MedWorm: Materials Science

2010 Acta Materialia, Inc. Gold Medal Award

Acta Materialia — Thu, 19 Nov 2009 16:37:28 +0100

(Source: Acta Materialia)

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Editors for Acta Materialia

Acta Materialia — Thu, 19 Nov 2009 16:37:28 +0100

(Source: Acta Materialia)

Detection of polyunsaturated omega-6 fatty acid in human malignant prostate tissue by 1D and 2D high-resolution magic angle spinning NMR spectroscopy

Magnetic Resonance Materials in Physics, Biology and Medicine — Tue, 17 Nov 2009 23:49:29 +0100

Conclusion It is possible to detect PUFAs in prostate tissues using our NMR-based spectroscopic approach. Content Type Journal ArticleCategory Short CommunicationDOI 10.1007/s10334-009-0187-xAuthors Katarina Stenman, Umeå University and University Hospital of Northern Sweden Department of Radiation Sciences, Diagnostic Radiology Umeå 901 87 SwedenJón B. Hauksson, Umeå University and University Hospital of Northern Sweden Radiation Physics Umeå SwedenGerhard Gröbner, Umeå University Department of Chemistry Umeå SwedenPär Stattin, Umeå University and University Hospital of Northern Sweden Department of Surgery and Perioperative Sciences, Urology and Andrology Umeå SwedenAnders Bergh, Umeå University and University Hospital of Northern Sweden Department of Medi...

Efficient siRNA delivery to mammalian cells using layered double hydroxide nanoparticles.

Biomaterials — Mon, 16 Nov 2009 00:00:00 +0100

Authors: Ladewig K, Niebert M, Xu ZP, Gray PP, Lu GQ Although siRNAs have surpassed expectations in experiments to alter gene expression in vitro, the lack of an efficient in vivo delivery system still remains a challenge in siRNA therapeutics development and has been recognized as a major hurdle for clinical applications. In this paper we describe an inorganic nanoparticle-based delivery system that is readily adaptable for in vivo systems. Layered double hydroxide (LDH) nanoparticles, a family of inorganic crystals, tightly bind, protect, and release siRNA molecules and deliver them efficiently to mammalian cells in vitro. The uptake of siRNA-loaded LDH nanoparticles occurs via endocytosis, whereby the nanoparticles dissolve due to the low pH in the endosome, thereby aiding endosomal...

2010 Acta Materialia, Inc. Gold Medal Award

Scripta Materialia — Fri, 13 Nov 2009 16:35:00 +0100

(Source: Scripta Materialia)

Editors for Scripta Materialia

Scripta Materialia — Fri, 13 Nov 2009 16:34:59 +0100

(Source: Scripta Materialia)

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Editors for Acta Materialia

Acta Materialia — Fri, 13 Nov 2009 16:34:56 +0100

(Source: Acta Materialia)

Engineering fibrin matrices: The engagement of polymerization pockets through fibrin knob technology for the delivery and retention of therapeutic proteins.

Biomaterials — Fri, 13 Nov 2009 00:00:00 +0100

Authors: Soon AS, Stabenfeldt SE, Brown WE, Barker TH Engineering extracellular matrices that utilize the body's natural healing capacity enable the progression of regenerative therapies. Fibrin, widely used as a surgical sealant, is one such matrix that may be augmented by the addition of protein factors to promote cell infiltration and differentiation. The thrombin-catalyzed conversion of fibrinogen to fibrin exposes N-terminal fibrin knobs that bind to C-terminal pockets to form the fibrin network. Here, we have created a platform system for the production of therapeutic proteins that capitalize on these native knob:pocket interactions for protein delivery within fibrin matrices. This system enables the retention of therapeutic proteins within fibrin without additional enzymatic or ...

The effect of VEGF on the myogenic differentiation of adipose tissue derived stem cells within thermosensitive hydrogel matrices.

Biomaterials — Fri, 13 Nov 2009 00:00:00 +0100

Authors: Kim MH, Hong HN, Hong JP, Park CJ, Kwon SW, Kim SH, Kang G, Kim M We investigated the combination of human adipose tissue derived stem cells (ADSC) and in vivo gel-forming methoxy poly (ethyleneglycol)-poly (varepsilon-caprolactone) (MPEG-PCL) as a muscle regeneration matrix, with and without inclusion of vascular endothelial cell growth factor (VEGF). VEGF(165)-treated stem cell grafts showed significant proliferation and differentiation into muscle tissue in vivo. Importantly, the inclusion of VEGF enhanced vascularization. This scaffold supported preconditioned ADSC, and allowed them to differentiate into mature muscle tissues in vivo, indicating that ADSC of human origin and MPEG-PCL scaffolds provided an appropriate environment for cellular growth and expansion. Our resul...

The induction of tumor apoptosis in B16 melanoma following STAT3 siRNA delivery with a lipid-substituted polyethylenimine.

Biomaterials — Thu, 12 Nov 2009 00:00:00 +0100

In this study, we investigated the potential of nanoparticles based on polyethylenimine (PEI) modified with stearic acid (StA), to deliver siRNA for efficient STAT3 downregulation in B16 melanoma cells. The B16 cells were targeted with approximately 6-200nm of siRNA complexes for 36h. Compared to the PEI complexes, the PEI-StA complexes showed higher potency in STAT3 silencing in B16 cells accompanied by a significant induction of IL-6 secretion and a reduction of VEGF production. Moreover, with PEI-StA complexes, the level of the cellular Caspase 3 activity (an indicator of apoptotic activity) was found to be 2.5 times higher than that of PEI complexes. When the cells were treated with 50nm of siRNA complexes on a daily basis, the cell viability was dramatically reduced reaching only to 1...

The effect of timing in the administration of hepatocyte growth factor to modulate BMP-2-induced osteoblast differentiation.

Biomaterials — Wed, 11 Nov 2009 00:00:00 +0100

This study analyzed osteogenic properties of HGF, particularly during BMP-2-induced bone formation. Using a mouse model of ectopic bone formation, HGF-impregnated gelatin sponges displayed significantly reduced bone formation induced by BMP-2, both radiologically and histologically. Abrogation of endogenous HGF production by knockdown of HGF mRNA resulted in upregulation of BMP-2-induced ALP activity for C2C12 myoblasts in vitro. In contrast, addition of exogenous HGF inhibited BMP-2-induced ALP activity and osteocalcin production by mouse embryonic fibroblasts (MEFs) through HGF-c-Met interactions. Inhibition of ALP activity by HGF was rescued by U0126, a MEK1/2 inhibitor, indicating that HGF suppresses the BMP-2-Smad axis via activation of ERK1/2. Importantly, treatment with HGF prior to...

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A nitric oxide releasing, self assembled peptide amphiphile matrix that mimics native endothelium for coating implantable cardiovascular devices.

Biomaterials — Wed, 11 Nov 2009 00:00:00 +0100

Authors: Kushwaha M, Anderson JM, Bosworth CA, Andukuri A, Minor WP, Lancaster JR, Anderson PG, Brott BC, Jun HW Cardiovascular disease is the number one cause of death in the United States. Deployment of stents and vascular grafts has been a major therapeutic method for treatment. However, restenosis, incomplete endothelialization, and thrombosis hamper the long term clinical success. As a solution to meet these current challenges, we have developed a native endothelial ECM mimicking self-assembled nanofibrous matrix to serve as a new treatment model. The nanofibrous matrix is formed by self-assembly of peptide amphiphiles (PAs), which contain nitric oxide (NO) donating residues, endothelial cell adhesive ligands composed of YIGSR peptide sequence, and enzyme-mediated degradable sites...

Immunological response to tissue-engineered cartilage derived from auricular chondrocytes and a PLLA scaffold in transgenic mice.

Biomaterials — Wed, 11 Nov 2009 00:00:00 +0100

Authors: Fujihara Y, Takato T, Hoshi K The immune response against biomaterials in tissue-engineered constructs could potentially worsen the outcome of tissue regeneration, but immunological reactions between host and donor in tissue-engineered constructs remain to be clarified. In the present study, we syngenically transplanted tissue-engineered cartilage constructs consisting of C57BL/6 mice auricular chondrocytes and poly-l-lactic acid scaffolds (MW:200,000) into EGFP transgenic mice of C57BL/6 background, and evaluated the response by the localization of donor-derived and host-derived cells, the latter of which were distinguished by the presence of EGFP. While donor-derived cells constituted the areas of regenerated cartilage, host-derived cells were increased in number for the ini...

Dinuclear metal(II) complexes of polybenzimidazole ligands as carriers for DNA delivery.

Biomaterials — Mon, 09 Nov 2009 00:00:00 +0100

Authors: Liu L, Zhang H, Meng X, Yin J, Li D, Liu C A metal-based nonviral carrier for DNA-transfer in gene therapy was synthesized and characterized. The strong intermolecular pi-pi contacts are common in the observed dinuclear Cu(2+) and Co(2+) complexes of polybenzimidazole ligands. The affinity assays indicated that the strong binding of the complexes to DNA is driven by both electrostatic attractions between the complexes and DNA and the intercalation of the ligands between DNA base pairs. The typical in vitro studies showed that micromolar doses of each complex tested can efficiently and rapidly condense free DNA, either in linear or circular state, from solutions into well defined and globular nanoparticles with varied sizes. Therefore, the formation and dissociation of the DNA ...

Self-initiated surface grafting with poly(2-methacryloyloxyethyl phosphorylcholine) on poly(ether-ether-ketone).

Biomaterials — Mon, 09 Nov 2009 00:00:00 +0100

Authors: Kyomoto M, Moro T, Takatori Y, Kawaguchi H, Nakamura K, Ishihara K Poly(ether-ether-ketone) (PEEK)s are a group of polymeric biomaterials with excellent mechanical properties and chemical stability. In the present study, we demonstrate the fabrication of an antibiofouling and highly hydrophilic high-density nanometer-scaled layer on the surface of PEEK by photo-induced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) without using any photo-initiators, i.e., "self-initiated surface graft polymerization." Our results indicated that the diphenylketone moiety in the polymer backbone acted as a photo-initiator similar to benzophenone. The density and thickness of the poly(MPC) (PMPC)-grafted layer were controlled by the photo-irradiation time and monomer conc...

The role of protein assembly in dynamically tunable bio-optical tissues.

Biomaterials — Mon, 09 Nov 2009 00:00:00 +0100

Authors: Tao AR, Demartini DG, Izumi M, Sweeney AM, Holt AL, Morse DE Cephalopods are nicknamed the "masters of disguise" for their highly evolved camouflage mechanisms, including the hallmark ability to rapidly change the color and reflectance of their skin. Previously, reflectin proteins were identified as the major biomaterial component of iridosomes [1], specialized light-reflecting architectures that contribute intense structural color to squid skin, eyes, and organs [2-5]. Supramolecular assembly of reflectin has been recognized as a key property in the protein's function [6]. Here, we report the first cloning and expression of a specific reflectin protein found in the responsive iridophore cells of the squid Loligo pealeii, which are unique in their ability to switch on/off and ...

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Effects of VEGF temporal and spatial presentation on angiogenesis.

Biomaterials — Mon, 09 Nov 2009 00:00:00 +0100

Authors: Silva EA, Mooney DJ Therapeutic angiogenesis relies on the delivery of angiogenic factors capable of reversing tissue ischemia. Polymeric materials that can provide spatial and temporal over vascular endothelial growth factor (VEGF) presentation provide clear benefit, but the influence of VEGF dose, temporal, and spatial presentation on the resultant angiogenic process are largely unknown. The influence of the temporal profile of VEGF concentration, dose, and the impact of VEGF spatial distribution on angiogenesis in in vitro models of angiogenesis and ischemic murine limbs was analyzed in this study. Importantly, a profile consisting of a high VEGF concentration initially, followed by a decreasing concentration over time was found to yield optimal angiogenic sprouting. A tota...

Study of the adhesion improvement in hippocampal cells on collagen/chitosan- modified silicon surfaces

Biomedical Materials — Mon, 09 Nov 2009 00:00:00 +0100

Author(s): Yi Zhao, Xiaoying Lu, Zhigong Wang, Yan Huang, Zhenglin Jiang and Xia LiAffiliation(s): State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, People's Republic of China; Institute of RF- & OE-ICs, Southeast University, Nanjing 210096, People's Republic of China; Key Lab of Neural Regeneration of Jiangsu Province, Nantong University, Nantong 226001, People's Republic of China; Author to whom any correspondence should be addressed (Source: Biomedical Materials)

A biomimetic hydrogel based on methacrylated dextran-graft-lysine and gelatin for 3D smooth muscle cell culture.

Biomaterials — Fri, 06 Nov 2009 00:00:00 +0100

This study reports synthesis of a methacrylate and lysine functionalized dextran and development of hydrogel composite systems based on this material and methacrylamide modified gelatin. The mechanical stiffness and degree of swelling of the hydrogels were varied by manipulation of the degree of functionalization of dextran and gelatin and concentration/composition of precursor solution. Human umbilical artery smooth muscle cells (SMCs) were encapsulated inside hydrogels during gel hardening with photopolymerization. Rapid cell spreading, extensive cellular network formation and high SMC proliferation occurred within softer hydrogels (with shear storage moduli ranging from 898 to 3124Pa). The encapsulated SMCs appear to be relatively contractile in the initial culture than on tissue cultur...

Different types of article in JMBBM.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:51 +0100

Authors: Taylor D PMID: 19878896 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials)

Effect of fluorapatite additive on densification and mechanical properties of tricalcium phosphate.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:48 +0100

Authors: Bouslama N, Ben Ayed F, Bouaziz J Tricalcium phosphate and synthesized fluorapatite powder were mixed in order to elaborate biphasic composites. The samples were characterized by X-ray diffraction, differential thermal analysis, infrared spectroscopy, scanning electron microscopy and by an analysis using (31)P nuclear magnetic resonance. The sintering of tricalcium phosphate with different percentages of fluorapatite (13.26 wt%; 19.9 wt%; 33.16 wt% and 40 wt%) indicates the evolution of the microstructure, densification and mechanical properties. The Brazilian test was used to measure the rupture strength of the sintered biphasic composites. The mechanical properties increase with the sintering temperature and with the addition of fluorapatite additive. The mechanical resistan...

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An entropy spring model for the Young's modulus change of biodegradable polymers during biodegradation.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:45 +0100

Authors: Wang Y, Han X, Pan J, Sinka C This paper presents a model for the change in Young's modulus of biodegradable polymers due to hydrolysis cleavage of the polymer chains. The model is based on the entropy spring theory for amorphous polymers. It is assumed that isolated polymer chain cleavage and very short polymer chains do not affect the entropy change in a linear biodegradable polymer during its deformation. It is then possible to relate the Young's modulus to the average molecular weight in a computer simulated hydrolysis process of polymer chain sessions. The experimental data obtained by Tsuji [Tsuji, H., 2002. Autocatalytic hydrolysis of amorphous-made polylactides: Effects of L-lactide content, tacticity, and enantiomeric polymer blending. Polymers 43, 1789-1796] for poly...

Minimizing specimen length in elastic testing of end-constrained cancellous bone.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:42 +0100

Authors: Lievers WB, Waldman SD, Pilkey AK End-constraint is needed when performing tensile and compressive testing of cancellous bone so that frictional and structural end-effects are minimized and the mechanical properties are not underestimated. Since many end-constrained testing techniques are limited to certain sites and species by the large specimen sizes required, reductions in overall specimen length would be advantageous. The following study examines the effect of specimen gauge length and aspect ratio on the elastic tensile testing of cancellous bone from the bovine femoral condyle. Three different nominal gauge lengths (10, 16, 22 mm) were examined at two different diameters (5.1, 10.7 mm) which bound the range typically used for cancellous bone testing. No effect of gauge l...

Mechanical evaluation by patient-specific finite element analyses demonstrates therapeutic effects for osteoporotic vertebrae.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:40 +0100

Authors: Tawara D, Sakamoto J, Murakami H, Kawahara N, Oda J, Tomita K Osteoporosis can lead to bone compressive fractures in the lower lumbar vertebrae. In order to assess the recovery of vertebral strength during drug treatment for osteoporosis, it is necessary not only to measure the bone mass but also to perform patient-specific mechanical analyses, since the strength of osteoporotic vertebrae is strongly dependent on patient-specific factors, such as bone shape and bone density distribution in cancellous bone, which are related to stress distribution in the vertebrae. In the present study, patient-specific general (not voxel) finite element analyses of osteoporotic vertebrae during drug treatment were performed over time. We compared changes in bone density and compressive princip...

Development of biomedical porous titanium filled with medical polymer by in-situ polymerization of monomer solution infiltrated into pores.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:37 +0100

In this study, for the fabrication of the abovementioned composite, a versatile process for filling a medical polymer into a porous metallic material has been developed using porous pure titanium (pTi) and polymethylmethacrylate (PMMA). Then, the tensile strength and Young's modulus of pTi filled with PMMA (pTi/PMMA) fabricated using this process are systematically investigated. The tensile strength of pTi can be improved by the PMMA filling. Particularly, the improvement in the tensile strength of pTi pretreated using a silane coupling agent before PMMA filling is greater than that of the non-pretreated pTi because the stress concentration near the pores may be reduced by the improvement in the interfacial adhesiveness between the titanium particles and the PMMA. In contrast, the effect o...

Mechanical characterisation of polyurethane elastomer for biomedical applications.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:34 +0100

Authors: Kanyanta V, Ivankovic A Mechanical testing and modelling of a material for biomedical applications have to be based on conditions representative of the application of interest. In this work, an ether-based polyurethane elastomer is used to build mock arteries. The aim is to study the behaviour of arteries under pulsatile loading conditions and how that behaviour changes with the development and progression of atherosclerosis. Polyurethane elastomers are widely used as biomaterials, e.g. in tube form for bypasses and catheters. However, their mechanical behaviour has not been extensively characterised. This work establishes the variations in the behaviour of polyurethane elastomer with temperature, humidity and strain rate and also reports planar and equibiaxial tension, relaxa...

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Investigation of the mechanical interaction of the trabecular core with an external shell using rapid prototype and finite element models.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:31 +0100

The objective of this study was to investigate this interaction and to determine what effect it has on the ultimate strength of the whole bone. This objective was achieved by compression testing rapid prototype (RP) models of cylindrical trabecular bone cores, with and without an integral surrounding shell and incorporating increasing levels of artificially induced bone loss. Corresponding finite element (FE) models were generated and the load sharing of the shell and trabecular core was analysed under linear elastic loading conditions. The results of the physical RP model tests and corresponding FE analyses indicated that there was a reinforcing effect between the cortical shell and the trabecular core for all models tested and that the reinforcing effect became relatively more important ...

Wear behavior of light-cured dental composites filled with porous glass-ceramic particles.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:28 +0100

In this study, novel bioactive glass-ceramic powders exhibiting different nominal calcium-mica to fluorapatite ratios were used as fillers for light-cured dental composites. Wear tests on the resulting samples were undertaken using a micro-tribometer with a linear reciprocating ball-on-flat geometry using lubrication from artificial saliva. The surfaces of the worn composites were then evaluated using optical microscopy. In order to enhance matrix bonding, the surfaces of the different particulates were treated using hydrofluoric acid to provide a porous surface and the resulting surface morphology was evaluated using scanning electron microscopy. Although in the case of the samples containing low fluorapatite contents (20 wt%; A2), surface etching enhanced the wear resistance of the compo...

A novel constitutive model of skeletal muscle taking into account anisotropic damage.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:25 +0100

Authors: Ito D, Tanaka E, Yamamoto S The purpose of this study is to develop a constitutive model of skeletal muscle that describes material anisotropy, viscoelasticity and damage of muscle tissue. A free energy function is described as the sum of volumetric elastic, isochoric elastic and isochoric viscoelastic parts. The isochoric elastic part is divided into two types of shear response and the response in the fiber direction. To represent the dependence of the mechanical properties on muscle activity, we incorporate a contractile element into the model. The viscoelasticity of muscle is modeled as a three-dimensional model constructed by extending the one-dimensional generalized Maxwell model. Based on the framework of continuum damage mechanics, the anisotropic damage of muscle tissu...

Dependence of in vitro fatigue properties of PMMA bone cement on the polydispersity index of its powder.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:22 +0100

Authors: Lewis G, Li Y Four variants of poly (methyl methacrylate) (PMMA) bone cement were used, the difference being in the method used to sterilize the powder (three different dosages of gamma irradiation and ethylene oxide gas) and, hence, in the molecular weight of the powder. For each cement powder, the number-average molecular weight and weight-average molecular weight (and, hence, the polydispersity index, PDI) were determined using gel permeation chromatography. For each of the cured cements, the fatigue lives (N(f)) of specimens, at loads corresponding to stresses (S) of +/-10.0 MPa, +/-12.5 MPa, +/-15.0 MPa, and +/-20.0 MPa, were determined using the protocol detailed in ASTM F2118-03. Hence, the values of the three Weibull parameters were determined for each cement set-S com...

Anisotropic swelling and mechanical behavior of composite bacterial cellulose-poly(acrylamide or acrylamide-sodium acrylate) hydrogels.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:19 +0100

Authors: Buyanov AL, Gofman IV, Revel'skaya LG, Khripunov AK, Tkachenko AA Bacterial cellulose-polyacrylamide (BC-PAAm) composite hydrogels are prepared by synthesis of PAAm networks inside the BC matrices. The behavior of these gels and of the ionic ones obtained via partial hydrolysis of BC-PAAm gels is studied under swelling and compressive deformation conditions. The dependences of the hydrogels' properties on the BC matrix preparation conditions, gel synthesis conditions and the BC content in the hydrogel compositions are studied. Two types of BC gel pellicle are used in the hydrogel synthesis, namely matrix pellicles subjected to pre-pressing (samples of series A) and those not subjected to any mechanical actions before synthesis (series B samples) containing about 99% water. The...

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Viscoelastic behavior of discrete human collagen fibrils.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:17 +0100

In conclusion, the present work provides direct evidence of viscoelastic behavior at the single fibril level, which has not been previously measured. PMID: 19878908 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials)

Fracture of tooth enamel from incipient microstructural defects.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:14 +0100

We present definitive evidence for crack growth from internal defects called 'tufts' in human enamel. Transverse slices (normal to the tooth axis) sawn from extracted human teeth are embedded in a polycarbonate sandwich configuration and tested in simple flexural loading. The evolution of ensuing cracks across the enamel sections is viewed in situ by a video camera. The observations unequivocally identify tufts as sources of internal tooth fracture. In sufficiently thin slices the enamel becomes translucent, allowing for through-thickness observations of the crack topography. Crack segments that appear to be disjointed on a section surface link up into a contiguous primary crack below the surface, suggesting some crack resistance by 'bridging' behind the advancing crack tip. The role of th...

Friction of F-actin knots.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:11 +0100

Authors: Kirchner HO, Neukirch S We use the existing data of force-extension experiments on F-actin molecules tied into knots to compute a value of 0.15 for the static friction coefficient for contact between different parts of the same molecule with itself. This estimate for protein-protein friction is relevant for the stabilization of the 273 known proteins with knots, one percent of the structures deposited in the Protein Data Bank. PMID: 19878910 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials)

Transversely isotropic tensile material properties of skeletal muscle tissue.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:08 +0100

Authors: Morrow DA, Haut Donahue TL, Odegard GM, Kaufman KR Of the plethora of work performed analyzing skeletal muscle tissue, relatively little has been done in the examination of its passive material properties. Previous studies of the passive properties of skeletal muscle have been primarily performed along the longitudinal material direction. In order to ensure the accuracy of the predictions of computational models of skeletal muscles, a better understanding of the tensile three-dimensional material properties of muscle tissue is necessary. To that end, the purpose of this study was to collect a comprehensive set of tensile stress-strain data from skeletal muscle tissue. Load-deformation data was collected from eighteen extensor digitorum longus muscles, dissected free of aponeur...

A composite kidney stone phantom with mechanical properties controllable over the range of human kidney stones.

Journal of the Mechanical Behavior of Biomedical Materials — Tue, 03 Nov 2009 22:46:05 +0100

Authors: Simmons WN, Cocks FH, Zhong P, Preminger G A novel composite kidney stone phantom has been developed. This stone phantom is producible with mechanical properties mimicking the range of tensile fracture strength and acoustic properties of human kidney stones and is an inorganic/organic composite material, as are natural kidney stones. Diametral compression testing was used to measure tensile fracture strength, which determines the acoustic comminution behavior of kidney stones. Ultrasound transmission tests were made to characterize the acoustic properties of these stone phantoms. Both the tensile fracture strength (controllable from 1 to approximately 5 MPa) and acoustic properties (C(L) = 2700-4400 m/s and C(T)=1600-2300m/s) of these composite phantom stones match those of a ...

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Statistical Analysis of Misorientation Distributions From Growth Selection Experiments in Iron–3% Si

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

The frequency of occurrence of differently misoriented grain boundaries in growth selection experiments in silicon–iron was reported by Ibe and Lücke and has been the basis of many texture models. However, this pattern of behaviour bears much similarity to misorientation frequencies calculated from random textures. A comparison of the experimental and computed frequency distribution shows that there are statistically significant differences and therefore that some possibilities for growth selection do exist (Source: Texture, Stress, and Microstructure)

Microstructure and Texture of in Situ Heavily Drawn Cu–Nb Composites

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

Heavily cold drawn in situ Cu–Nb composites have been investigated by transmission electron microscopy (TEM) and X-ray analysis. Dislocation density in the copper matrix has been shown to change only slightly in the investigated drawing ratio range because of the development of stage IV of deformation. In Nb filaments dislocation density in the investigated range at first increases with deformation and then drops at the highest drawing ratio. At intermediate deformation niobium grains consist of fine blocks separated by low-angle dislocation boundaries. At drawing, fibre texture develops in both phases, with 〈111〉 and 〈100〉 axis for the copper matrix and 〈110〉 axis for niobium filaments. Besides, niobium filaments acquire ribbon-like form...

Influence of Rolling Temperature on the Perfection Degree of Recrystallization Cube Texture in Nickel

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

The effect of the rolling temperature on the deformation texture and the perfection degree of a cube texture in pure-nickel thin tape were investigated. The kinetics of primary recrystallization was studied on samples that had undergone rolling at different temperatures and the temperature of the onset of secondary recrystallization was determined. Regularities of the structure formation in the samples are discussed. It is established that the cube texture with the maximum sharpness is produced in the samples rolled at room temperature. (Source: Texture, Stress, and Microstructure)

Effect of Zonal Isolation on the Kinetics of Sintering a Particulate Body

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

This paper describes the so-called meso-scale simulations of sintering a particulate body. Computations were made using 3D structure-imitation computer model of evolution of a powder compact during sintering. It was demonstrated, that in powder bodies the effect of zonal isolation (forming separate groups of particles during sintering) determines features of shrinkage and internal structure of a compact. In case of the diffusion- viscous flow of particles the fact was proved that the zonal isolation is predetermined by ratio of viscosity and free surface energy. It was verified, that there is a critical value of the above ratio with respect to which the balance of internal structure- creating processes is determined. (Source: Texture, Stress, and Microstructure)

Quantification of Minor Texture Components by Hard X-Rays

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

Non-destructive methods to determine the volume fraction of minor texture components with very low reflection intensities are presented. The methods are based on polycrystalline diffraction of hard X-rays from synchrotron sources. By focusing the X-rays and scanning the specimen, it is shown that volume fractions as low as 10-9 can be registered, provided that the crystallographic orientations of such volume elements are far away from any major texture component. Simultaneously, the spatial resolving power is of the order 0.03 μm3. The relevance of such methods for nucleation studies and trace analysis is outlined. (Source: Texture, Stress, and Microstructure)

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Recrystallization in a Hot Deformed Al-Mg-Si Alloy: The Effect of Fine Precipitates

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

The recrystallization of an Al-Mg-Si alloy deformed by plane strain compression at 400°C and 1 s-1 has been studied. Fine particles are found to have a significant influence on the development of recrystallization textures. Annealing at 400°C, in the presence of Al-Fe-Si particles located on boundaries, results in a weak recrystallization texture. There is a clear indication that grain nucleation is associated with abnormal subgrain growth. The occurrence of this recovery process is analyzed by taking into account the particle pinning pressure and the orientation dependence of boundary energy and mobility. The cube recrystallization texture observed after annealing at 510°C is discussed in terms of the stability of Mg2Si and Al-Fe-Si precipitates. (Source: Texture, Stress, a...

Microtexture Studies of PST and PZT Ceramics and PZT Thin Film by Electron Backscatter Diffraction Patterns

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

Crystallographic orientations of twelve different lead scandium tantalate (PST) ceramics, two lead zirconate titanate ceramics (PZT) and one PZT thin film were investigated by the technique of electron backscatter diffraction (EBSD) in the scanning electron microscope. The PST ceramics were processed under different conditions of temperature and annealing. Crystal orientations in the bulk ceramics were examined and the results were plotted in microtexture pole- and inverse pole-figures. Local texture and misorientation between adjacent grains in certain selected regions of the ceramics were also examined. To compare the results of the PST with another lead-based ferroelectric material, an unpoled and a poled PZT ceramics were studied for their texture. The electrical and electromechanical ...

On The Peculiarities of X-Ray Determination of Crystallographic Texture in Samples After Testing Wear Resistance

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

A peculiar relief generally appears on the sample surface while testing wear resistance, which impairs the results of texture analysis by X-ray diffraction methods. The main reason for this is screening influence of the surface roughness on the X-ray passing through. From model representations, the influence on the screening of the relief parameters and the characteristic angle of reflection of X-rays is shown. Distribution of the parameters of a relief that actually forms is analyzed. A computer-assisted method of calculation of pole figures that excludes the screening effect is suggested. As an example of the method of application, the results of the analysis of textures that form upon testing wear resistance under condition of dry friction by slipping in pairs of samples of the β-...

Effective Elastic Properties of Textured Cubic Polycrystals

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

A general scheme for the solution of problem of averaging elastic properties of textured polycrystals is suggested which is based on the algebraic methods of description of elastic properties. (Source: Texture, Stress, and Microstructure)

Pole Figure Inversion Using Finite Elements Over Rodrigues Space

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

Using finite elements over Rodrigues space, methods are developed for the formation and inversion of pole figures. The methods take advantage of the properties of Rodrigues space, particularly the fact that geodesics corresponding to pole figure projection paths are straight lines. Both discrete and continuous pole figure data may be inverted to obtain orientation distribution functions (ODFs) in Rodrigues space, and we include sample applications for both types of data. (Source: Texture, Stress, and Microstructure)

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Preface

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

(Source: Texture, Stress, and Microstructure)

Depth Resolved Strain and Phase Mapping of Dissimilar Friction Stir Welds Using High Energy Synchrotron Radiation

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

The strain and phase distribution in a dissimilar friction stir weld of AA6082-T6 to AA2024-T3 is investigated non-destructively. The measurements are performed using a novel depth resolved strain and phase mapping technique. The technique is based on the use of a focussed high energy synchrotron beam, a novel spiral slit system, and an area detector system. Through thickness measurements of the residual strain along the weld centre show strong variations with changes of sign. The strain scans across the weld exhibit a strong asymmetry in particular for the longitudinal strain component. A depth resolved strain mapping across the weld shows for the dominant longitudinal strain component variations in depth, especially on the AA6082 side of the weld. Results from the strain measurements are...

Tensile Deformation Induced Texture Transformation in Austenitic Stainless Steel

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

Texture patterns of the starting ώ and transformed α structural phases were obtained from AISI 304 stainless steel sheets subjected to varying levels of tensile deformation using high energy X-ray diffraction in combination with the texture enhanced Rietveld method. The use of this method allows the simultaneous determination of the orientation distribution functions (ODF) of both phases, even for small α-martensite fractions of the order of 5%. The texture patterns are analyzed in terms of the crystallographic orientation relation between the starting and transformed phases and the preferential formation of certain variants of this relation. (Source: Texture, Stress, and Microstructure)

Torsion Texture Measurements With High-Energy Synchrotron Radiation on NiAl

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

Diffraction with high-energy synchrotron radiation is a new experimental method to determine textures of materials, which due to the special properties of this radiation, in the future may have advantages in terms of accuracy of local texture measurements in comparison to established methods like Electron back scatter diffraction (EBSD). In the present study NiAl polycrystals with two different initial textures have been deformed in torsion at 727°C and 1000°C and their texture development has been measured with highenergy synchrotron radiation. Torsion enables the study of texture formation with strain as well as the exploration of large strains without changing the shape of the samples. The pole figures indicate the preferred alignment of ‹100› with the shear dire...

Full Stress Tensor Determination in A textured Aerospace Aluminium Alloy Plate Using synchrotron X-Ray Diffraction

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

Triaxial strain scanning has been performed on a 7mm thick 7150-aluminium alloy Variable Polarity Plasma Arc (VPPA) weld using synchrotron X-rays. It has been demonstrated that the use of specific advantageous (hkl) peaks that occur in this highly textured aerospace alloy plate permits fast deep measurements in reflection as well as in transmission. The sin⁡2ψ method was also utilised to monitor the variation in deviatoric stress component (σ11−σ33) across the weld in both the test-piece and a comb like reference specimen used to map the changes in stress-free lattice spacings over the weld. The results suggest that microstresses have little effect on macrostress determination, particularly in the Heat Affected Zones (HAZ). Though small in magnitude, the ...

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Use of Synchrotron Diffraction Data for Describing Crystal Structure and Crystallographic Phase Analysis of R-Phase NiTi Shape Memory Alloy

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

The objective of the present article is to use the third generation synchrotron X-ray source at the European Synchrotron Research Facility (ESRF) in Grenoble, which make available X-ray beams of higher energy and much higher intensity than laboratory X-ray sources, for describing crystal structure of the R-phase in 50.75 at.% Ti–47.75 at.% Ni–1.50 at.% Fe ternary alloy. The synchrotron diffraction data of R-phase were analyzed using the Rietveld refinement with GSH description. The results showed that no significant improvement in fit is found when the inversion center is removed from the P3¯ model, suggesting that the space group is indeed P3¯ and not P3. (Source: Texture, Stress, and Microstructure)

Influence of Grain Number on Graphite Quantitative Texture Study

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

The present work is devoted to the study of the grain number influence on the quantitative texture analysis and on the values of averaged elastic properties. Number of grains does not influence mathematical definition of orientation distribution function (ODF) (Bunge, H.J. (1982). Texture Analysis in Material Science. Butterworths, London; Matthies, S., Vinel, G.W. and Helming, K. (1987). Standard Distributions in Texture Analysis. Akademie-Verlag, Berlin.); nevertheless, intuitively clear that, averaging procedure implies a ‘‘large’’ number of grains to make sense. In the present work we applied the already suggested procedure (Lychagina, T.A. and Nikolayev, D.I. (2003). Phys. Stat. Sol. (a), 195(N2), 322–334.) for the case of hexagonal symmetry to evaluate the influence of the ...

Applications on High-Energy X-Rays to Stress Measurements of Thermal Barrier Coatings

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

High-energy X-rays from a synchrotron radiation source, SPring-8, were applied to the stress measurements of thermal barrier coating (TBC). The specimen had a zirconia top coat on a bond coat of NiCoCrAlY sprayed on the substrate of Ni-base super alloys. The stress in the bond coat was measured through the top coat using the diffraction of Ni3Al 311 by high-energy X-rays with an energy of 72 keV. The sin2ψ method was used to determine the stress value. A specially designed furnace with a wide beryllium window was developed to conduct in-situ measurements of the internal stress in the bond coating at the room temperature, 773, 1073, and 1373 K. The internal stress was tensile at the room temperature, and decreased with increasing temperature. At 1073K or higher, the internal stress i...

High-Energy X-Rays: A tool for Advanced Bulk Investigations in Materials Science and Physics

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

The combination of these techniques is a strong issue for the construction and development of future instruments. (Source: Texture, Stress, and Microstructure)

High-Resolution Imaging of Texture and Microstructure by the Moving Detector Method

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

In order to describe texture and microstructure of a polycrystalline material completely, crystal orientation g={ϕ1Φϕ2} must be known in all points x={x1 x2 x3} of the material. This can be achieved by locationresolved diffraction of high-energy, i.e. short-wave, X-rays from synchrotron sources. Highest resolution in the orientation- as well as the location-coordinates can be achieved by three variants of a detector “sweeping” technique in which an area detector is continuously moved during exposure. This technique results in two-dimensionally continuous images which are sections and projections of the six-dimensional “orientation– location” space. Further evaluation of these images depends on whether individual grains are re...

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Hot-Extruded and Cold-Rolled Textures of the Matrix Aluminum in Deformation Processed Two-Phase Nb/Al Metal-Metal Composites

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

In this article, the powder metallurgy technique combined with flat hot-extrusion and cold rolling processes was employed to fabricate 10 and 20vol.%Nb/Al metal–metal composite sheets. The hot-extruded and coldrolled textures of the matrix aluminum in these metal–metal composite sheets were investigated by three dimensional orientation distribution functions (ODFs) analysis. The results show that the extrusion mode and large second phase particulate metal, Nb, have strong influence on the development of the extrusion and cold rolling textures in composites’ matrix. The matrix Al forms β-fiber textures after flat hot extrusion, where the components consist of B′-{011} ‹322›, S′-{124} ‹654› and C′-{113}h332...

Intensity Correction in Texture Measurement of Polycrystalline Thin Films by X-Ray Diffraction

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

The tilting of a specimen may not only result in defocusing effect, but also in a change of irradiated volume during texture measurement for thin films and coatings by using X-ray diffraction. The influence on diffraction intensity has to be considered in order to obtain an accurate result of texture analysis. The effect of irradiated volume can be formulated as a function of the thickness and the linear absorption of a studied film material, the tilt angle of the specimen and the Bragg angle of diffraction, and then eliminated. In view of that the preparation of a randomly oriented specimen would be difficult, a simple and convenient method is hereby proposed to correct the defocusing effect from known data of existing bulk powder specimens with random orientation by interpolation (or ext...

Effect of Gravity on the Kinetics of Consolidation of Powder Bodies

Texture, Stress, and Microstructure — Tue, 03 Nov 2009 16:28:46 +0100

Physical mathematical model of sintering powders is suggested with respect to the influence of gravitation on sintering kinetics. Structure genesis and evolution in sintered glass-based particulate bodies is investigated both in computer simulations and “in situ”. (Source: Texture, Stress, and Microstructure)

Injectable biodegradable hydrogels with tunable mechanical properties for the stimulation of neurogenesic differentiation of human mesenchymal stem cells in 3D culture.

Biomaterials — Tue, 03 Nov 2009 00:00:00 +0100

We report an injectable hydrogel scaffold system with tunable stiffness for controlling the proliferation rate and differentiation of human mesenchymal stem cells (hMSCs) in a three-dimensional (3D) context in normal growth media. The hydrogels composed of gelatin-hydroxyphenylpropionic acid (Gtn-HPA) conjugate were formed using the oxidative coupling of HPA moieties catalyzed by hydrogen peroxide (H(2)O(2)) and horseradish peroxidase (HRP). The stiffness of the hydrogels was readily tuned by varying the H(2)O(2) concentration without changing the concentration of polymer precursor. We found that the hydrogel stiffness strongly affected the cell proliferation rates. The rate of hMSC proliferation increased with the decrease in the stiffness of the hydrogel. Also, the neurogenesis of hMSCs ...

Promotion of osteoblast proliferation on complex coacervation-based hyaluronic acid - recombinant mussel adhesive protein coatings on titanium.

Biomaterials — Tue, 03 Nov 2009 00:00:00 +0100

Authors: Hwang DS, Waite JH, Tirrell M Many biological polyelectrolytes are capable of undergoing a fluid-fluid phase separation known as complex coacervation. Coacervates were prepared using hyaluronic acid (HA) and a recombinant fusion protein consisting of mussel adhesive motifs and the RGD peptide (fp-151-RGD). The low interfacial energy of the coacervate was exploited to coat titanium (Ti), a metal widely used in implant materials. The coacervate effectively distributed both HA and fp-151-RGD over the Ti surfaces and enhanced osteoblast proliferation. Approximately half of total fp-151-RGD and HA in the solution transferred to the titanium surface within 2h. Titanium coated with coacervates having high residual negative surface charge showed the highest cell proliferation of preos...

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Surface-energy dependent contact activation of blood factor XII.

Biomaterials — Tue, 03 Nov 2009 00:00:00 +0100

Authors: Golas A, Parhi P, Dimachkie ZO, Siedlecki CA, Vogler EA Contact activation of blood factor XII (FXII, Hageman factor) in neat-buffer solution exhibits a parabolic profile when scaled as a function of silanized-glass-particle activator surface energy (measured as advancing water adhesion tension tau(a)(o)=gamma(lv)(o)costheta in dyne/cm, where gamma(lv)(o) is water interfacial tension in dyne/cm and theta is the advancing contact angle). Nearly equal activation is observed at the extremes of activator water-wetting properties -36<tau(a)(o)<72dyne/cm (0 degrees </=theta<120 degrees ), falling sharply through a broad minimum within the 20<tau(a)(o)<40dyne/cm (55 degrees <theta<75 degrees ) range over which activation yield (putatively FXIIa) rises just abo...

The contribution of plasmid design and release to in vivo gene expression following delivery from cationic polymer modified scaffolds.

Biomaterials — Tue, 03 Nov 2009 00:00:00 +0100

In this report, we investigate the relationship between plasmid release kinetics and the extent and duration of transgene expression. Scaffolds were fabricated from polymer microspheres modified with cationic polymers (polyethylenimine, poly(l-lysine), poly(allylamine hydrochloride), polydiallyldimethylammonium) or polydopamine (PD), with PD enhancing incorporation and slowing release. In vivo implantation of scaffolds into the peritoneal fat pad had no significant changes in the level and duration of transgene expression between PD and unmodified scaffolds. Control studies with plasmid dried onto scaffolds, which exhibited a rapid release, and scaffolds with extended leaching to reduce initial quantities released had similar levels and duration of expression. Changing the plasmid design, ...

Editors for Acta Materialia

Acta Materialia — Mon, 02 Nov 2009 16:47:55 +0100

(Source: Acta Materialia)

The use of RGDGWK-lipopeptide to selectively deliver genes to mouse tumor vasculature and its complexation with p53 to inhibit tumor growth.

Biomaterials — Mon, 02 Nov 2009 00:00:00 +0100

Authors: Samanta S, Sistla R, Chaudhuri A In vivo selection of phage display libraries have been exploited successfully in the past to isolate various high affinity conformationally strained cyclic peptide ligands (CX(5-7)C, peptides flanked by a cysteine residue on each side) for integrin receptors capable of selectively homing to tumor vasculatures. Previously, such phase display library studies have shown that integrin alpha5beta1 binds with high affinity to cyclic peptides containing CRGDGWC motif. Herein we show that a lipopeptide with just the RGDGW motif (without the flanking cysteine groups) covalently attached to the lysine residue of a monolysinylated cationic amphiphile (RGDGWK-lipopeptide 1) delivers genes to cultured cells preferably via alpha5beta1 integrins. Importantly,...

Nanoparticles functionalised with recombinant single chain Fv antibody fragments (scFv) for the magnetic resonance imaging of cancer cells.

Biomaterials — Mon, 02 Nov 2009 00:00:00 +0100

Authors: Vigor KL, Kyrtatos PG, Minogue S, Al-Jamal KT, Kogelberg H, Tolner B, Kostarelos K, Begent RH, Pankhurst QA, Lythgoe MF, Chester KA Superparamagnetic iron oxide nanoparticles (SPIONs) can substantially improve the sensitivity of magnetic resonance imaging (MRI). We propose that SPIONs could be used to target and image cancer cells if functionalised with recombinant single chain Fv antibody fragments (scFv). We tested our hypothesis by generating antibody-functionalised (abf) SPIONs using a scFv specific for carcinoembryonic antigen (CEA), an oncofoetal cell surface protein. SPIONs of different hydrodynamic diameter and surface chemistry were investigated and targeting was confirmed by ELISA, cellular iron uptake, confocal laser scanning microscopy (CLSM) and MRI. Results demon...

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The delivery of superoxide dismutase encapsulated in polyketal microparticles to rat myocardium and protection from myocardial ischemia-reperfusion injury.

Biomaterials — Mon, 02 Nov 2009 00:00:00 +0100

Authors: Seshadri G, Sy JC, Brown M, Dikalov S, Yang SC, Murthy N, Davis ME Oxidative stress is increased in the myocardium following infarction and plays a significant role in death of cardiac myocytes, leading to cardiac dysfunction. Levels of the endogenous antioxidant Cu/Zn-superoxide dismutase (SOD1) decrease following myocardial infarction. While SOD1 gene therapy studies show promise, trials with SOD1 protein have had little success due to poor pharmacokinetics and thus new delivery vehicles are needed. In this work, polyketal particles, a recently developed delivery vehicle, were used to make SOD1-encapsulated-microparticles (PKSOD). Our studies with cultured macrophages demonstrated that PKSOD treatment scavenges both intracellular and extracellular superoxide, suggesting effi...

Engineering a scaffold-free 3D tumor model for in vitro drug penetration studies.

Biomaterials — Mon, 02 Nov 2009 00:00:00 +0100

Authors: Ong SM, Zhao Z, Arooz T, Zhao D, Zhang S, Du T, Wasser M, van Noort D, Yu H Three-dimensional (3D) in vitro cultures are recognized for recapitulating the physiological microenvironment and exhibiting high concordance with in vivo conditions. In cancer research, the multi-cellular tumor spheroid (MCTS) model is an established 3D cancer model that exhibits microenvironmental heterogeneity close to that of tumors in vivo. However, the established process of MCTS formation is time-consuming and often uncontrolled. Here, we report a method for engineering MCTS using a transient inter-cellular linker which facilitates cell-cell interaction. Using C3A cells (a hepatocellular carcinoma cell line) as a model, we formed linker-engineered spheroids which grew to a diameter of 250mum in ...

Self-Assembly of phospholipid-analogous hyperbranched polymers nanomicelles for drug delivery.

Biomaterials — Sat, 31 Oct 2009 00:00:00 +0100

Authors: Liu J, Pang Y, Huang W, Zhu X, Zhou Y, Yan D A drug nanocarrier has been constructed through self-assembly of phospholipid analogous hyperbranched polymers (HPHEEP-alkyls) which contain a polar hyperbranched polyphosphate headgroup and many aliphatic tails. HPHEEP-alkyls were synthesized by self-condensing ring-opening polymerization of 2-(2-hydroxyethoxy)ethoxy-2-oxo-1,3,2-dioxaphospholane and then capped with palmitoyl chloride. Benefiting from the amphiphilic structure with the hydrophilic core and many hydrophobic tails, HPHEEP-alkyls were able to self-assemble into nanomicelles in aqueous media. Importantly, the size of the nanomicelles could be controlled conveniently from 98 to 215nm by adjusting the capped fraction of the hydroxyl groups with hydrophobic palmityls. The...

Partly PEGylated polyamidoamine dendrimer for tumor-selective targeting of doxorubicin: The effects of PEGylation degree and drug conjugation style.

Biomaterials — Sat, 31 Oct 2009 00:00:00 +0100

Authors: Zhu S, Hong M, Tang G, Qian L, Lin J, Jiang Y, Pei Y Partly PEGylated polyamidoamine (PAMAM) dendrimers were used as the carrier for tumor-selective targeting of the anticancer drug doxorubicin (DOX). Acid-sensitive cis-aconityl linkage or acid-insensitive succinic linkage was introduced between DOX and polymeric carriers to produce PPCD or PPSD conjugates, respectively. DOX release from PPCD conjugates followed an acid-triggered manner and increased with increasing PEGylation degree. In vitro cytotoxicity of PPCD conjugates against murine B16 melanoma cells increased with, while cellular uptake decreased with increasing PEGylation degree. PPSD conjugates released negligible drug at any tested pH condition and were less cytotoxic. Confocal laser scanning microscopy confirmed t...

Density functional theory calculations and molecular dynamics simulations of the adsorption of biomolecules on graphene surfaces.

Biomaterials — Fri, 30 Oct 2009 00:00:00 +0100

Authors: Qin W, Li X, Bian WW, Fan XJ, Qi JY There is increasing attention in the unique biological and medical properties of graphene, and it is expected that biomaterials incorporating graphene will be developed for the graphene-based drug delivery systems and biomedical devices. Despite the importance of biomolecules-graphene interactions, a detailed understanding of the adsorption mechanism and features of biomolecules onto the surfaces of graphene is lacking. To address this, we have performed density functional theory (DFT) and molecular dynamics (MD) methods exploring the adsorption geometries, adsorption energies, electronic band structures, adsorption isotherms, and adsorption dynamics of l-leucine (model biomolecule)/graphene composite system. DFT calculations confirmed the e...

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The performance of a fly-larva shell-derived chitosan sponge as an absorbable surgical hemostatic agent.

Biomaterials — Fri, 30 Oct 2009 00:00:00 +0100

Authors: Gu R, Sun W, Zhou H, Wu Z, Meng Z, Zhu X, Tang Q, Dong J, Dou G Chitosan is a versatile biomaterial lately used as a new generation of local hemostatic agent approved to date for external use only. Here we introduced a fly-larva shell-derived chitosan sponge (CS) and its feasibility for internal use as an absorbable surgical hemostatic agent was evaluated in a rat hepatic hemorrhage model. CS was a better implantable hemostatic material than gelatin sponge (GS) or oxidized cellulose (OC) in both the acute and chronic bleeding models. The better efficacy of CS may be due to its greater ability to enhance platelet activation, erythrocyte aggregation and morphological alteration, and thrombin generation at sites it is applied than GS or OC. Moreover, preliminary safety evaluation...

The effect of PEGylation of mesoporous silica nanoparticles on nonspecific binding of serum proteins and cellular responses.

Biomaterials — Fri, 30 Oct 2009 00:00:00 +0100

Authors: He Q, Zhang J, Shi J, Zhu Z, Zhang L, Bu W, Guo L, Chen Y Highly ordered MCM-41-type mesoporous silica nanoparticles (MSNs) with particle sizes of 150 +/- 20 nm were prepared and PEGylated by covalently grafting PEGxk chains of different molecular weights (x = 4, 6, 10, 20) and chain densities (0.05 wt%-3.75 wt%) on the outer surface. The influence of molecular weights and chain densities of PEGxk on the nonspecific binding of PEGylated MSNs to human serum protein (HSA) was investigated. The results revealed that the optimal molecular weights should be not less than 10k, and the corresponding optimal chain densities for PEG10k-MSNs and PEG20k-MSNs were 0.75 wt% and 0.075 wt%, respectively, and the resultant minimum HSA adsorbance (2.5%) on PEGxk-MSNs was far less than that on ...

The repair of large segmental bone defects in the rabbit with vascularized tissue engineered bone.

Biomaterials — Fri, 30 Oct 2009 00:00:00 +0100

We report herein the construction of a vascularized tissue engineered bone with mesenchymal stem cells (MSCs) and MSC-derived endothelial cells (ECs) co-cultured in porous beta-tricalcium phosphate ceramic (beta-TCP) to repair 1.5-cm ulnar defects in the rabbit. Examination by X-ray and single photon emission computed tomography (SPECT), histologic analysis, and biomechanical tests were used to evaluate repair and the vascularization of the implants. The results showed that by co-seeding MSCs and MSC-derived ECs, the resulting vascularization was able to promote osteogenesis and improve mechanical properties. The rabbits treated with vascularized tissue engineered bone exhibited far more extensive osteogenesis and good vascularization. Therefore, we suggest that the vascularized tissue eng...

Surface characteristics and in vitro biocompatibility of titanium anodized in a phosphoric acid solution at different voltages

Biomedical Materials — Fri, 30 Oct 2009 00:00:00 +0100

Author(s): Z X Chen, Y Takao, W X Wang, T Matsubara and L M RenAffiliation(s): Research Institute for Applied Mechanics, Kyushu University, Kasuga-koen 6-1, Kasuga, Fukuoka 816-8580, Japan (Source: Biomedical Materials)

The Journal of Pain — Thu, 29 Oct 2009 16:25:19 +0100

(Source: The Journal of Pain)

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Editorial Board

The Journal of Pain — Thu, 29 Oct 2009 16:25:19 +0100

(Source: The Journal of Pain)

Masthead

The Journal of Pain — Thu, 29 Oct 2009 16:25:19 +0100

(Source: The Journal of Pain)

Role of NFκB in an Animal Model of Complex Regional Pain Syndrome–type I (CRPS-I)

The Journal of Pain — Thu, 29 Oct 2009 16:25:19 +0100

Abstract: NFκB is involved in several pathogenic mechanisms that are believed to underlie the complex regional pain syndrome (CRPS), including ischemia, inflammation and sensitization. Chronic postischemia pain (CPIP) has been developed as an animal model that mimics the symptoms of CRPS-I. The possible involvement of NFκB in CRPS-I was studied using CPIP rats. Under sodium pentobarbital anesthesia, a tourniquet was placed around the rat left ankle joint, producing 3 hours of ischemia, followed by rapid reperfusion (IR injury). NFκB was measured in nuclear extracts of muscle and spinal cord tissue using ELISA. Moreover, the anti-allodynic (mechanical and cold) effect was tested for systemic, intrathecal, or intraplantar treatment with the NFκB inhibitor pyrrolidine dithiocarbamate (PDT...

How Neuroimaging Studies Have Challenged Us to Rethink: Is Chronic Pain a Disease?

The Journal of Pain — Thu, 29 Oct 2009 16:25:18 +0100

Abstract: In this review, we present data from functional, structural, and molecular imaging studies in patients and animals supporting the notion that it might be time to reconsider chronic pain as a disease. Across a range of chronic pain conditions, similar observations have been made regarding changes in structure and function within the brains of patients. We discuss these observations within the framework of the current definition of a disease.Perspective: Neuroimaging studies have made a significant scientific impact in the study of pain. Knowledge of nociceptive processing in the noninjured and injured central nervous system has grown considerably over the past 2 decades. This review examines the information from these functional, structural, and molecular studies within the framew...

Nanotopography-induced changes in focal adhesions, cytoskeletal organization, and mechanical properties of human mesenchymal stem cells.

Biomaterials — Thu, 29 Oct 2009 00:00:00 +0100

Authors: Yim EK, Darling EM, Kulangara K, Guilak F, Leong KW The growth of stem cells can be modulated by physical factors such as extracellular matrix nanotopography. We hypothesize that nanotopography modulates cell behavior by changing the integrin clustering and focal adhesion (FA) assembly, leading to changes in cytoskeletal organization and cell mechanical properties. Human mesenchymal stem cells (hMSCs) cultured on 350nm gratings of tissue-culture polystyrene (TCPS) and polydimethylsiloxane (PDMS) showed decreased expression of integrin subunits alpha2, alpha6, alphaV, beta2, beta3 and beta4 compared to the unpatterned controls. On gratings, the elongated hMSCs exhibited an aligned actin cytoskeleton, while on unpatterned controls, spreading cells showed a random but denser acti...

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Ultrapure chitosan oligomers as carriers for corneal gene transfer.

Biomaterials — Thu, 29 Oct 2009 00:00:00 +0100

This study lays the foundation for evaluating oligomeric chitosan-DNA nanoparticles as pharmaceuticals for corneal gene therapy, a promising approach for the treatment of acquired and inherited corneal diseases that otherwise lead to blindness. Oligomeric chitosan-DNA nanoparticles can also be evaluated for the treatment of ocular diseases outside of the cornea, and for various additional gene therapy applications. PMID: 19879644 [PubMed - as supplied by publisher] (Source: Biomaterials)

The relationship between the nanostructure of titanium surfaces and bacterial attachment.

Biomaterials — Thu, 29 Oct 2009 00:00:00 +0100

This study examined the adhesion of Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa on conventional Ti, nanorough Ti produced by electron beam evaporation, and nanotubular and nanotextured Ti produced by two different anodization processes. This study found that compared to conventional (nano-smooth) Ti, the nanorough Ti surfaces produced by electron beam evaporation decreased the adherence of all of the aforementioned bacteria the most. The conventional and nanorough Ti surfaces were found to have crystalline TiO(2) while the nanotubular and nanotextured Ti surfaces were found to be amorphous. The surface chemistries were similar for the conventional and nanorough Ti while the anodized Ti surfaces contained fluorine. Therefore, the results of this study in vi...

The role of antibody synergy and membrane fluidity in the vascular targeting of immunoliposomes.

Biomaterials — Thu, 29 Oct 2009 00:00:00 +0100

We report that cellular binding of DOPC immunoliposomes by ECs is maximal at an equimolar ratio of aICAM:aELAM whereas DPPC immunoliposomes showed no ratio dependence and binding was reduced by more than 2-fold. SMCs, which do not express ELAM, show a dependence on aICAM surface density. These results suggest that antibody mobility and molar ratio play a key role in increasing receptor-mediated cell targeting. PMID: 19879646 [PubMed - as supplied by publisher] (Source: Biomaterials)

Cationic and thermosensitive protamine conjugated gels for enhancing sustained human growth hormone delivery.

Biomaterials — Thu, 29 Oct 2009 00:00:00 +0100

Authors: Park MR, Chun C, Ahn SW, Ki MH, Cho CS, Song SC Thermosensitive and cationic poly(organophosphazenes) were designed and synthesized for the sustained delivery of human growth hormone (hGH) charged negatively at the physiological conditions to enhance greatly patient convenience and to improve efficacy and stability. Protamine for a complex formation with hGH was chosen and conjugated to carboxylic acid-terminated poly(organophosphazenes) by a covalent amide linkage. The aqueous solution of the cationic polymer conjugates formed a gel at 37 degrees C regardless of hGH presence. When the conjugate solution was mixed with hGH solution, a complex was formed and free hGH could be released from the complex. In the in vitro and in vivo release studies of hGH/polymer-protamine conjuga...

Movement of polymer microcarriers using a biomolecular motor.

Biomaterials — Thu, 29 Oct 2009 00:00:00 +0100

Authors: Song W, Möhwald H, Li J This work enables polymer microcarriers to be transported on a motor protein coated substrate. The size of microencapsulation system- layered polymer capsules could be controlled through changing heating time during post-treatment. In this active biomimetic system, the microtubules act as shuttles that transport the attached polymer microcarriers. The velocity of the motility does not depend on size of the capsules but the fraction of mobile capsules depends on capsule size and biotinylation proportion of microtubule. The microtubule could also propel dextran-filled capsules to transport the internal components on the activated surface. The study integrates the artificial materials into kinesin-microtubule system and provides a potential use for st...

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The biocompatibility of materials used in printed circuit board technologies with respect to primary neuronal and K562 cells.

Biomaterials — Wed, 28 Oct 2009 00:00:00 +0100

In this study, we analyzed the in-vitro compatibility of a large set of materials and surface treatments used for LOAC development and evaluation with quasi-standard PCB processes. Biocompatibility was analyzed on hippocampal primary cells (a model of attached cell cultures), in comparison with the reference K562 cell line (a model of cells growing in suspension). We demonstrate here that some of the materials under study alter survival, organization, morphology and adhesion capacity of hippocampal cells, and inhibit growth and differentiation of K562 cells. Nonetheless, a subset of the materials tested did not negatively affect these functions, thus demonstrating that PCB technology, with some limitations, is suitable for the realization of LOAC devices well compatible at least with these...

Size control of magnetic carbon nanoparticles for drug delivery.

Biomaterials — Wed, 28 Oct 2009 00:00:00 +0100

Authors: Oh WK, Yoon H, Jang J Carbonized polypyrrole nanoparticles with controlled diameters were readily fabricated by the pyrolysis of polypyrrole nanoparticles. The carbonized polypyrrole nanoparticles showed narrow size distribution, large micropore volume, and high surface area. Magnetic phases were introduced into the carbon nanoparticles during the pyrolysis without sophisticated process, which resulted in useful magnetic properties for selective nanoparticle separation. Field emission scanning electron microscopy, Raman spectrometer, N(2) adsorption/desorption, X-ray diffraction, and superconducting interference device were employed for characterizing the carbonized polypyrrole nanoparticles. Hydrophobic guest molecules were incorporated into the carbonized polypyrrole nanopar...

Structure-activity relationships of cationic shell-crosslinked knedel-like nanoparticles: Shell composition and transfection efficiency/cytotoxicity.

Biomaterials — Wed, 28 Oct 2009 00:00:00 +0100

Authors: Zhang K, Fang H, Wang Z, Li Z, Taylor JS, Wooley KL Cationic nanoparticles are a promising class of transfection agents for oligonucleotide and gene delivery, but vary greatly in their effectiveness and cytotoxicity. Recently, we developed a new class of cationic transfection agents based on cationic shell-crosslinked knedel-like nanoparticles (cSCKs) that efficiently transfect mammalian cells with both oligonucleotides and plasmid DNA. In an effort to further improve transfection efficiency without increasing cytotoxicity, we examined the effects of the composition of primary amine (pa), tertiary amine (ta) and carboxylic acid (ca) groups in the shell of these nanoparticles. A series of discrete complexes of the cSCKs with plasmid DNA (pDNA) or phosphorothioate 2'-OMe oliogon...

The in vivo performance of magnetic particle-loaded injectable, in situ gelling, carriers for the delivery of local hyperthermia.

Biomaterials — Wed, 28 Oct 2009 00:00:00 +0100

Authors: Le Renard PE, Jordan O, Faes A, Petri-Fink A, Hofmann H, Rüfenacht D, Bosman F, Buchegger F, Doelker E We investigated the use of in situ implant formation that incorporates superparamagnetic iron oxide nanoparticles (SPIONs) as a form of minimally invasive treatment of cancer lesions by magnetically induced local hyperthermia. We developed injectable formulations that form gels entrapping magnetic particles into a tumor. We used SPIONs embedded in silica microparticles to favor syringeability and incorporated the highest proportion possible to allow large heating capacities. Hydrogel, single-solvent organogel and cosolvent (low-toxicity hydrophilic solvent) organogel formulations were injected into human cancer tumors xenografted in mice. The thermoreversible hydrogels (...

Polyethylenimine-PEG coated albumin nanoparticles for BMP-2 delivery.

Biomaterials — Wed, 28 Oct 2009 00:00:00 +0100

In this study, we report a nanoparticulate (NP) system for BMP-2 delivery based on bovine serum albumin (BSA) NPs stabilized with a poly(ethylene glycol) modified polyethylenimine (PEI-PEG) coating. PEI-PEG with different PEG substitutions were synthesized, and the cell viability assay showed PEG substitution greatly reduced the cytotoxicity of the native PEI. Furthermore, PEI-PEG coated BSA NPs demonstrated smaller size and decreased zeta potential compared to PEI-coated NPs. The bioactivity of the encapsulated BMP-2 and the toxicity of PEI-PEG coated NPs were examined by the alkaline phosphatase (ALP) induction assay and the MTT assay, respectively, using human C2C12 cells. The results indicated that BMP-2 remained bioactive in NPs and PEI-PEG coating was advantageous in reducing the NP ...

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The mechanically enhanced phase separation of sprayed polyurethane scaffolds and their effect on the alignment of fibroblasts.

Biomaterials — Wed, 28 Oct 2009 00:00:00 +0100

Authors: Kennedy JP, McCandless SP, Lasher RA, Hitchcock RW This paper reports a method to fabricate anisotropic scaffolds of tunable porosity and mechanical properties. Scaffolds were fabricated using a computer controlled sprayed phase separation technique. Following fabrication, the sheets were elongated 0, 35 or 70% of their original length to induce varying degrees of scaffold alignment and anisotropy. The nonsolvent used in the phase separation was shown to affect porosity and the elastic modulus. Mouse embryo NIH-3T3 fibroblasts were cultured on the scaffolds to investigate cell response to the anisotropy of the scaffold. A 2D FFT method was used to quantify cellular alignment. Cells were shown to align themselves with the scaffold. This sheet-like scaffold material can be used ...

Hydrodynamic spinning of hydrogel fibers.

Biomaterials — Wed, 28 Oct 2009 00:00:00 +0100

Authors: Hu M, Deng R, Schumacher KM, Kurisawa M, Ye H, Purnamawati K, Ying JY Hydrogel scaffolds are highly hydrated polymer networks that allow cells to adhere, proliferate and differentiate in the treatment of diseased or injured tissues and organs. Using hydrodynamic shaping and in situ cross-linking of hydrogel precursors, we have developed a highly efficient "hydrodynamic spinning" approach for synthesizing hydrogel fibers of different diameters in a multiphase coaxial flow. A triple-orifice spinneret has been created, and three different types of hydrogel precursors have been examined. Without changing the spinning head, hollow and solid hydrogel fibers with different diameters have been spun by simply manipulating the ratio of input flow rates. Together with the ability of simu...

Fatigue-life assessment and validation techniques for metallic vascular implants.

Biomaterials — Tue, 27 Oct 2009 00:00:00 +0100

Authors: James BA, Sire RA Vascular implants, such as cardiac valve prostheses, stents, and other devices are often subjected to complex loading conditions in vivo, which can include pulsatile pressure cycling, bending, torsion, tension, and compression, among others. At an average of 72 heartbeats per minute, pulsatile loading alone produces approximately 40-million cycles per year. With design lives of 10-15 years, fatigue performance assessment and validation of these devices are critical for the designer, as mechanical failure can have serious consequences. Historically, various fatigue life assessment approaches have been used to validate endovascular device fatigue performance, including durability testing, stress/strain-life analysis, and damage tolerance-based analysis. This pa...

Structural–acoustic modal analysis of cylindrical shells: application to MRI scanner systems

Magnetic Resonance Materials in Physics, Biology and Medicine — Mon, 26 Oct 2009 18:00:23 +0100

Conclusion These methods are effective for coupled and uncoupled modal analysis of MRI scanner systems and can be used for quiet MRI design or sound absorber design for existing MRI systems. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-009-0185-zAuthors Gemin Li, Queen’s University Department of Mechanical Engineering McLaughlin Hall Kingston ON K7L 3N6 CanadaChris K. Mechefske, Queen’s University Department of Mechanical Engineering McLaughlin Hall Kingston ON K7L 3N6 Canada Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 (Source: Magnetic Resonance Materials in Physics, Biology and Medicine)

Editors for Scripta Materialia

Scripta Materialia — Mon, 26 Oct 2009 16:59:51 +0100

(Source: Scripta Materialia)

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Influence of the shape of the layers in photo-cured dental restorations on the shrinkage stress peaks—FEM study

Dental Materials — Mon, 26 Oct 2009 16:59:45 +0100

Abstract: Objective: The aim of the paper is to analyse an influence of the shape of the layers in photo-cured dental restorations of Class I on distribution of shrinkage stresses along the tooth-restoration interface. The study is a continuation of the previous considerations (Kowalczyk and Gambin (2008) ), where techniques, which reduce stress concentration at the top of the tooth-restoration interface, were considered. The analysis leads to proposition of new layer forming techniques, which diminish the stress peaks at the interface and prevent the crack propagation process.Methods: To find the stress distributions in the dental restoration layers and the tooth tissues the finite element method implemented in the ABAQUS (Simulia, Providence, USA) software is used. For Class I restoratio...

Effect of resin-composite filler particle size and shape on shrinkage–strain

Dental Materials — Mon, 26 Oct 2009 16:59:45 +0100

Abstract: Objectives: The aim of this study was to investigate the effect of variations in filler particle size and shape on the polymerization shrinkage–strain kinetics of resin-composites.Methods: A model series of 12 VLC resin-composites were studied. The particulate dispersed phase volume fraction was 56.7%: these filler particles were systematically graded in size, and further were either spherical or irregular. The bonded disk method was used to determine shrinkage–strain kinetics. Displacement was recorded following 40s irradiation (600mW/cm2) at 23°C (n=3). All data were captured for 60min and the final shrinkage–strain calculated.Results: For materials with spherical filler, shrinkage–strain was 2.66% (SD 0.18) for those with irregular filler it was 2.89% (SD 0.11). These...

Photobleaching of camphorquinone during polymerization of dimethacrylate-based resins

Dental Materials — Mon, 26 Oct 2009 16:59:44 +0100

Abstract: Objective: The aim of this study was to compare the photobleaching rate of CQ in different dental resins.Methods: The photodecomposition rate of CQ/amine system in bis-GMA/TEGDMA, bis-EMA and UDMA polymerizing monomers was evaluated at different light intensities. The photobleaching of the CQ was studied by monitoring the decrease in light absorption as a function of continuous irradiation time. The absorption changes were assessed by recording the transmitted light that passed through samples of monomers containing CQ/amine.Results: Complete photobleaching of CQ was observed in all the monomer tested and the rate constant for the photobleaching was proportional to the radiation intensity. Hydrogen abstraction from amines by the excited CQ state via electron transfer and direct h...

Characterization of mouthguard materials: Thermal properties of commercialized products

Dental Materials — Mon, 26 Oct 2009 16:59:44 +0100

Abstract: Objectives: Several mechanisms have been purported to describe how mouthguards protect the orofacial complex against injury. As the properties needed for these mechanisms to be effective are temperature and frequency dependent, the specific aim of this study was to provide a comprehensive thermal characterization of commercial mouthguard materials.Methods: Five commercially representative thermoplastic mouthguard materials (Essix™ Resin, Erkoflex™, Proform™-regular, Proform™-laminate, and Polyshok™) were tested. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques were implemented to measure thermal transitions and mechanical properties. Measurements were conducted three times per sample. One-way ANOVA and one-sample t-tests were used...

Effect of filler particle size and morphology on force/work parameters for stickiness of unset resin-composites

Dental Materials — Mon, 26 Oct 2009 16:59:44 +0100

Conclusion: Filler particle size and morphology influences Fmax and Ws of uncured resin-composite which partly express the handling behaviors of resin-composites. (Source: Dental Materials)

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Influence of curing protocol on selected properties of light-curing polymers: Degree of conversion, volume contraction, elastic modulus, and glass transition temperature

Dental Materials — Mon, 26 Oct 2009 16:59:44 +0100

Abstract: Objectives: The purpose of this study was to investigate the effect of light-curing protocol on degree of conversion (DC), volume contraction (C), elastic modulus (E), and glass transition temperature (Tg) as measured on a model polymer. It was a further aim to correlate the measured values with each other.Methods: Different light-curing protocols were used in order to investigate the influence of energy density (ED), power density (PD), and mode of cure on the properties. The modes of cure were continuous, pulse-delay, and stepped irradiation. DC was measured by Raman micro-spectroscopy. C was determined by pycnometry and a density column. E was measured by a dynamic mechanical analyzer (DMA), and Tg was measured by differential scanning calorimetry (DSC). Data were submitted to...

Water sorption and dynamic mechanical properties of dentin adhesives with a urethane-based multifunctional methacrylate monomer

Dental Materials — Mon, 26 Oct 2009 16:59:44 +0100

The objective of this work was to further investigate the performance of dentin adhesives containing a new monomer, with particular emphasis on the water sorption and viscoelastic behavior of the crosslinked networks.Materials and methods: Dentin adhesives contained 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]-propane (BisGMA), 2-hydroxyethyl methacrylate (HEMA), and a new multifunctional methacrylate with urethane-linked groups-1,1,1-tri-[4-(methacryloxyethylaminocarbonyloxy)-phenyl]ethane (MPE) and were photo-polymerized in the presence or absence of water. Adhesives were characterized with regard to degree of conversion (DC), viscosity, water sorption/solubility, and dynamic mechanical analysis (DMA) and compared with BisGMA/HEMA controls.Results: The experimental adhesives exhib...

Effect of resin matrix composition on the translucency of experimental dental composite resins

Dental Materials — Mon, 26 Oct 2009 16:59:44 +0100

Abstract: Objectives: The purpose of this study was to investigate the effect of the resin matrix composition on the translucency of experimental dental composite resins.Methods: Three types of unfilled resin matrices (TEGDMA-, UDMA- and BisGMA-based) were formulated and light cured. In addition, six different experimental dental composite resins with constant filler loading but varying in the type of monomer and the content of BisGMA were fabricated. Discs of each test material with 15.5mm diameter and 1.0mm thickness were prepared (N=3) and light cured. Total and diffuse transmittance values for each sample were measured using a UV/VIS spectrophotometer with the range of readings from 380 to 700nm. Difference in color was measured using the CIE Lab system.Results: Statistical analysis by...

Non-irradiated campherquinone induces DNA damage in human gingival fibroblasts

Dental Materials — Mon, 26 Oct 2009 16:59:43 +0100

Abstract: Objectives: Camphorquinone (CQ) is cytotoxic in cell cultures. The mechanism of this toxic action, however, is not yet clearly understood. Aim of this investigation was to analyze the effects of non-irradiated CQ on intracellular formation of reactive oxygen species (ROS), intracellular glutathione (GSH) content, and the integrity of DNA in cultured primary human gingival fibroblasts (HGF).Methods: Cells were exposed to CQ at concentrations ranging between 0.05mM and 2.5mM. Intracellular levels of ROS were detected by the fluorescent probe 2′,7′-dichlorofluorescein diacetate (DCFH-DA) and GSH was determined by the fluorescent probe monobromobimane (MBBr). Genotoxicity was measured quantitatively by the alkaline comet assay. The cytotoxic effects of CQ were investigated by mea...

In vitro cytotoxicity evaluation of elemental ions released from different prosthodontic materials

Dental Materials — Mon, 26 Oct 2009 16:59:43 +0100

This study investigated the cytotoxicity of elemental ions contained in four fixed prosthodontic materials (gold, nickel–chromium, stainless-steel alloys and CAD–CAM ceramics).Materials and methods: According to the determination of elements released from prosthodontic materials by using inductively coupled plasma mass spectroscopy, similar amounts of elements Pd, Ag, Zn, Cu, Ni, Cr, Mo, Be, Fe, Al, and K were prepared as salt solutions. Wells with a tenfold higher concentration of the tested elements were used as positive controls, while a well without any tested element was used as a negative control. These salt solutions were tested for cytotoxicity by culturing mouse L-929 fibroblasts in the salt solutions for a 7-day period of incubation. Then, the percentage of viable cells for e...

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Influence of contamination and cleaning on bond strength to modified zirconia

Dental Materials — Mon, 26 Oct 2009 16:59:43 +0100

Abstract: Objective: To evaluate the influence of contamination and cleaning procedures on shear bond strength (SBS) to modified zirconia surfaces.Methods: One hundred zirconium-oxide ceramic disks fabricated with a rough modified surface (Nobel Bond), which allows more micromechanical interlocking for adhesive cementation, were divided into five groups. Groups were contaminated with organic (OC; human blood and saliva) and/or inorganic contaminants (IC; type IV dental stone). For cleaning, modified surfaces were etched with phosphoric acid for 1min (PA) or fired in a ceramic furnace up to 910°C and cleaned in an ultrasonic bath in ethanol (FU). Following combinations of contamination and cleaning protocols were chosen: group 1: OC-PA; group 2: IC-FU; group 3: OC+IC-PA+FU; group 4: OC+IC-...

N-Acetyl cysteine (NAC) inhibits proliferation, collagen gene transcription, and redox stress in rat palatal mucosal cells

Dental Materials — Mon, 26 Oct 2009 16:59:43 +0100

This study provides a basis to explore NAC-containing biomaterials that are functionalized to control oral soft tissue growth and function without cytotoxicity. (Source: Dental Materials)

Fatigue limits of enamel bonds with moist and dry techniques

Dental Materials — Mon, 26 Oct 2009 16:59:43 +0100

Abstract: Objective: Shear fatigue limit (SFL) testing, coupled with shear bond strength (SBS) measurements can provide valuable information regarding the ability of adhesive systems to bond to mineralized tooth structures. The clinical technique for enamel bonding with adhesive resins has shifted from bonding to a thoroughly dried acid conditioned surface to a moist surface to facilitate dentin bonding. The purpose of this study was to compare the performance of ethanol-containing etch-and-rinse adhesive (ERA) systems on moist and dry enamel by determining the resin composite to enamel SBS and SFL, and examining the relationship of SBS and SFL.Methods: Twelve specimens each were used to determine 24-h resin composite (Z100 – 3M ESPE) to enamel SBS to moist and dry surfaces with two ERA ...

Evaluation of bacteria-induced enamel demineralization using optical profilometry

Dental Materials — Mon, 26 Oct 2009 16:59:42 +0100

Abstract: Objectives: Streptococcus mutans is considered a major causative of tooth decay due to its ability to rapidly metabolize carbohydrates such as sucrose. One prominent excreted end product of sucrose metabolism is lactic acid. Lactic acid causes a decrease in the pH of the oral environment with subsequent demineralization of the tooth enamel. Biologically relevant bacteria-induced enamel demineralization was studied.Methods: Optical profiling was used to measure tooth enamel decay with vertical resolution under one nanometer and lateral features with optical resolution as a result of S. mutans biofilm exposure. Comparison measurements were made using AFM.Results: After 72h of biofilm exposure the enamel displayed an 8-fold increase in the observed roughness average (Ra), as calcula...

Setting characteristics and cavity adaptation of low-shrinking resin composites

Dental Materials — Mon, 26 Oct 2009 16:59:42 +0100

Abstract: Objectives: The aim of this study was to evaluate the setting characteristics of low-shrinking resin composites and examine the possible interactions with curing efficiency and marginal adaptation in dentin cavities.Methods: The materials tested were Ceram X Mono/CM, Premise/PR, Clearfil Majesty/CM, ELS/EL, and Filtek Silorane/FS. Polymerization shrinkage strain (%S), strain rate (%Sr) and time at maximum strain rate (tmax) were measured using the bonded disk method. Curing efficiency was measured on the top and bottom surfaces of composites with ATR-FTIR spectroscopy. Marginal adaptation was measured in unbonded (%VVF) and bonded (%XVF) specimens by computerized X-ray microtomography (micro-XCT). The % linear length of the interfacial gaps along the cavity margins (%LD) and the ...

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Tetrahydrofuran as alternative solvent in dental adhesive systems

Dental Materials — Mon, 26 Oct 2009 16:59:42 +0100

Abstract: Objective: To evaluate the influence of tetrahydrofuran (THF) on the resin-to-dentin microtensile bond strength (μTBS) after water storage, for 24h and 6 months, and to compare its behavior with that of traditional solvents.Methods: Seven versions of monomer/solvent mixtures (primers) were prepared using the following solvent and water combinations: (1) THF, (2) acetone, (3) ethanol, (4) water, (5) THF/water, (6) acetone/water and (7) ethanol/water. An experimental adhesive resin was also synthesized to compare adhesive systems with the different primers. Forty-two bovine incisors, randomly separated into seven groups, had their superficial coronal dentin exposed. After acid-etching and rinsing, the excess water was removed from the surface with absorbent paper. Each experimenta...

Mechanical behavior of facial prosthetic elastomers after outdoor weathering

Dental Materials — Mon, 26 Oct 2009 16:59:42 +0100

Conclusion: The effect of irradiation time on the mechanical behavior was introduced through its effect on the models’ parameters. The hypothesis was rejected since changes were observed in the model parameters. (Source: Dental Materials)

Effects of light penetration and smear layer removal on adhesion of post–cores to root canal dentin by self-etching adhesives

Dental Materials — Mon, 26 Oct 2009 16:59:41 +0100

This study investigated the effects of light penetration and removal of smear layer on the adhesive properties of self-etching adhesives to root canal dentin when using fiber posts.Methods: Altogether 54 human incisors and premolars were decoronated, and the roots after preparing the post space were randomly assigned into six groups. Three groups were treated with a light-cured self-etching adhesive and the other three with a dual-cured self-etching adhesive. In a further sub-division, the first group was light-cured with an irradiation unit; the second was light-cured with the irradiation unit and a light-guiding attachment; and the third was light-cured with the irradiation unit and the attachment after removing smear layer by EDTA and NaOCl. Then, a glass-fiber post was luted into the p...

Bond strength durability of a resin composite on a reinforced ceramic using various repair systems

Dental Materials — Mon, 26 Oct 2009 16:59:41 +0100

This study compared the durability of repair bond strength of a resin composite to a reinforced ceramic after three repair systems.Methods: Alumina-reinforced feldspathic ceramic blocks (Vitadur-α®) (N=30) were randomly divided into three groups according to the repair method: PR-Porcelain Repair Kit (Bisco) [etching with 9.5% hydrofluoric acid+silanization+adhesive]; CJ-CoJet Repair Kit (3M ESPE) [(chairside silica coating with 30μm SiO2+silanization (ESPE®-Sil)+adhesive (Visio™-Bond)]; CL-Clearfil Repair Kit [diamond surface roughening, etching with 40% H3PO4+Clearfil Porcelain Bond Activator+Clearfil SE Bond)]. Resin composite was photo-polymerized on each conditioned ceramic block. Non-trimmed beam specimens were produced for the microtensile bond strength (μTBS) tests. In order...

John W. McLean 1925–2009

Dental Materials — Mon, 26 Oct 2009 16:59:41 +0100

John McLean was a Clinician—Scientist nonpareil in the traditions of Tomes, Black and Rushton. (Source: Dental Materials)

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Editorial Board

Dental Materials — Mon, 26 Oct 2009 16:59:40 +0100

(Source: Dental Materials)

The Adherence of platelets to adsorbed albumin by receptor-mediated recognition of binding sites exposed by adsorption-induced unfolding.

Biomaterials — Mon, 26 Oct 2009 00:00:00 +0100

Authors: Sivaraman B, Latour RA Although albumin (Alb) is the most abundant plasma protein, it is considered to be non-adhesive to platelets, as it lacks any known amino acid sequences for binding platelet receptors. Recent studies have suggested that platelets adhere to adsorbed Alb by mechanisms linked to its conformational state. To definitively address this issue we used circular dichroism (CD) spectropolarimetry to characterize the conformation of Alb adsorbed on a broad range of surface chemistries from a wide range of Alb solution concentrations, with platelet adhesion examined using a lactate dehydrogenase (LDH) assay and scanning electron microscopy (SEM). Our results prove that platelets bind to adsorbed Alb through receptor-mediated processes, with binding sites in Alb expos...

Biological responses to hydroxyapatite surfaces deposited via a co-incident microblasting technique.

Biomaterials — Mon, 26 Oct 2009 00:00:00 +0100

In this study two methods for creating a HA layer on metal alloys that employ micro-blasting have been evaluated to determine if the inclusion of an abrasive agent can enhance the in vitro and in vivo performance of the modified surface. The first method employs direct micro-blasting using HA as the abrasive media, while the second employs a simultaneous blasting with an alumina abrasive and coincident blasting with HA as a dopant. Whereas, both methods were found to produce a surface which was enriched with HA, the respective microstructures created were significantly different. Detailed surface characterisation revealed that the use of the abrasive produced disruption of the metal surface without producing detectable incorporation of alumina particles. Roughening of the metal surface in ...

Surfaces modified with nanometer-thick silver-impregnated polymeric films that kill bacteria but support growth of mammalian cells.

Biomaterials — Mon, 26 Oct 2009 00:00:00 +0100

Authors: Agarwal A, Weis TL, Schurr MJ, Faith NG, Czuprynski CJ, McAnulty JF, Murphy CJ, Abbott NL Silver is widely used as a biocidal agent in ointments and wound dressings. However, it has also been associated with tissue toxicity and impaired healing. In vitro characterization has also revealed that typical loadings of silver employed in ointments and dressings ( approximately 100mug/cm(2)) lead to cytotoxicity. In this paper, we report the results of an initial study that sought to determine if localization of carefully controlled loadings of silver nanoparticles within molecularly thin films immobilized on surfaces can lead to antimicrobial activity without inducing cytotoxicity. Polymeric thin films of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were prepare...

Osteogenic differentiation of human amniotic fluid-derived stem cells induced by bone morphogenetic protein-7 and enhanced by nanofibrous scaffolds.

Biomaterials — Sat, 24 Oct 2009 00:00:00 +0100

Authors: Sun H, Feng K, Hu J, Soker S, Atala A, Ma PX Amniotic fluid-derived stem cells (AFSCs) are becoming an important source of cells for regenerative medicine given their apparent advantages of accessibility, renewal capacity and multipotentiality. In the intermediate stage between the embryonic stem cells (ESCs) and adult stem cells, AFSCs may have a distinct mechanism to choose their fate. Unfortunately, until now, little is known about how bone morphogenetic proteins (BMPs) control the osteoblastic differentiation of AFSCs, especially on 3D scaffolds. Our research shows that human AFSCs (hAFSCs) can be induced for osteoblastic differentiation by rhBMP-7, and hAFSCs respond to rhBMP-7 more strongly than human mesenchymal stem cells (hMSCs). As synthetic ECM, scaffolds play a cen...

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Toxicological characteristics of nanoparticulate anatase titanium dioxide in mice.

Biomaterials — Sat, 24 Oct 2009 00:00:00 +0100

Authors: Duan Y, Liu J, Ma L, Li N, Liu H, Wang J, Zheng L, Liu C, Wang X, Zhao X, Yan J, Wang S, Wang H, Zhang X, Hong F In an effort to examine liver injury, immune response, and other physiological effects in mice caused by intragastric administration of nanoparticulate anatase titanium dioxide (5nm), we assessed T lymphocytes, B lymphocyte and NK lymphocyte counts, hematological indices, biochemical parameters of liver functions, and histopathological changes in nanoparticulate titanium dioxide -treated mice. Indeed, mice treated with higher dose nanoparticulate titanium dioxide displayed a reduction in body weight, an increase in coefficients of the liver and histopathological changes in the liver. Specifically, in these nanoparticulate titanium dioxide -treated mice, interleukin-...

Nanoscale protein-based memory device composed of recombinant azurin.

Biomaterials — Sat, 24 Oct 2009 00:00:00 +0100

Authors: Kim SU, Yagati AK, Min J, Choi JW In this present study, a nanoscale protein-based memory device consisting of recombinant azurin with its cysteine residues modified by site-directed mutagenesis method has been developed. Cysteine residues were modified to directly coordinate with the gold surface without use of any chemical linkers. Cyclic voltammetry (CV) method was used to measure the redox behavior of the immobilized azurin. Open-circuit potential amperometry (OCPA) technique allowed observing the memory characteristics including "write", "erase" and "read" functions of a nanoscale memory device. The variations in topology and the electron transfer properties, under the application of redox potentials, of the azurin adsorbed on Au was accomplished with electrochemical scan...

Molecular design of chitosan gene delivery systems with an optimized balance between polyplex stability and polyplex unpacking.

Biomaterials — Sat, 24 Oct 2009 00:00:00 +0100

Authors: Strand SP, Lelu S, Reitan NK, de Lange Davies C, Artursson P, Vårum KM Chitosan is an attractive gene delivery vehicle, but the criteria and strategies for the design of efficient chitosan gene delivery systems remain unclear. The purpose of this work was to investigate how the strength of the charge-based interaction between chitosan and DNA determines the gene expression levels and to design chitosan vectors with an optimized balance between polyplex stability and polyplex unpacking. Using 21 formulations based on low molecular weight chitosans with constant charge density and a number-average degree of polymerization (DPn) in the range of 21-88 (M(w) 4.7-33kDa), we studied the relationship between the chain length and the formulation properties, cellular uptake of poly...

The influence of rat mesenchymal stem cell CD44 surface markers on cell growth, fibronectin expression, and cardiomyogenic differentiation on silk fibroin - Hyaluronic acid cardiac patches.

Biomaterials — Sat, 24 Oct 2009 00:00:00 +0100

Authors: Yang MC, Chi NH, Chou NK, Huang YY, Chung TW, Chang YL, Liu HC, Shieh MJ, Wang SS Since MSCs contain an abundant of CD44 surface markers, it is of interesting to investigate whether CD44 on rat MSC (rMSCs) influenced cell growth, fibronectin expression and cardiomyogenic differentiation on new SF/HA cardiac patches. For this investigation, we examined the influences of rMSCs with or without a CD44-blockage treatment on the aforementioned issues after they were cultivated, and further induced by 5-aza on SF and SF/HA patches. The results showed that the relative growth rates of rMSCs cultured on cultural wells, SF/HA patches without or with a CD44-blockage treatment were 100%, 208.9+/-7.1 (%) or 48.4+/-6.0 (%) (n=3, for all), respectively, after five days of cultivations. Moreo...

Neuronal cell growth on iridium oxide.

Biomaterials — Sat, 24 Oct 2009 00:00:00 +0100

In this study the biocompatibility of pure iridium and different iridium oxides that differ characteristically in their surface roughness was investigated using two different biological test systems, insect and vertebrate neurons. Iridium oxide surfaces were coated with Concanavalin A and poly-(d)-lysine. In detailed investigations (R(a) value determination, contact angle measurement, marker enzyme assay) the surface characteristics of non-modified and coated iridium oxide films were analysed, demonstrating that the materials can be successfully coated. Furthermore, we show that locust neurons grow well on all substrates tested, while chicken neurons need coated surfaces for proper adhesion. Increasing the roughness of iridium oxide films, which in principle could improve cell adhesion, di...

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Pharmacological activity and protein phosphorylation caused by nitric oxide-releasing microparticles.

Biomaterials — Sat, 24 Oct 2009 00:00:00 +0100

Authors: Yoo JW, Choe ES, Ahn SM, Lee CH Nitric oxide (NO)-releasing microparticles were developed as a potential treatment option against various blood flow irregulations including sexual dysfunction, atherosclerosis and metal stent-induced restenosis. Polymeric microparticles containing diethylenetriamine diazeniumdiolate (DETA NONOate), a NO donor, were prepared using modified double-emulsion solvent evaporation method to maximize the loading efficacy and stability of DETA NONOate. The pharmacological effects of the NO-releasing microparticles were evaluated by examining the changes in the vaginal blood flow in rats. The effects of NO on the phosphorylation of protein kinase C (PKC) and mitogen activated protein (MAP) kinases in excised vaginal mucosa, such as extracellular signal-r...

Acrylic Copolymers as Candidates for Drug-Eluting Coating of Vascular Stents

Journal of Biomaterials Applications — Fri, 23 Oct 2009 11:11:35 +0100

The aim of the present work is the synthesis and characterization of polymer materials showing good adhesion, drug loading, and delivery properties, for potential cardiovascular application. In particular, poly(methylmethacrylate-co-acrylic acid) copolymers are prepared in different compositions by a radical polymerization and investigated as potential materials to coat metallic stents and to carry out a local drug release. Films obtained by dissolving the copolymer in an appropriate organic solvent (also loaded with an anti-restenosis drug, such as tacrolimus) are investigated: physicochemical properties, adhesiveness to metallic stent material, and kinetics of drug release in physiological environment are studied. (Source: Journal of Biomaterials Applications)

Effect of Cryoprotectant Incubation Time on Handling Properties of Allogeneic Tendons Prepared for Knee Ligament Reconstruction

Journal of Biomaterials Applications — Fri, 23 Oct 2009 11:11:35 +0100

This study concludes that an 8-h cryoprotectant incubation time is detrimental to qualitative allogeniec tibialis posterior tendon properties. Both groups tended to improve with longer rehydration times, however the 8-h incubation group remained actively dehydrated as evidenced by its smaller diameter and poorer tissue handling properties. Suboptimally rehydrated tendons would be more likely to accrue damage during allograft preparation or during implantation. (Source: Journal of Biomaterials Applications)

Enhanced Regeneration of Critical Bone Defects Using a Biodegradable Gelatin Sponge and {beta}-Tricalcium Phosphate with Bone Morphogenetic Protein-2

Journal of Biomaterials Applications — Fri, 23 Oct 2009 11:11:35 +0100

We examine the osteogenicity of a sponge biomaterial consisting of a biodegradable mixture of gelatin and β-tricalcium phosphate (βTCP) that bound bone morphogenetic protein 2 (BMP-2) in critical-sized bone defects in rats. Gelatin-βTCP sponges containing either phosphate buffered saline or incorporating BMP-2 are implanted into 5 mm diameter bone defects created in rat mandibles. We assess the defects biweekly for 8 weeks following implantation. There is significantly higher osteoinductive activity and significantly more Gla-osteocalcin content at bone-defect healing sites treated with gelatin-βTCP sponges incorporating BMP-2 than there is in those treated with sponges that did not contain BMP-2. Histologically, new bone that contains bone marrow and that is connected ...

Evaluation of Parenteral Depot Insulin Formulation using PLGA and PLA Microparticles

Journal of Biomaterials Applications — Fri, 23 Oct 2009 11:11:35 +0100

PLGA and PLA microparticles entrapping insulin are prepared by solvent evaporation method and are evaluated in diabetes-induced rat for its efficacy in maintaining blood sugar level from a single intramuscular dose. In vitro release of insulin from PLGA and PLA microparticles are 75.35 ± 1.73% and 67.536 ± 2.23%, respectively in 168 h (7 days). Released insulin from polymer particles are mostly in monomeric form without aggregation. Optimal use of stabilizers during particle formulation helps in reducing protein denaturation and thus results in stabilized insulin-loaded polymer particles. Intramuscular administration of insulin-loaded PLGA (50 : 50) and PLA microparticles (equivalent to 25 IU insulin/kg of animal weight) in alloxaninduced diabetic rats result in 53.86 ±...

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Review Paper: Role of Aluminum in Glass-ionomer Dental Cements and its Biological Effects

Journal of Biomaterials Applications — Fri, 23 Oct 2009 11:11:34 +0100

The role of aluminum in glass-ionomers and resin-modified glass-ionomers for dentistry is reviewed. Aluminum is included in the glass component of these materials in the form of Al2O3 to confer basicity on the glass and enable the glass to take part in the acid—base setting reactions. Results of studies of these reactions by FTIR and magic-angle spinning (MAS)-NMR spectroscopy are reported and the role of aluminum is discussed in detail. Aluminum has been shown to be present in the glasses in predominantly 4-coordination, as well as 5- and 6-coordination, and during setting a proportion of this is converted to 6-coordinate species within the matrix of the cement. Despite this, mature cements may contain detectable amounts of both 4- and 5-coordinate aluminum. Aluminum has been found ...

Structural properties of materials created through freeze casting

Acta Materialia — Fri, 23 Oct 2009 00:00:00 +0100

Abstract: Upon freezing of an aqueous suspension of colloidal particles, ice platelets or dendrites with high aspect ratios are formed that engulf or reject the particles, depending on their size and the velocity of the advancing ice front. As the particles are pushed between the growing crystals, concentrated regions of colloidal particles are formed. Recent experiments have exploited this to create strong, porous materials with a well-controlled microstructure. We investigate this process by means of molecular dynamics simulations, focusing on the effect of the ice front velocity on the structure of the resulting material. We develop a model that accounts for particle engulfment or rejection by the ice front, and study both columnar and lamellar geometries. The degree of order of the res...

Small intestine submucosa sponge for in vivo support of tissue-engineered bone formation in the presence of rat bone marrow stem cells.

Biomaterials — Fri, 23 Oct 2009 00:00:00 +0100

Authors: Kim KS, Lee JY, Kang YM, Kim ES, Kim GH, Rhee SD, Cheon HG, Kim JH, Min BH, Lee HB, Kim MS The aim of the current study was to visualize new bone formed in vivo on a small intestine submucosa (SIS) sponge used as a tissue-engineered scaffold for the repair of damaged bone. The SIS sponge provided a three-dimensional pore structure, and supported good attachment and viability of rat bone marrow stem cells (rBMSCs). To examine bone regeneration, we prepared full-thickness bilateral bone defects in the rat crania, and then treated the defects with an implanted SIS sponge or PGA mesh without or with rBMSCs, or left the defects untreated. Bone defects were evaluated by micro-CT and histologically after 2 and 4 weeks. Micro-CT demonstrated a trend toward a decrease in bone void in b...

pH-sensitive carbonate apatite as an intracellular protein transporter.

Biomaterials — Fri, 23 Oct 2009 00:00:00 +0100

In this study, we characterized protein/carbonate apatite complexes as an intracellular protein delivery system and we checked intracellular delivery of proteins by carbonate apatite nanoparticles in vitro. Fluorescently-labeled bovine serum albumin as a model protein was effectively delivered into nearly 100% of HeLa cells by the simple addition of protein/carbonate apatite complexes to the cells. Confocal microscopic imaging suggested the endosomal release of protein delivered with carbonate apatite. And intracellularly delivered ss-galactosidase did not lose its enzymatic activity. These results suggested that intracellular delivery system of protein using pH-sensitive carbonate apatite carrier with a very simple procedure will be a highly effective method to the biological and clinical...

A guanidinylated bioreducible polymer with high nuclear localization ability for gene delivery systems.

Biomaterials — Fri, 23 Oct 2009 00:00:00 +0100

Authors: Kim TI, Lee M, Kim SW Guanidinylated bioreducible polymer (GBP) was developed for gene delivery systems utilizing cellular penetrating ability of guanidine groups. GBP could retard pDNA from a weight ratio of 5 completely in agarose gel electrophoresis but pDNA was released from GBP polyplexes even at a weight ratio of 20 in reducing condition (2.5mm DTT) due to their biodegradation. GBP also could construct 200 nm-sized and positively charged ( approximately 30mV) polyplex nanoparticles with pDNA. The cytotoxicity of GBP was found to be minimal and GBP showed about 8 folds improved transfection efficiency than a scaffold polymer, poly(cystaminebisacrylamide-diaminohexane) (poly(CBA-DAH)) and even higher transfection efficiency than PEI25k in mammalian cell lines. Its high cel...

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Long-term biostability of self-assembling protein polymers in the absence of covalent crosslinking.

Biomaterials — Fri, 23 Oct 2009 00:00:00 +0100

We report herein that a self-assembling, recombinant elastin-mimetic triblock copolymer elicited minimal inflammatory response and displayed robust in vivo stability for periods exceeding 1 year, in the absence of either chemical or ionic crosslinking. Specifically, neither a significant inflammatory response nor calcification was observed upon implantation of test materials into the peritoneal cavity or subcutaneous space of a mouse model. Moreover, serial quantitative magnetic resonance imaging, evaluation of pre- and post-explant ultrastructure by cryo-high resolution scanning electron microscopy, and an examination of implant mechanical responses revealed substantial preservation of form, material architecture, and biomechanical properties, providing convincing evidence of a non-chemic...

The stimulation of angiogenesis and collagen deposition by copper.

Biomaterials — Fri, 23 Oct 2009 00:00:00 +0100

Authors: Gérard C, Bordeleau LJ, Barralet J, Doillon CJ Copper is known to trigger endothelial cells towards angiogenesis. Different approaches have been investigated to develop vascularisation in biomaterials. The angiogenic and healing potential of copper ions in combination with two major angiogenic factors was examined. A 3D culture system in which, under stimulation by FGF-2 and to a lesser degree with VEGF, endothelial cells assembled into structures resembling to an angiogenic process was used. The combination of CuSO(4) with increasing doses of VEGF or FGF-2 enhanced the complexity of angiogenic networks in a significant manner. In vivo studies were also conducted by incorporating FGF-2 with CuSO(4) in a cylindrical collagen-based scaffold. CuSO(4) enhanced significantly t...

Local delivery of a collagen-binding FGF-1 chimera to smooth muscle cells in collagen scaffolds for vascular tissue engineering.

Biomaterials — Thu, 22 Oct 2009 00:00:00 +0100

Authors: Pang Y, Wang X, Ucuzian AA, Brey EM, Burgess WH, Jones KJ, Alexander TD, Greisler HP We investigated the delivery of R136K-CBD (a collagen-binding mutant chimera of fibroblast growth factor-1) with a type I collagen scaffold as the delivery vehicle to smooth muscle cells (SMCs) for vascular tissue engineering. The binding affinity of R136K-CBD to 3-D collagen scaffolds was investigated both in the presence and absence of cells and/or salts. 2-D and 3-D visualization of delivery of R136K-CBD into SMCs were accomplished by combined fluorescent and reflection confocal microscopy. The mitogenic effect of collagen-immobilized R136K-CBD on SMCs in 3-D collagen was studied by Cyquant assay at different time intervals. In the group devoid of salt and cells, no detectable release of R1...

Ring-opening metathesis polymerization-based synthesis of polymeric nanoparticles for enhanced tumor imaging in vivo: Synergistic effect of folate-receptor targeting and PEGylation.

Biomaterials — Thu, 22 Oct 2009 00:00:00 +0100

Authors: Miki K, Oride K, Inoue S, Kuramochi Y, Nayak RR, Matsuoka H, Harada H, Hiraoka M, Ohe K We have synthesized amphiphilic copolymers using ring-opening metathesis polymerization (ROMP), a copper-catalyzed dipolar click reaction, and osmium-catalyzed dihydroxylation. The resulting copolymers were easily conjugated with folate and dye (indocyanine green) moieties, using a transamidation method. The copolymers exhibited high water solubility and formed nanometer-sized self-assemblies in aqueous medium. The amphiphilic copolymers modified by dihydroxylation of the polymer backbone exhibited much lower cmc values than the non dihydroxylated copolymer. Copolymers conjugated with folate moieties reduced the fluorescence intensity of aqueous polymer solutions both in vitro and in vivo, ...

Signalling pathways involved in the activation of dendritic cells by layered double hydroxide nanoparticles.

Biomaterials — Thu, 22 Oct 2009 00:00:00 +0100

Authors: Li A, Qin L, Zhu D, Zhu R, Sun J, Wang S Layered double hydroxide (LDH) nanoparticles are attractive as potential drug vectors for the targeting not only of tissues, but also of intracellular organelles, and particularly the acidic endolysosomes created after cell endocytosis. The purpose of this study was to investigate the ability of LDH nanoparticles designed as vectors to activate dendritic cells (DCs), as measured by various cellular functions. The study also explored the possible signaling pathway through which the LDH nanoparticles exerted their effects on the cellular functions of DCs. First, LDH nanoparticles with different ratios of Mg(OH)(2) to Al(OH)(3) (1:1, 2:1 and 3:1, called R1, R2 and R3 respectively) were optimized and had a hydrodynamic diameter of 57nm with...

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Creation of lysine-deficient mutant lymphotoxin-alpha with receptor selectivity by using a phage display system.

Biomaterials — Thu, 22 Oct 2009 00:00:00 +0100

Authors: Yoshioka Y, Watanabe H, Morishige T, Yao X, Ikemizu S, Nagao C, Ahmad S, Mizuguchi K, Tsunoda SI, Tsutsumi Y, Mukai Y, Okada N, Nakagawa S The cytokine lymphotoxin-alpha (LTalpha) activates various biological functions through its three receptor subtypes, tumor necrosis factor receptor 1 (TNFR1), TNFR2 and herpes virus entry mediator (HVEM), but the relative contribution of each receptor to each function is unclear. Therefore it is important to create mutant LTalpha with receptor selectivity for optimized cancer therapy and the analysis of receptor function. Here, we attempted to create a lysine-deficient mutant LTalpha with TNFR1-selective bioactivity using a phage display technique. We obtained the TNFR1-selective mutant LTalpha R1selLT, which contained the mutations K19N, K...

Trimethylated chitosan-conjugated PLGA nanoparticles for the delivery of drugs to the brain.

Biomaterials — Wed, 21 Oct 2009 00:00:00 +0100

Authors: Wang ZH, Wang ZY, Sun CS, Wang CY, Jiang TY, Wang SL Trimethylated chitosan (TMC) surface-modified poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles (TMC/PLGA-NP) were synthesized as a drug carrier for brain delivery. TMC was covalently coupled to the surface of PLGA nanoparticles (PLGA-NP) via a carbodiimide-mediated link. The zeta potential of TMC/PLGA-NP was about 20mV with a mean diameter around 150nm. 6-coumarin loaded PLGA-NP and TMC/PLGA-NP were injected into the caudal vein of mice, and fluorescent microscopy of brain sections showed a higher accumulation of TMC/PLGA-NP in the cortex, paracoele, the third ventricle and choroid plexus epithelium, while no brain uptake of PLGA-NP was observed. There was no pronounced difference in cell viability between TMC/PLGA-NP and...

The exploitation of differential endocytic pathways in normal and tumor cells in the selective targeting of nanoparticulate chemotherapeutic agents.

Biomaterials — Wed, 21 Oct 2009 00:00:00 +0100

In conclusion, we describe major difference in interactions of cl-micelles with cancer and normal cells that can lead to development of novel drug delivery system with reduced side effects and higher efficacy in cancer chemotherapy. PMID: 19853293 [PubMed - as supplied by publisher] (Source: Biomaterials)

Myogenic differentiation of human bone marrow mesenchymal stem cells on a 3D nano fibrous scaffold for bladder tissue engineering.

Biomaterials — Wed, 21 Oct 2009 00:00:00 +0100

Authors: Tian H, Bharadwaj S, Liu Y, Ma H, Ma PX, Atala A, Zhang Y Current strategies for engineering bladder tissues include a bladder biopsy for in vitro cell expansion for use in reconstructive procedures. However, this approach cannot be used in patients with bladder cancer who need a complete bladder replacement. Bone marrow mesenchymal stem cells (BMSC) might be an alternative cell source to better meet this need. We investigated the effects of soluble growth factors, bladder extracellular matrix (ECM), and 3D dynamic culture on cell proliferation and differentiation of human BMSC into smooth muscle cells (SMC). Myogenic growth factors (PDGF-BB and TGF-beta1) alone, or combined either with bladder ECM or dynamic cultures, induced BMSC to express smooth muscle-specific genes and p...

Biomaterial mediated epithelial-mesenchymal interaction of salivary tissue under serum free condition.

Biomaterials — Wed, 21 Oct 2009 00:00:00 +0100

Authors: Yang TL, Hsiao YC, Lin SJ, Lee HW, Lou PJ, Ko JY, Young TH Many organs develop from epithelial-mesenchymal interactions such that in order to regenerate these organs, it might be a preferable strategy to recapitulate this process. However, in the current culture system designed for tissue interaction, the supplement of serum is required. The aim of this study is to explore the possibility of reproducing epithelial-mesenchymal interaction and ensuing morphogenesis in a serum-free condition. In accordance with the previous studies, by using a standard model of murine fetal submandibular gland (SMG), the tissue interaction and the morphogenesis were largely dependent on serum. Nonetheless, when tissue recombinants were cultivated on polyvinylidene fluoride (PVDF), but not on othe...

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Doxycycline loaded poly(ethylene glycol) hydrogels for healing vesicant-induced ocular wounds.

Biomaterials — Wed, 21 Oct 2009 00:00:00 +0100

In conclusion, the current studies demonstrate that the doxycycline-PEG hydrogels accelerate corneal wound healing after vesicant injury offering a therapeutic option for ocular mustard injuries. PMID: 19853296 [PubMed - as supplied by publisher] (Source: Biomaterials)

A collagen-mimetic triple helical supramolecule that evokes integrin-dependent cell responses.

Biomaterials — Wed, 21 Oct 2009 00:00:00 +0100

Authors: Yamazaki CM, Kadoya Y, Hozumi K, Okano-Kosugi H, Asada S, Kitagawa K, Nomizu M, Koide T Collagen is an abundantly distributed extracellular matrix protein in mammalian bodies that maintains structural integrity of the organs and tissues. Besides its function as a structural protein, collagen has various biological functions which regulate cell adhesion, migration and differentiation. In order to develop totally synthetic collagen-surrogates, we recently reported a basic concept for preparing collagen-like triple helical supramolecules based on the self-assembly of staggered trimeric peptides with self-complementary shapes. In this paper, we add one of the specific cellular functions of the native collagen to the collagen-mimetic supramolecule. We synthesized a self-assembling ...

Tissue-specific gene delivery via nanoparticle coating.

Biomaterials — Tue, 20 Oct 2009 00:00:00 +0100

Authors: Harris TJ, Green JJ, Fung PW, Langer R, Anderson DG, Bhatia SN The use of biomaterials for gene delivery can potentially avoid many of the safety concerns with viral gene delivery. However, the efficacy of polymeric gene delivery methods is low, particularly in vivo. One significant concern is that the interior and exterior composition of polymeric gene delivery nanoparticles are often coupled, with a single polymer backbone governing all functions from biophysical properties of the polymer/DNA particle to DNA condensation and release. In this work we develop electrostatically adsorbed poly(glutamic acid)-based peptide coatings to alter the exterior composition of a core gene delivery particle and thereby affect tissue-specificity of gene delivery function in vivo. We find tha...

The relationship between platelet adhesion on surfaces and the structure versus the amount of adsorbed fibrinogen.

Biomaterials — Tue, 20 Oct 2009 00:00:00 +0100

Authors: Sivaraman B, Latour RA While platelet adhesion to biomaterial surfaces is widely recognized to be related to adsorbed fibrinogen (Fg), it has remained controversial whether platelet adhesion is in response to the adsorbed amount or the adsorbed conformation of this protein. To address this issue, we designed a series of platelet adhesion studies to clearly separate these two factors, thus enabling us to definitively determine whether it is the amount or the conformation of adsorbed Fg that mediates platelet response. Fg was adsorbed to a broad range of surface chemistries from a wide range of solution concentrations, with the amount and conformation of adsorbed Fg determined by absorbance and circular dichroism (CD) spectropolarimetry, respectively. Platelet adhesion response ...

MedWorm: Materials Science

2010 Acta Materialia, Inc. Gold Medal Award

Editors for Acta Materialia

Detection of polyunsaturated omega-6 fatty acid in human malignant prostate tissue by 1D and 2D high-resolution magic angle spinning NMR spectroscopy

Efficient siRNA delivery to mammalian cells using layered double hydroxide nanoparticles.

2010 Acta Materialia, Inc. Gold Medal Award

Editors for Scripta Materialia

Editors for Acta Materialia

Engineering fibrin matrices: The engagement of polymerization pockets through fibrin knob technology for the delivery and retention of therapeutic proteins.

The effect of VEGF on the myogenic differentiation of adipose tissue derived stem cells within thermosensitive hydrogel matrices.

The induction of tumor apoptosis in B16 melanoma following STAT3 siRNA delivery with a lipid-substituted polyethylenimine.

The effect of timing in the administration of hepatocyte growth factor to modulate BMP-2-induced osteoblast differentiation.

A nitric oxide releasing, self assembled peptide amphiphile matrix that mimics native endothelium for coating implantable cardiovascular devices.

Immunological response to tissue-engineered cartilage derived from auricular chondrocytes and a PLLA scaffold in transgenic mice.

Dinuclear metal(II) complexes of polybenzimidazole ligands as carriers for DNA delivery.

Self-initiated surface grafting with poly(2-methacryloyloxyethyl phosphorylcholine) on poly(ether-ether-ketone).

The role of protein assembly in dynamically tunable bio-optical tissues.

Effects of VEGF temporal and spatial presentation on angiogenesis.

Study of the adhesion improvement in hippocampal cells on collagen/chitosan- modified silicon surfaces

A biomimetic hydrogel based on methacrylated dextran-graft-lysine and gelatin for 3D smooth muscle cell culture.

Different types of article in JMBBM.

Effect of fluorapatite additive on densification and mechanical properties of tricalcium phosphate.

An entropy spring model for the Young's modulus change of biodegradable polymers during biodegradation.

Minimizing specimen length in elastic testing of end-constrained cancellous bone.

Mechanical evaluation by patient-specific finite element analyses demonstrates therapeutic effects for osteoporotic vertebrae.

Development of biomedical porous titanium filled with medical polymer by in-situ polymerization of monomer solution infiltrated into pores.

Mechanical characterisation of polyurethane elastomer for biomedical applications.

Investigation of the mechanical interaction of the trabecular core with an external shell using rapid prototype and finite element models.

Wear behavior of light-cured dental composites filled with porous glass-ceramic particles.

A novel constitutive model of skeletal muscle taking into account anisotropic damage.

Dependence of in vitro fatigue properties of PMMA bone cement on the polydispersity index of its powder.

Anisotropic swelling and mechanical behavior of composite bacterial cellulose-poly(acrylamide or acrylamide-sodium acrylate) hydrogels.

Viscoelastic behavior of discrete human collagen fibrils.

Fracture of tooth enamel from incipient microstructural defects.

Friction of F-actin knots.

Transversely isotropic tensile material properties of skeletal muscle tissue.

A composite kidney stone phantom with mechanical properties controllable over the range of human kidney stones.

Statistical Analysis of Misorientation Distributions From Growth Selection Experiments in Iron–3% Si

Microstructure and Texture of in Situ Heavily Drawn Cu–Nb Composites

Influence of Rolling Temperature on the Perfection Degree of Recrystallization Cube Texture in Nickel

Effect of Zonal Isolation on the Kinetics of Sintering a Particulate Body

Quantification of Minor Texture Components by Hard X-Rays

Recrystallization in a Hot Deformed Al-Mg-Si Alloy: The Effect of Fine Precipitates

Microtexture Studies of PST and PZT Ceramics and PZT Thin Film by Electron Backscatter Diffraction Patterns

On The Peculiarities of X-Ray Determination of Crystallographic Texture in Samples After Testing Wear Resistance

Effective Elastic Properties of Textured Cubic Polycrystals

Pole Figure Inversion Using Finite Elements Over Rodrigues Space

Preface

Depth Resolved Strain and Phase Mapping of Dissimilar Friction Stir Welds Using High Energy Synchrotron Radiation

Tensile Deformation Induced Texture Transformation in Austenitic Stainless Steel

Torsion Texture Measurements With High-Energy Synchrotron Radiation on NiAl

Full Stress Tensor Determination in A textured Aerospace Aluminium Alloy Plate Using synchrotron X-Ray Diffraction

Use of Synchrotron Diffraction Data for Describing Crystal Structure and Crystallographic Phase Analysis of R-Phase NiTi Shape Memory Alloy

Influence of Grain Number on Graphite Quantitative Texture Study

Applications on High-Energy X-Rays to Stress Measurements of Thermal Barrier Coatings

High-Energy X-Rays: A tool for Advanced Bulk Investigations in Materials Science and Physics

High-Resolution Imaging of Texture and Microstructure by the Moving Detector Method

Hot-Extruded and Cold-Rolled Textures of the Matrix Aluminum in Deformation Processed Two-Phase Nb/Al Metal-Metal Composites

Intensity Correction in Texture Measurement of Polycrystalline Thin Films by X-Ray Diffraction

Effect of Gravity on the Kinetics of Consolidation of Powder Bodies

Injectable biodegradable hydrogels with tunable mechanical properties for the stimulation of neurogenesic differentiation of human mesenchymal stem cells in 3D culture.

Promotion of osteoblast proliferation on complex coacervation-based hyaluronic acid - recombinant mussel adhesive protein coatings on titanium.

Surface-energy dependent contact activation of blood factor XII.

The contribution of plasmid design and release to in vivo gene expression following delivery from cationic polymer modified scaffolds.

Editors for Acta Materialia

The use of RGDGWK-lipopeptide to selectively deliver genes to mouse tumor vasculature and its complexation with p53 to inhibit tumor growth.

Nanoparticles functionalised with recombinant single chain Fv antibody fragments (scFv) for the magnetic resonance imaging of cancer cells.

The delivery of superoxide dismutase encapsulated in polyketal microparticles to rat myocardium and protection from myocardial ischemia-reperfusion injury.

Engineering a scaffold-free 3D tumor model for in vitro drug penetration studies.

Self-Assembly of phospholipid-analogous hyperbranched polymers nanomicelles for drug delivery.

Partly PEGylated polyamidoamine dendrimer for tumor-selective targeting of doxorubicin: The effects of PEGylation degree and drug conjugation style.

Density functional theory calculations and molecular dynamics simulations of the adsorption of biomolecules on graphene surfaces.

The performance of a fly-larva shell-derived chitosan sponge as an absorbable surgical hemostatic agent.

The effect of PEGylation of mesoporous silica nanoparticles on nonspecific binding of serum proteins and cellular responses.

The repair of large segmental bone defects in the rabbit with vascularized tissue engineered bone.

Surface characteristics and in vitro biocompatibility of titanium anodized in a phosphoric acid solution at different voltages

Table of Contents

Editorial Board

Masthead

Role of NFκB in an Animal Model of Complex Regional Pain Syndrome–type I (CRPS-I)