mechanical and surface properties of a new nanocomposite polymeric material (polyhedral oligomeric silsesquioxane–poly(carbonate-urea)urethane; POSS–PCU) which has been developed by our group are assessed by means of in vitro testing. In particular, thin sheets of nanocomposite, glutaraldehyde-fixed bovine pericardium (BP) and polyurethane (PU) were exposed to a calcium solution into a specially designed in vitro accelerated physiological pulsatile pressure system for a period of 31days and a total of 4×107 cycles. The samples were investigated for signs of calcification after exposure to calcium solution by means of X-ray, microscopic and chemical inspections. Mechanical and surface properties were also studied using stress–s... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980686 Sun, 20 Jun 2010 23:00:00 +0100 3980686 http://www.actabiomat.org/article/PIIS1742706110002801/abstract?rss=yes In this study, we evaluate the adhesive behaviour of skeletal muscle cells (C2C12 myoblasts) during the initial steps of spreading on layer-by-layer films of controlled stiffness made of poly(l-lysine) and hyaluronan as model biomaterial surfaces for muscle tissue engineering. We show that integrin clustering, integrin actin cytoskeleton connection and focal adhesion formation for cell spreading can be decoupled by controlling film stiffness. This made it possible to switch the cells morphologically between round and spreading shapes depending on the stiffness of the microenvironment. Although hyaluronan is one of the main components of cross-linked multilayer films, the HA receptor CD44 did not appear to mediate early adhesion as suggested by the use of blocking antibodies. In contrast, i... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980685 Sun, 20 Jun 2010 23:00:00 +0100 3980685 http://www.actabiomat.org/article/PIIS1742706110002849/abstract?rss=yes This study also investigated the influence of cyclic mechanical strain (CMS) on select molecular markers of A10 VSMCs when seeded into the optimized D-PHI scaffold. To study the interaction of A10 cells with the optimized D-PHI-75T scaffold in the presence of uniaxial strain (10%, 1Hz), a CMS bioreactor was designed and constructed. Molecular marker studies showed a statistical increase in DNA mass and calponin expression after 3 and 7days of CMS when compared to static samples, indicating that the translation of mechanical loading from the novel polyurethane elastomeric scaffold onto VSMCs will be important to consider with regard to modulating cell phenotype. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980683 Sun, 20 Jun 2010 23:00:00 +0100 3980683 http://www.actabiomat.org/article/PIIS1742706110002746/abstract?rss=yes Abstract: The uniform alignment of endothelial cells inside small-diameter synthetic grafts can be directed by surface topographies such as microgrooves and microfibers to recapitulate the flow-induced elongation and alignment of natural endothelium. These surface micropatterns may also promote directional migration and potentially improve anastomotic ingrowth of endothelial cells inside the synthetic grafts. In this paper, we developed electrospinning and spin casting techniques to pattern the luminal surface of small-diameter polyurethane (PU) grafts with microfibers and microgrooves, respectively, and evaluated endothelial cell orientation on these surface micropatterns. Tracks of circumferentially oriented microfibers were generated by electrospinning PU onto a mandrel rotated at high ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980684 Thu, 17 Jun 2010 23:00:00 +0100 3980684 http://www.actabiomat.org/article/PIIS1742706110002783/abstract?rss=yes Abstract: The advance of rapid prototyping techniques has significantly improved control over the pore network architecture of tissue engineering scaffolds. In this work, we have assessed the influence of scaffold pore architecture on cell seeding and static culturing, by comparing a computer designed gyroid architecture fabricated by stereolithography with a random pore architecture resulting from salt leaching. The scaffold types showed comparable porosity and pore size values, but the gyroid type showed a more than 10-fold higher permeability due to the absence of size-limiting pore interconnections. The higher permeability significantly improved the wetting properties of the hydrophobic scaffolds and increased the settling speed of cells upon static seeding of immortalised mesenchymal ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980682 Wed, 16 Jun 2010 23:00:00 +0100 3980682 http://www.actabiomat.org/article/PIIS1742706110002710/abstract?rss=yes Abstract: Hyperbranched poly(ester amide) polymer (Hybrane™ S1200, Mn 1200gmol−1) was functionalized with maleic anhydride (MA) and propylene sulfide, to obtain multifunctional cross-linkers with fumaric and thiol end groups, S1200MA and S1200SH, respectively. The degree of substitution (DS) of maleic acid groups was controlled by varying the molar ratio of MA to S1200 in the reaction mixture. Hydrogels were obtained by UV cross-linking of functionalized S1200 and poly(ethylene glycol) diacrylate in aqueous solutions. Compressive modulus increased with decreasing S1200/PEG ratio and also depended on the DS of the multifunctional cross-linker (S1200). Also, heparin-based macromonomers together with functionalized hyperbranched polymers were used to construct novel functional hydrogels. ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980680 Wed, 16 Jun 2010 23:00:00 +0100 3980680 http://www.actabiomat.org/article/PIIS1742706110002758/abstract?rss=yes This study demonstrates the feasibility of enhancing peri-implant osseointegration and gap bridging by immobilized rhBMP-2 on implant surfaces which may serve as a model for future clinical applications. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980703 Tue, 15 Jun 2010 23:00:00 +0100 3980703 http://www.actabiomat.org/article/PIIS1742706110002771/abstract?rss=yes In this study we electrochemically coated electrodes with biocompatible and non-cell adhesive hyaluronic acid (HA) to reduce cellular adhesion for potential use in neural prostheses. To this end, pyrrole-conjugated hyaluronic acid (PyHA) was synthesized and employed to electrochemically coat platinum, indium–tin oxide and polystyrene sulfonate-doped polypyrrole electrodes. This PyHA conjugate consisted of (1) a pyrrole moiety that allowed the compound to be electrochemically polymerized onto a conductive substrate and (2) non-adhesive HA to minimize cell adhesion and to potentially decrease inflammatory tissue responses. Our characterization results showed the presence of a hydrophilic p(PyHA) layer on the modified electrode, and impedance measurements revealed an impedance that was stat... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980702 Tue, 15 Jun 2010 23:00:00 +0100 3980702 http://www.actabiomat.org/article/PIIS1742706110002734/abstract?rss=yes Abstract: An in vitro inflation test method was developed to characterize the mechanical behavior of the bovine posterior sclera. The method used digital image correlation to provide a spatially resolved, full-field deformation map of the surface of the posterior sclera in response to controlled pressurization. A series of experiments were performed in the range of 2–6kPa (15–45mmHg) to characterize the load–unload displacement response at various pressure rates and the time-dependent displacement response at different applied pressures. The magnitude of the displacement was largest in the peripapillary region, mainly between the apex and the optic nerve head. Further, the results showed that bovine scleral tissue exhibited nonlinear and viscoelastic behavior characterized by a rate-... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980694 Tue, 15 Jun 2010 23:00:00 +0100 3980694 http://www.actabiomat.org/article/PIIS174270611000276X/abstract?rss=yes In this study, the surface of silicone rubber was solvent-free functionalized by chemical vapor deposition (CVD) of poly(o-amino-p-xylylene-co-p-xylylene (amino-PPX). Subsequently, the amino groups of the amino-PPX layer were used to introduce the initiator from a vapor phase for atom transfer radical polymerization of acrylamide to form polyacrylamide (PAAm) brushes. The modification steps were verified by means of X-ray photoelectron spectroscopy and attenuated total reflection–Fourier transform infrared spectroscopy. Adhesion of Staphylococcus aureus ATCC 12600 and Escherichia coli 3.14 to an amino-PPX–PAAm brush coating in a parallel plate flow chamber was strongly reduced with respect to non-coated silicone rubber – by 93% and 99%, respectively. For E. coli 3.14, this reduction ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980688 Tue, 15 Jun 2010 23:00:00 +0100 3980688 http://www.actabiomat.org/article/PIIS1742706110002722/abstract?rss=yes Abstract: Implant-derived material from metal-on-metal (MOM) hip arthroplasties may be responsible for an unexplained tissue inflammatory response. The chemical form of the metal species in the tissues is predominantly chromium (Cr), but the currently used techniques have not been able to determine whether this is Cr(III) phosphate or Cr(III) oxide. The analytical challenge must overcome the fact that the metal in the tissues is at a relatively low concentration and tissue preparation or the microscopy beam used can affect the results. Microfocus X-ray spectroscopy using a synchrotron beam is useful in addressing both these issues. Using this technique we compared tissue from failed MOM hips with: (1) tissue from metal-on-polyethylene (MOP) hips; (2) chemical standards; (3) metal discs cut... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980706 Thu, 10 Jun 2010 23:00:00 +0100 3980706 http://www.actabiomat.org/article/PIIS1742706110002503/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3640790 Tue, 08 Jun 2010 15:39:49 +0100 3640790 http://www.actabiomat.org/article/PIIS1742706110002680/abstract?rss=yes Abstract: Millions of people are stricken with the degenerative joint disease known as osteoarthritis. Osteoarthritis is associated with biochemical and mechanical processes, and is characterized by loss of articular cartilage and hypertrophy of bone. As cartilage and bone particles are released into the synovial fluid, a variety of biomarkers have been suggested for the analysis of this fluid. Here we have developed a method for isolating bone and cartilage wear particles suspended in the synovial fluid of the hip, knee and ankle joints of humans, based on specific magnetization of collagens I and II. Bio-ferrography is used to capture the particles on glass slides, allowing microscopic, chemical and statistical analyses. The relations between the level of the disease and the number, dime... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980705 Sun, 06 Jun 2010 23:00:00 +0100 3980705 http://www.actabiomat.org/article/PIIS1742706110002667/abstract?rss=yes Abstract: Anchorage-dependent cells respond to the mechanical and physical properties of biomaterials. One such cue is the mechanical stiffness of a material. We compared the osteogenic potential of collagen–glycosaminoglycan (CG) scaffolds with varying stiffness for up to 6weeks in culture. The mechanical stiffness of CG scaffolds were varied by cross-linking by physical (dehydrothermal (DHT)) and chemical (1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDAC) and glutaraldehyde (GLUT)) methods. The results showed that all CG substrates allowed cellular attachment, infiltration and osteogenic differentiation. CG scaffolds treated with EDAC and GLUT were mechanically stiffer, retained their original scaffold structure and resisted cellular contraction. Consequently, they facilitated a 2... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980692 Sun, 06 Jun 2010 23:00:00 +0100 3980692 http://www.actabiomat.org/article/PIIS1742706110002679/abstract?rss=yes The objective of this project was to evaluate the biological response of two different kinds of carbon fiber-reinforced (CFR) PEEK compared with ultra-high molecular weight polyethylene (UHMWPE) in vivo as a standard bearing material. Wear particles of the particulate biomaterials were injected into the left knee joint of female BALB/c mice. Assessment of the synovial microcirculation using intravital fluorescence microscopy as well as histological evaluation of the synovial layer were performed 7days after particle injection. Enhanced leukocyte–endothelial cell interactions and an increase in functional capillary density as well as histological investigations revealed that all tested biomaterials caused significantly (P0.05). These data suggest that wear debris of CFR-PEEK is comparable... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980691 Sun, 06 Jun 2010 23:00:00 +0100 3980691 http://www.actabiomat.org/article/PIIS1742706110002631/abstract?rss=yes Abstract: Pyrolytic conversion causes severe changes in the microstructure of the wood cell wall. Pine wood pyrolysed up to 325°C was investigated by transmission electron microscopy, atomic force microscopy and nanoindentation measurements to monitor changes in structure and mechanical properties. Latewood cell walls were tested in the axial, radial and tangential directions at different temperatures of pyrolysis. A strong anisotropy of elastic properties in the native cell wall was found. Loss of the hierarchical structure of the cell wall due to pyrolysis resulted in elastic isotropy at 300°C. The development of the mechanical properties with increasing temperature can be explained by alterations in the structure and it was found that the elastic properties were clearly related to len... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980696 Tue, 01 Jun 2010 23:00:00 +0100 3980696 http://www.actabiomat.org/article/PIIS1742706110002655/abstract?rss=yes Abstract: The coronary sinus (CS) vessel serves as a conduit for the deployment of percutaneous transvenous mitral annuloplasty (PTMA) devices for the treatment of functional mitral regurgitation. Characterization of the mechanical response of the CS is an important step towards an understanding of tissue–device interaction in PTMA intervention. The purpose of this study was to investigate the mechanical properties of the porcine CS using the pressure–inflation test and constitutively model the wall behavior using a four fiber family strain energy function (SEF). The results showed that the CS exhibited an S-shaped pressure–radius response and could be dilated up to 88% at a pressure of 80mmHg. Excellent results from model fitting indicated that the four fiber family SEF could captur... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980695 Tue, 01 Jun 2010 23:00:00 +0100 3980695 http://www.actabiomat.org/article/PIIS1742706110002643/abstract?rss=yes Abstract: Although biodegradable polymers have found extensive application in medical devices, there are very few commercially available elastomeric biodegradable polymers. In this work, starting with the well-known monomers l-lactide and ε-caprolactone, we developed elastomers using a multiblock co-polymer approach. This ensures that the degradation products of such elastomers are also acceptable from a cytotoxicity standpoint. A series of polymers with various structures was synthesized utilizing a design of experiment approach. The basic structure is that of a diblock, with each block being modified by the addition of co-monomer. The synthesized polymers exhibited a range of mechanical properties from a typical thermoplastic polymer to that approaching a good thermoplastic elastomer. 1... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980687 Tue, 01 Jun 2010 23:00:00 +0100 3980687 http://www.actabiomat.org/article/PIIS1742706110002576/abstract?rss=yes Abstract: A microfluidic device was used for real time imaging of MC3T3-E1 murine calvarial pre-osteoblasts (osteoblasts) in response to very small numbers of Staphylococcus epidermidis inoculated on the surface of a polished TiAl6V4 alloy in a serum-based medium. The Ti alloy surface was integrated to a poly(dimethylsiloxane) fluidic housing with eight 10μl channels for high-throughput, cross-contamination-free co-culture. In the absence of S. epidermidis osteoblasts were able to adhere, spread, proliferate and remain viable on the Ti alloy surface during a 25h culture period. With 102 or 105 colony forming units (cfu) ml−1 S. epidermidis inoculated on the alloy surface osteoblast adhesion, spreading and proliferation were not adversely affected during the early stages of culture. Howe... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980704 Sun, 30 May 2010 23:00:00 +0100 3980704 http://www.actabiomat.org/article/PIIS174270611000259X/abstract?rss=yes Abstract: The aim of this investigation was to test the in vitro performance of a self-adhesive resin composite core build-up in comparison with two typical conventional etch-and-rinse composite core build-up materials, before and after 1year of storage in 0.5% chloramine solution (LTS). Sixty human maxillary central incisors were divided into three groups. Teeth were root filled and decoronated. Specimens were restored using glass fiber posts cemented with a self-adhesive resin cement. Core build-ups were made with a self-adhesive (U) and two core build-up materials (C and L) applied with their corresponding bonding systems. All specimens received adhesively luted lithium disilicate crowns. Ten specimens of each group were exposed to LTS and examined monthly for cracks or other alteration... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980701 Sun, 30 May 2010 23:00:00 +0100 3980701 http://www.actabiomat.org/article/PIIS1742706110002588/abstract?rss=yes In this study, we show how the infiltration of biphasic calcium phosphate scaffolds with poly(ε-caprolactone) improves their mechanical properties. It was found that the polymer effectively contributes to energy to failure enhancement in bending, compressive and tensile tests. The main toughening mechanism in these composites is crack bridging by polymer fibrils. The presence of fibrils at two different size scales – as found in scaffolds with a bimodal pore distribution – results in a more effective toughening effect as compared to scaffolds with a monomodal pore size distribution, especially in the early stage of mechanical deformation. An optimized infiltration process allowed the preservation of micropore interconnection after infiltration, which is beneficial for cells adhesion. ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980699 Sun, 30 May 2010 23:00:00 +0100 3980699 http://www.actabiomat.org/article/PIIS1742706110002618/abstract?rss=yes Abstract: The effect of polymer infiltration on the compressive strength of β-tricalcium phosphate (TCP) scaffolds fabricated by robocasting (direct write assembly) is analyzed in this work. Porous structures consisting of a tetragonal three-dimensional mesh of interpenetrating rods were fabricated from concentrated TCP inks with suitable viscoelastic properties. Biodegradable polymers (polylactic acid (PLA) and poly(ε-caprolactone) (PCL)) were infiltrated into selected scaffolds by immersion of the structure in a polymer melt. Infiltration increased the uniaxial compressive strength of these model scaffolds by a factor of three (PCL) or six (PLA). It also considerably improved the mechanical integrity of the structures after initial cracking, with the infiltrated structure retaining a s... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980698 Sun, 30 May 2010 23:00:00 +0100 3980698 http://www.actabiomat.org/article/PIIS174270611000262X/abstract?rss=yes Abstract: The aim of the present study was to fabricate polycaprolactone-based nanofibrous scaffolds with incorporated protein via either the blend or coaxial electrospinning technique. Both techniques were compared with respect to processing set-up and scaffold characteristics as well as the release kinetics and biological activity of the loaded protein. Bovine serum albumin was used as a model protein to determine release profiles, while alkaline phosphatase was used to determine protein activity after the electrospinning process. Coaxial electrospinning resulted in a uniform fiber morphology with a core–shell structure, and a homogeneous protein distribution throughout the core of the fibers. In contrast, blend electrospinning formed bead-like fibers with a heterogeneous protein distr... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980681 Sun, 30 May 2010 23:00:00 +0100 3980681 http://www.actabiomat.org/article/PIIS1742706110002564/abstract?rss=yes Abstract: Mesenchymal stromal cells (MSCs) are multipotent cells that have high expansion yields and fibrin is a native extracellular matrix (ECM) material widely used for cell delivery and surgery. MSCs and fibrin have tremendous potential for tissue engineering applications, but the effect of fibrin on MSCs is not well characterized. The purpose of this study was to analyze the role of fibrin in modulating MSC phenotype by gene expression analysis. The results demonstrate that fibrin up-regulated MSC gene expression of vasculogenic (FLK1, ACTA2, VECAD, SM22 and CNN1), myogenic (MYF5 and MYH13), neurogenic (TH and GFAP) and chondrogenic (COL2A1) markers after 5days incubation. These gene expression results were supported by induction of expression on the protein level for early lineage-sp... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911529 Sun, 30 May 2010 23:00:00 +0100 3911529 http://www.actabiomat.org/article/PIIS1742706110002473/abstract?rss=yes Abstract: Glass–ceramics in the diopside (CaMgSi2O6)–fluorapatite (Ca5(PO4)3F)–wollastonite (CaSiO3) system are potential candidates for restorative dental and bone implant materials. The present study describes the influence of varying SiO2/CaO and CaF2/P2O5 molar ratio on the structure and thermal behavior of glass compositions in the CaO–MgO–SiO2–P2O5–Na2O–CaF2 system. The structural features and properties of the glasses were investigated by nuclear magnetic resonance (NMR), infrared spectroscopy, density measurements and dilatometry. Sintering and crystallization behavior of the glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. The microstructure and crystalline phase assemblage in the sintered glass powder compacts wer... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980700 Tue, 25 May 2010 23:00:00 +0100 3980700 http://www.actabiomat.org/article/PIIS174270611000245X/abstract?rss=yes This study has examined the use of polyvinylphosphonic acid (PVPA) as a potential matrix metalloproteinase (MMP) inhibitor and how brief cross-linking of demineralized dentin matrix that did not affect its mechanical properties enhanced the anti-MMP activity of PVPA. The anti-MMP potential of five PVPA concentrations (100–3000μgml–1) was initially screened using a rhMMP-9 colorimetic assay. Demineralized dentin beams were treated with the same five concentrations of PVPA to collagen and then aged for 30days in a calcium- and zinc-containing medium. The changes in modulus of elasticity, loss of dry mass and dissolution of collagen peptides were measured via three-point bending, precision weighing and hydroxyproline assay, respectively. All tested PVPA concentrations were highly effecti... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911551 Tue, 25 May 2010 23:00:00 +0100 3911551 http://www.actabiomat.org/article/PIIS1742706110002461/abstract?rss=yes Abstract: A novel visible light-crosslinkable porcine gelatin was prepared for gelation and micropatterning. The preparation employed a photo-oxidation-induced crosslinking mechanism. First, furfuryl groups were incorporated into the gelatin. Second, the modified gelatin was mixed in water with Rose Bengal, which is a visible light sensitizer. Irradiation by visible light solidified the aqueous solution. In addition, when the solution was cast on a plate, dried and photo-irradiated in the presence of a photomask a micropattern was formed that matched the micropattern on the photomask. The gelatin-immobilized regions enhanced cell adhesion. It was also confirmed that the gelatin incorporating furfuryl and Rose Bengal have no significant toxicity. The photo-crosslinkable gelatin was employed... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911535 Tue, 25 May 2010 23:00:00 +0100 3911535 http://www.actabiomat.org/article/PIIS1742706110002448/abstract?rss=yes Abstract: The biocompatibility of chitosan and its similarity to glycosaminoglycans (GAG) make it attractive for cartilage tissue engineering. We have previously reported improved chondrogenesis but limited cell adhesion on chitosan scaffolds. Our objectives were to produce chitosan scaffolds coated with different densities of type II collagen and to evaluate the effect of this coating on mesenchymal stem cell (MSC) adhesion and chondrogenesis.Chitosan fibrous scaffolds were obtained by a wet spinning method and coated with type II collagen at two different densities. A polyglycolic acid mesh served as a reference group. The scaffolds were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and type II collage... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911533 Tue, 25 May 2010 23:00:00 +0100 3911533 http://www.actabiomat.org/article/PIIS1742706110002436/abstract?rss=yes Abstract: The degradation of resorbable polymeric devices often takes months to years. Accelerated testing at elevated temperatures is an attractive but controversial technique. The purposes of this paper include: (a) to provide a summary of the mathematical models required to analyse accelerated degradation data and to indicate the pitfalls of using these models; (b) to improve the model previously developed by Han and Pan; (c) to provide a simple version of the model of Han and Pan with an analytical solution that is convenient to use; (d) to demonstrate the application of the improved model in two different poly(lactic acid) systems. It is shown that the simple analytical relations between molecular weight and degradation time widely used in the literature can lead to inadequate conclus... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911522 Sun, 23 May 2010 23:00:00 +0100 3911522 http://www.actabiomat.org/article/PIIS1742706110002412/abstract?rss=yes Abstract: The ability to trigger the formation of apatite from a supersaturated solution has been widely used to imply the bioactivity of an implant in vivo. However, the method itself may provide at best incomplete information, primarily because it is determined only by solution supersaturation, irrespective of biological processes. Bone regeneration is triggered mainly by the vitality of osteoblasts, and regulated by the expression of growth factors such as oestrogen, parathyroid hormone and bone morphogenetic proteins, while ions or other species released from an implant may affect the expression of such growth factors, and so bone resorption or formation. The misinterpretation of the outcome of such tests must result in misunderstanding of the true effects and behaviour of materials in... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3980679 Thu, 20 May 2010 23:00:00 +0100 3980679 http://www.actabiomat.org/article/PIIS1742706110002424/abstract?rss=yes Abstract: Silica–collagen bionanocomposite hydrogels were obtained by addition of silica nanoparticles to a protein suspension followed by neutralization. Electron microscopy studies indicated that larger silica nanoparticles (80nm) do not interact strongly with collagen, whereas smaller ones (12nm) form rosaries along the protein fibers. However, the composite network structurally evolved with time due to the contraction of the cells and the dissolution of the silica nanoparticles. When compared to classical collagen hydrogels, these bionanocomposite materials showed lower surface contraction in the short term (1week) and higher viability of entrapped cells in the long term (3weeks). A low level of gelatinase MMP2 enzyme expression was also found after this period. Several proteins invo... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911534 Thu, 20 May 2010 23:00:00 +0100 3911534 http://www.actabiomat.org/article/PIIS1742706110002400/abstract?rss=yes The objective of this study was to evaluate the influence of MgO and SrO doping on the mechanical and biological properties of β-tricalcium phosphate (β-TCP). β-TCP was doped with two different binary compositions, 0.25 and 1.0wt.% SrO along with 1.0wt.% MgO. MgO and SrO doping increased the β phase stability at a sintering temperature of 1250°C and marginally decreased the compressive strength of β-TCP. An in vitro cell–material interaction study, using human fetal osteoblast cells (hFOB), indicated that doped β-TCP was non-toxic, and MgO/SrO dopants improved cell attachment and growth. β-TCP implants doped with 1.0wt.% MgO and 1.0wt.% SrO showed good in vivo biocompatibility when tested in male Sprague–Dawley rats for 16weeks. Histomorphology analysis indicated that MgO/SrO-d... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911555 Wed, 19 May 2010 23:00:00 +0100 3911555 http://www.actabiomat.org/article/PIIS1742706110002394/abstract?rss=yes Abstract: Bone is composed of two phases. The organic phase is made of collagen fibrils assembled in broad fibers acting as a template for mineralization. The mineral phase comprises hydroxyapatite (HAP) crystals grown between and inside the collagen fibers. We have developed a biomimetic material using functionalized carbon nanotubes as scaffold to initiate in vitro mineralization. Biomimetic formation of HAP was performed on single-walled carbon nanotubes (SWCNTs) which have been grafted with carboxylic groups. Two types of nanotubes, HiPco® and Carbon Solutions®, were oxidized via various acidic processes, leading to five different groups of carboxylated nanotubes, fully characterized by physical methods (thermogravimetric analysis, attenuated total reflectance infrared spectroscopy a... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911548 Wed, 19 May 2010 23:00:00 +0100 3911548 http://www.actabiomat.org/article/PIIS1742706110002217/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3577215 Wed, 19 May 2010 15:30:12 +0100 3577215 http://www.actabiomat.org/article/PIIS1742706110002333/abstract?rss=yes The objective of this study was to determine the protein adsorption capability of UV-treated titanium surfaces under various electrostatic environments. The amount of albumin adsorbed on UV-treated and untreated titanium disks was evaluated under different pH conditions above and below the isoelectric points of albumin and titanium. The effects of additional treatment with various ionic solutions were also examined. Albumin adsorption on UV-treated surfaces at pH 7.0 was considerably greater (6-fold after 3h of incubation and 2.5-fold after 24h) than that to UV-untreated surfaces. UV-enhanced albumin adsorption was abrogated at pH 3.0 or when these titanium surfaces were treated with anions, while maintaining UV-induced superhydrophilicity. Albumin adsorption on UV-untreated titanium surfa... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911556 Tue, 11 May 2010 23:00:00 +0100 3911556 http://www.actabiomat.org/article/PIIS1742706110002370/abstract?rss=yes In this study, two discrete techniques were investigated. Zr was cathodically polarized in an electrolyte without calcium and phosphate ions, and Zr was cathodically polarized in another electrolyte containing calcium and phosphate ions, Hanks’ solution, to directly form a calcium phosphate layer. The surface was characterized using X-ray photoelectron spectroscopy, and the performance of the material was evaluated by immersion in Hanks’ solution. As a result, the ability to form calcium phosphate in Hanks’ solution was given by cathodic polarization in the Na2SO4 solution containing H2O2. In addition, a cathodic potential under −1.5 VSCE is required to form hydroxyapatite directly in Hanks’ solution. This research clearly reveals useful surface modification techniques giving the... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911554 Tue, 11 May 2010 23:00:00 +0100 3911554 http://www.actabiomat.org/article/PIIS174270611000228X/abstract?rss=yes Abstract: Currently, the application of nanotechnology in bone tissue regeneration is a challenge for the fabrication of novel bioartificial bone grafts. These nanostructures are capable of mimicking natural extracellular matrix with effective mineralization for successful regeneration of damaged tissues. The simultaneous electrospraying of nanohydroxyapatite (HA) on electrospun polymeric nanofibrous scaffolds might be more promising for bone tissue regeneration. In the current study, nanofibrous scaffolds of gelatin (Gel), Gel/HA (4:1 blend), Gel/HA (2:1 blend) and Gel/HA (electrospin–electrospray) were fabricated for this purpose. The morphology, chemical and mechanical stability of nanofibres were evaluated by means of field emission scanning electron microscopy (FESEM), Fourier trans... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911547 Tue, 11 May 2010 23:00:00 +0100 3911547 http://www.actabiomat.org/article/PIIS174270611000231X/abstract?rss=yes Abstract: Calcifying biological nanoparticles (NPs) develop under cell culture conditions from homogenates of diverse tissue samples displaying extraosseous mineralization, including kidney stones and calcified aneurysms. Probes to definitively identify NPs in biological systems are lacking. Therefore, the aim of this study was to begin to establish a proteomic biosignature of NPs in order to facilitate more definitive investigation of their contribution to disease. Biological NPs derived from human kidney stones and calcified aneurysms were completely decalcified by overnight treatment with ethylenediaminetetraacetic acid or brief incubation in HCl, as evidenced by lack of a calcium shell and of Alizarin Red S staining, by transmission electron microscopy and confocal microscopy, respecti... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911543 Tue, 11 May 2010 23:00:00 +0100 3911543 http://www.actabiomat.org/article/PIIS1742706110002345/abstract?rss=yes Abstract: Frictional and adhesion properties are important characteristics to be assessed in the development of new materials for biological applications, particularly for medical devices such as catheters. In this work a new computational method that predicts frictional and adhesive forces is presented. A multi-asperities adhesion model, based on the JKR theory, coupled with a Monte Carlo method was employed, together with a three components friction model. This takes into account interfacial adhesion, asperities deformation and viscous lubricant film shearing action. We have estimated the frictional coefficients of silicone and polyurethane (common materials in catheters) against aorta and vena cava. In order to do this, we have measured the surface properties of the two blood vessels ti... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911541 Tue, 11 May 2010 23:00:00 +0100 3911541 http://www.actabiomat.org/article/PIIS1742706110002357/abstract?rss=yes Abstract: Processing silk fibroin (SF) by electrospinning offers a very attractive opportunity for producing three-dimensional nanofibrillar matrices in tubular form, which may be useful for a biomimetic approach to small calibre vessel regeneration. Bypass grafting of small calibre vessels, with a diameter less than 6mm, is performed mainly using autografts, like the saphenous vein or internal mammary artery. At present no polymeric grafts made of SF are commercially available, mainly due to inadequate properties (low compliance and lack of endothelium cells). The aim of this work was to electrospin SF into tubular structures (Ø=6mm) for small calibre vessel grafting, characterize the morphological, chemico-physical and mechanical properties of the electrospun SF structures and to valida... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911537 Tue, 11 May 2010 23:00:00 +0100 3911537 http://www.actabiomat.org/article/PIIS1742706110002291/abstract?rss=yes Abstract: Designer Collagens are based on streptococcal collagen-like (Scl) proteins that form a triple helix similar to mammalian collagens but that are non-platelet aggregating. In contrast to the numerous cell-binding sites on collagen, Scl2 from Streptococcus pyogenes serotype M28 does not contain any known cell-binding sites and thus provides a blank slate in terms of cellular interactions. In the current study, Scl2 protein was modified to include receptor binding motifs that interact with α1 and/or α2 integrin subunits. The modfied Scl2 proteins have been demonstrated to mediate differential endothelial cell (EC) and smooth muscle cell (SMC) adhesion via these integrins and to retain the non-platelet aggregating properties of the “parent” Scl2. Thromboresistant scaffolds which... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911531 Tue, 11 May 2010 23:00:00 +0100 3911531 http://www.actabiomat.org/article/PIIS1742706110002321/abstract?rss=yes Abstract: Three-dimensional (3-D) in vitro models of the mammary gland require a scaffold matrix that supports the development of adipose stroma within a robust freely permeable matrix. 3-D porous collagen–hyaluronic acid (HA: 7.5% and 15%) scaffolds were produced by controlled freeze-drying technique and crosslinking with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride. All scaffolds displayed uniform, interconnected pore structure (total porosity ∼85%). Physical and chemical analysis showed no signs of collagen denaturation during the formation process. The values of thermal characteristics indicated that crosslinking occurred and that its efficiency was enhanced by the presence of HA. Although the crosslinking reduced the swelling of the strut material in water, the col... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911530 Tue, 11 May 2010 23:00:00 +0100 3911530 http://www.actabiomat.org/article/PIIS1742706110002369/abstract?rss=yes Abstract: The aim of this work was to demonstrate that conventional poly(N-isopropylacrylamide) (PNIPAAm) hydrogels can improve their shrinkage and release properties solely due to the introduction of a heterogeneous density fluctuation-based microstructure. To this end, a novel structurally engineered PNIPAAm hydrogel was designed and compared with a chemically similar, but homogeneous, PNIPAAm hydrogel reference. For the two-step preparation PNIPAAm microgels were firstly synthesized with surface amine groups and further functionalized with polymerizable acrylate groups. In the second step the microgels, themselves acting as crosslinkers, were crosslinked to form a bulk network by inter-connecting the microgels with linear PNIPAAm chains. Although the chemical composition of the newly pr... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911523 Tue, 11 May 2010 23:00:00 +0100 3911523 http://www.actabiomat.org/article/PIIS1742706110002308/abstract?rss=yes Abstract: The current study analyzes the biodegradation of a polycarbonate polyurethane scaffold intended for the growth of a tissue-engineered annulus fibrosus (AF) disc component. Electrospun scaffolds with random and aligned nanofiber configurations were fabricated using a biodegradable polycarbonate urethane with and without an anionic surface modifier (anionic dihydroxyl oligomer), and the mechanical behavior of the scaffolds was examined during a 4week biodegradation study. Both the tensile strength and initial modulus of aligned scaffolds (σ=14±1MPa, E=46±3MPa) were found to be higher than those of random fiber scaffolds (σ=1.9±0.4MPa, E=2.1±0.2MPa) prior to degradation. Following initial wetting of the scaffold, the initial modulus of the aligned samples showed a significant ... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911517 Tue, 11 May 2010 23:00:00 +0100 3911517 http://www.actabiomat.org/article/PIIS1742706110002047/abstract?rss=yes Abstract: Commonly, to determine osteoclastic resorption of biomaterials only the resorbed area is measured. The depth of the resorption pit, however, may also be important for the performance of a material. To generate such data we used two calcium phosphate ceramics (Ca10 and Ca2). The solubility of the materials was determined according to DIN EN ISO 10993-14. They were scanned three-dimensionally using infinite focus microscopy and subsequently cultivated for 4weeks in simulated body fluid without (control) or with human osteoclasts. After this cultivation period osteoclasts number was determined and surface changes were evaluated two- and three-dimensionally. Ca10 and Ca2 showed solubilities of 11.0±0.5 and 23.0±2.2mgg−1, respectively. Both materials induced a significant increase... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911550 Thu, 06 May 2010 23:00:00 +0100 3911550 http://www.actabiomat.org/article/PIIS1742706110002187/abstract?rss=yes In conclusion, hBMSCs were encapsulated in CPC and CPC–chitosan–fiber scaffolds for the first time. The encapsulated cells remained viable, osteodifferentiated and synthesized bone minerals. These self-setting, hBMSC-encapsulating CPC-based constructs may be promising for bone tissue engineering applications. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911549 Thu, 06 May 2010 23:00:00 +0100 3911549 http://www.actabiomat.org/article/PIIS1742706110002163/abstract?rss=yes Abstract: The ability of β-tricalcium phosphate (β-TCP) particles to store electric charge was confirmed by thermally stimulated depolarization current measurement as well as surface potential measurement. The efficacy of stored electrical charge on β-TCP particles in enhancing nerve regeneration was evaluated. Bridge grafting was performed into sciatic nerve defects in Wistar rats with the following tubes: chitosan mesh tubes; chitosan mesh tubes on which β-TCP particles with or without electrical polarization treatment had been immobilized (polarized and non-polarized tubes, respectively). As a control, isografts were used. Both motor and sensory nerve function as well as electrophysiological recovery progressed with time in each group. Immunofluorescence revealed rapider nerve regen... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911538 Thu, 06 May 2010 23:00:00 +0100 3911538 http://www.actabiomat.org/article/PIIS1742706110002175/abstract?rss=yes In this study, unconfined plastic compression under increasing load was used to produce collagen gels with increasing solid volume fractions. The Happel model was used to calculate the resulting permeability values in order to study the interaction of k with gel mechanical properties and mesenchymal stem cell (MSC)-induced gel contraction, metabolism and differentiation in both non-osteogenic (basal medium) and osteogenic medium for up to 3weeks. Collagen gels of fibrillar densities ranging from 0.3 to >4.1wt.% gave corresponding k values that ranged from 1.00 to 0.03μm2. Mechanical testing under compression showed that the collagen scaffold modulus increased with collagen fibrillar density and a decrease in k value. MSC-induced gel contraction decreased as a direct function of decreasing... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911532 Thu, 06 May 2010 23:00:00 +0100 3911532 http://www.actabiomat.org/article/PIIS1742706110002114/abstract?rss=yes In conclusion, sol–gel derived Na2O-containing glass ceramics have significant advantages over related Na2O-free materials, having a greatly improved combination of mechanical capability and biological absorbability. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911552 Tue, 04 May 2010 23:00:00 +0100 3911552 http://www.actabiomat.org/article/PIIS1742706110002151/abstract?rss=yes Abstract: One of the most important inconveniences of the pH- and temperature-sensitive hydrogels is the loss of thermosensitivity when relatively large amounts of a pH-sensitive monomer are co-polymerized with N-isopropylacrylamide (NIPAAm). In order to overcome this drawback, we propose here a method to prepare thermosensitive poly(vinyl alcohol) (PVA) microspheres with a higher content of carboxylic groups that preserve thermosensitive properties. Moreover, PVA possesses excellent mechanical properties, biocompatibility and non-toxicity. PVA microspheres were obtained by suspension cross-linking of an acidified aqueous solution of the polymer with glutaraldehyde. Poly(N-isopropylacrylamide-co-N-hydroxymethyl acrylamide) (poly(NIPAAm-co-HMAAm)), designed to have a lower critical solution... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911524 Tue, 04 May 2010 23:00:00 +0100 3911524 http://www.actabiomat.org/article/PIIS1742706110001881/abstract?rss=yes (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3526567 Mon, 03 May 2010 16:02:59 +0100 3526567 http://www.actabiomat.org/article/PIIS1742706110002138/abstract?rss=yes Abstract: This paper reports a new method of cross-linking electrospun zein fibers using citric acid as a non-toxic cross-linker to enhance the water stability and cytocompatibility of zein fibers for tissue engineering and other medical applications. The electrospun structure has many advantages over other types of structures and protein-based biomaterials possess unique properties preferred for tissue engineering and other medical applications. However, ultrafine fiber matrices developed from proteins have poor mechanical properties and morphological stability in the aqueous environments required for medical applications. Efforts have been made to improve the water stability of electrospun protein scaffolds using cross-linking and other approaches, but the current methods have major limi... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911540 Sun, 02 May 2010 23:00:00 +0100 3911540 http://www.actabiomat.org/article/PIIS1742706110002126/abstract?rss=yes Abstract: Chimeric proteins containing a cellulose-binding module (CBM) and an adhesion peptide (RGD or GRGDY) were produced and used to improve the adhesion of human microvascular endothelial cells (HMEC) to bacterial cellulose (BC). The effect of these proteins on the HMEC–BC interaction was studied. The results obtained demonstrated that recombinant proteins containing adhesion sequences were able to significantly increase the attachment of HMEC to BC surfaces, especially the RGD sequence. The images obtained by scanning electron microscopy showed that the cells on the RGD-treated BC present a more elongated morphology 48h after cell seeding. The results also showed that RGD decreased the in-growth of HMEC cells through the BC and stimulated the early formation of cord-like structures... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911539 Sun, 02 May 2010 23:00:00 +0100 3911539 http://www.actabiomat.org/article/PIIS1742706110002102/abstract?rss=yes Abstract: Liver targeted micelles were successfully constructed via self-assembly of glycyrrhetinic acid (GA)-modified poly(ethylene glycol)–b-poly(γ-benzyl l-glutamate) (GA–PEG–PBLG) block co-polymers, which were fabricated via ring opening polymerization of γ-benzyl l-glutamate N-carboxyanhydride monomer initiated by GA-modified PEG. The in vivo biodistribution and the in vitro cellular uptake of these micelles were investigated. The results showed that the relative uptake of doxorubicin (DOX)-loaded micelles (DOX/GA–PEG–PBLG) in liver was much higher than in other tissues, and the resulting DOX concentration in liver was about 2.2-fold higher than that from the micelles without modification by GA. Moreover, the cellular uptake study demonstrated that the introduction of GA t... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911527 Sun, 02 May 2010 23:00:00 +0100 3911527 http://www.actabiomat.org/article/PIIS174270611000214X/abstract?rss=yes In this study, we investigated the influence of different perfluoropolyether (PFPE) microstructures on the inflammatory response of human macrophages. We generated four different microstructured PFPE surfaces by replica molding from silicon masters. The function-associated surface markers 27E10 and CD163 were monitored using flow cytometry to measure the pro- and anti-inflammatory reactions. Inflammatory mediator expression was measured at the protein and mRNA level. Lipopolysaccharide treatment served as positive control for pro-inflammatory activation. We observed that each micropattern induced a specific morphology, phenotype and mediator profile. A microstructure of regular grooves induced a pro-inflammatory phenotype (M1) which was not accompanied by release of pro-inflammatory mediat... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911520 Sun, 02 May 2010 23:00:00 +0100 3911520 http://www.actabiomat.org/article/PIIS1742706110002096/abstract?rss=yes Abstract: Monoclinic tetracalcium phosphate (TTCP, Ca4(PO4)2O), also known by the mineral name hilgenstockite, is formed in the (CaO–P2O5) system at temperatures>1300°C. TTCP is the only calcium phosphate with a Ca/P ratio greater than hydroxyapatite (HA). It appears as a by-product in plasma-sprayed HA coatings and shows moderate reactivity and concurrent solubility when combined with acidic calcium phosphates such as dicalcium phosphate anhydrous (DCPA, monetite) or dicalcium phosphate dihydrate (DCPD, brushite). Therefore it is widely used in self-setting calcium phosphate bone cements, which form HA under physiological conditions. This paper aims to review the synthesis and properties of TTCP in biomaterials applications such as cements, sintered ceramics and coatings on implant met... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911515 Sun, 02 May 2010 23:00:00 +0100 3911515 http://www.actabiomat.org/article/PIIS1742706110002011/abstract?rss=yes This report aims to study the effect of glutaraldehyde (GA) cross-linking on mineralized polyanionic collagen (PAC) membranes by conducting a histological evaluation of the tissue response (biocompatibility) and by assessing the biodegradation of subcutaneous membrane implants in rats. We studied six different samples: a PAC, a PAC mineralized by alternate soaking processes for either 25 or 75 cycles (PAC 25 and PAC 75, respectively) and these films cross-linked by GA. Inflammatory infiltrate, cytokine dosage, fibrosis capsule thickness, metalloproteinase immunohistochemistry and membrane biodegradation after 1, 7, 15 and 30days were measured. The inflammatory response was found to be more intense in membranes without cross-linking, while the fibrosis capsules became thicker in cross-linke... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911536 Thu, 29 Apr 2010 23:00:00 +0100 3911536 http://www.actabiomat.org/article/PIIS1742706110001856/abstract?rss=yes The authors regret that in the above article, b was originally published with incorrect units on the x-axis. The figure with corrected x-axis units (“Time (sec)”) is reproduced below. The authors apologize to the readers of Acta Biomaterialia for the inconvenience. (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3640846 Mon, 26 Apr 2010 23:00:00 +0100 3640846 http://www.actabiomat.org/article/PIIS1742706110002035/abstract?rss=yes We report on the synthesis of thin composites of diamond-like carbon (DLC) and nanocrystalline ZrO2 deposited using pulsed direct current plasma-enhanced chemical vapor deposition at low temperatures ( (Source: Acta Biomaterialia) Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911553 Sun, 25 Apr 2010 23:00:00 +0100 3911553 http://www.actabiomat.org/article/PIIS1742706110002072/abstract?rss=yes In this study hydroxyapatite/polycaprolactone (HA/PCL) composite scaffolds were prepared by a wet chemical method at room temperature. The physico-chemical properties of the composite materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, while scaffold morphology was investigated by scanning electron microscopy (SEM) with energy-dispersive spectroscopy to validate the process used for synthesis. Finally, the response of bone marrow-derived human mesenchymal stem cells (hMSCs) in terms of cell proliferation and differentiation to the osteoblastic phenotype was evaluated using the Alamar blue assay, SEM and alkaline phosphatase activity. Microstructural analysis indicated that the HA particles were distributed homogen... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911546 Sun, 25 Apr 2010 23:00:00 +0100 3911546 http://www.actabiomat.org/article/PIIS1742706110002060/abstract?rss=yes Abstract: The stress–strain behavior of cortical bone is well known to be strain-rate dependent, exhibiting both viscoelastic and viscoplastic behavior. Viscoelasticity has been demonstrated in literature data with initial modulus increasing by more than a factor of 2 as applied strain rate is increased from 0.001 to 1500s−1. A strong dependence of yield on strain rate has also been reported in the literature, with the yield stress at 250s−1 having been observed to be more than twice that at 0.001s−1, demonstrating the material viscoplasticity. Constitutive models which capture this rate-dependent behavior from very low to very high strain rates are required in order to model and simulate the full range of loading conditions which may be experienced in vivo; particularly those invo... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911544 Sun, 25 Apr 2010 23:00:00 +0100 3911544 http://www.actabiomat.org/article/PIIS1742706110002059/abstract?rss=yes Abstract: Water striders demonstrate an amazing talent which enables them to effectively “row” across water surfaces without immobilization. This ability has previously been ascribed to the wax-like chemistry of the small hairs (setae) found on the legs, and theoretically attributed to the nano/microscaled hierarchical architecture of individual seta using the Cassie–Baxter equations. Here we show experimentally the strength of the contribution of the seta surface architecture to superhydrophobicity by maintaining identical surface chemistry (thin and thick coating of the setae with polydimethylsiloxane). Atomic force microscopy-based force and adhesion measurements of single uncoated and coated seta interacting with water quantitatively demonstrate the efficiency of the topographica... Acta Biomaterialia journals http://www.medworm.com/rss/comments.php?id=3911542 Sun, 25 Apr 2010 23:00:00 +0100 3911542