Biomaterials.info - Resources for Engineers

Record 3881 to 3900

Surface-enhanced Raman spectroscopy using silver-coated porous glass-ceramic substrates
Pan, Z., A. Zavalin, et al. (2005), Appl Spectrosc 59(6): 782-6.
Abstract: Surface-enhanced Raman scattering (SERS) has been studied using a silver-coated porous glass-ceramic material as a new type of substrate. The porous glass-ceramic is in the CaO-TiO2-P2O5 system prepared by controlled crystallization and subsequent chemical leaching of the dense glass-ceramic, leaving a solid skeleton with pores ranging in size from 50 nm to submicrometer. Silver was coated on the surface of the porous glass-ceramic by radio frequency (RF) sputtering or e-beam evaporation in vacuum. SERS spectra of excellent quality were obtained from several dyes and carboxylic acid molecules, including rhodamine 6G, crystal violet, isonicotinic acid, and benzoic acid, using this new substrate. This new substrate showed a good compatibility with these molecules. The porous glass ceramic with a nanometer-structured surface accommodated both test molecules and silver film. The absorbed molecules were therefore better interfaced with silver for surface-enhanced Raman scattering.

Surface-initiated ATRP of HEA from nanocrystal alpha-Fe2O3 under ultrasonic irradiation
Liu, P., L. Zhang, et al. (2005), J Nanosci Nanotechnol 5(10): 1713-7.
Abstract: Core/shell poly(beta-hydroethyl acrylate) (PHEA) encapsulated nanocrystal alpha-Fe2O3 nanospheres (Fe2O3@PHEA) were successfully prepared by the surface-initiated atom transfer radical polymerization (SI-ATRP) of beta-hydroethyl acrylate (HEA), a functional monomer, from the surfaces of the nanocrystal Fe2O3 modified with bromo-acetamide groups with the catalysts of 1,10-phenanthroline and Cu(I)Br under ultrasonic irradiation at room temperature in water. The products, Fe2O3@PHEA, were characterized by elemental analysis (EA), FT-IR, XRD, XPS and TEM. The percentage of grafting (PG%) of 38.95% and the conversion of HEA (C%) of 14.29% at room temperature for 6 h with ultrasonic irradiation were higher than the 22.41% and 8.22%, respectively, found for samples prepared by electromagnetic stirring. This demonstrated that the ultrasonic irradiation improves the SI-ATRP of HEA.

Surface-MALDI mass spectrometry in biomaterials research
Griesser, H. J., P. Kingshott, et al. (2004), Biomaterials 25(20): 4861-75.
Abstract: Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) has been used for over a decade for the determination of purity and accurate molecular masses of macromolecular analytes, such as proteins, in solution. In the last few years the technique has been adapted to become a new surface analysis method with unique capabilities that complement established biomaterial surface analysis methods such as XPS and ToF-SSIMS. These new MALDI variant methods, which we shall collectively summarize as Surface-MALDI-MS, are capable of desorbing adsorbed macromolecules from biomaterial surfaces and detecting their molecular ions with high mass resolution and at levels much below monolayer coverage. Thus, Surface-MALDI-MS offers unique means of addressing biomaterial surface analysis needs, such as identification of the proteins and lipids that adsorb from multicomponent biological solutions in vitro and in vivo, the study of interactions between biomaterial surfaces and biomolecules, and identification of surface-enriched additives and contaminants. Surface-MALDI-MS is rapid, experimentally convenient, overcomes limitations in mass resolution and sensitivity of established biochemical techniques such as SDS-PAGE, and can in some circumstances be used for the quantitative analysis of adsorbed protein amounts. At this early stage of development, however, limitations exist: in some cases proteins are not detectable, which appears to be related to tight surface binding. This review summarizes ways in which Surface-MALDI-MS methods have been applied to the study of a range of issues in biomaterials surfaces research.

Surface-reactive biomaterials in osteoblast cultures: an ultrastructural study
Sautier, J. M., J. R. Nefussi, et al. (1992), Biomaterials 13(6): 400-2.
Abstract: The tissue/biomaterial interface reactions of three biomaterials selected as candidates for hard tissue replacement were studied at the electron microscopical level after incubation with enzymatically isolated rat bone cells. An electron-dense layer was routinely observed between hydroxyapatite, coral, cytodex polymer and the neighbouring cells. This layer was visible before bone formation occurred, and was collagen free. The ultrastructural features revealed a needle-shaped filamentous layer continuous with coral material, whereas hydroxyapatite or cytodex/tissue interface was granular in appearance. These different structures may indicate reactive surfaces, depending on the composition of the substrate.

Surfactant polymers designed to suppress bacterial (Staphylococcus epidermidis) adhesion on biomaterials
Vacheethasanee, K. and R. E. Marchant (2000), J Biomed Mater Res 50(3): 302-12.
Abstract: We describe a series of surfactant polymers designed as surface-modifying agents for the suppression of bacterial adhesion on biomaterials. The surfactant polymers consist of a poly(vinyl amine) backbone with hydrophilic poly(ethylene oxide) (PEO) and hydrophobic hexanal (Hex) side chains (PVAm/PEO:Hex). Surface modification is accomplished by simple dip coating from aqueous solution, from which surfactant polymers undergo spontaneous surface-induced assembly on hydrophobic biomaterials. The stability of PVAm/PEO:Hex on pyrolytic graphite (HOPG) and polyethylene (PE) was demonstrated by the absence of detectable desorption under flow conditions of pure water over a 24-h period. PEO surfactant polymers with four different PEO:Hex ratios (1:1.4, 1:2.5, 1:4.6, and 1:10.7) and a dextran surfactant polymer were compared with respect to S. epidermidis adhesion under dynamic flow conditions. Suppression of S. epidermidis adhesion was achieved for all modified surfaces over the shear range 0-15 dyn/cm(2). The effectiveness depended on the surfactant polymer composition such that S. epidermidis adhesion to modified surfaces decreased significantly with increasing PEO packing density. Modified HOPG was more effective in reducing bacterial adhesion compared with the corresponding modification on PE, which we attribute to the presence of defects in surfactant polymer assembly on PE. Our results are discussed from the perspective of critical factors, such as optimal PEO packing density and hydration thickness, that contribute to the effectiveness of surfactant polymers to shield a biomaterial from adhesive bacterial interactions.

Surfactant-assisted synthesis of water-soluble and biocompatible semiconductor quantum dot micelles
Fan, H., E. W. Leve, et al. (2005), Nano Lett 5(4): 645-8.
Abstract: We report a simple, rapid approach to synthesize water-soluble and biocompatible fluorescent quantum dot (QD) micelles by encapsulation of monodisperse, hydrophobic QDs within surfactant/lipid micelles. Analyses of UV-vis and photo luminescence spectra, along with transmission electron microscopy, indicate that the water-soluble semiconductor QD micelles are monodisperse and retain the optical properties of the original hydrophobic QDs. The QD micelles were shown to be biocompatible and exhibited little or no aggregation when taken up by cultured rat hippocampal neurons.

Surgical biomaterials and differential colonization by Staphylococcus epidermidis
Oga, M., Y. Sugioka, et al. (1988), Biomaterials 9(3): 285-9.
Abstract: The data presented in this communication demonstrate preferential colonization of certain biomaterials by Staphylococcus epidermidis. Using a laminar flow biomaterial colonization chamber and surgical-grade biomaterials (stainless steel, aluminium ceramic, methyl methacrylate and high-density polyethylene), the pattern of colonization was quantitated using plate count techniques and electron microscopy. Under comparable conditions, methyl methacrylate was colonized by S. epidermidis in greater numbers than the other biomaterials. Increased bacterial colonization and slime production on methyl methacrylate was time-dependent and 15 times higher than on stainless steel and aluminium and four times higher than on high-density polyethylene. The data reveal that certain biomaterials may promote infection by favouring colonization by potential pathogens. This variable should be explored extensively in an in vivo setting because of its implication in clinical infections.

Surgical sutures and infection: a biomaterial evaluation
Edlich, R. F., P. H. Panek, et al. (1974), J Biomed Mater Res 8(3): 115-26.

Surgical technique and biomaterials for totally implanted port catheter systems
Campisi, C., M. Assenza, et al. (1997), J Chemother 9(2): 155-6.

Surgicel Nu-Knit hemostat for bleeding control of fragile sternum
Mair, H., I. Kaczmarek, et al. (2005), J Thorac Cardiovasc Surg 130(2): 605-6.

Survival of endothelial cells in vitro on Paclitaxel-loaded coronary stents
Prasad, C. K., K. R. Resmi, et al. (2005), J Biomater Appl 19(4): 271-86.
Abstract: Coronary stents that are developed for use with balloon angioplasty are known to cause acute occlusion and long-term stenosis. It is likely that a controlled release of drugs at the site of stent implantation might inhibit the proliferation of vascular smooth muscle cells (VSMC) and reduce restenosis. However, if the drug is necrotic and affects cell survival near the implant, it may interrupt the local tissue regeneration. Different methods have been used for the immobilization of drugs with stents to get an effective concentration that inhibits cell proliferation. The objective of this study is to assess the effectiveness of Paclitaxel-loaded stents by immobilization with a biodegradable polymer, to inhibit cell proliferation. The cells used for the evaluation are human umbilical vein endothelial cells (HUVEC) and the proliferation rate of these cells on the drug-coated stent is compared against an uncoated stent for a 72-h period. Evaluations were also made to differentiate between cell apoptosis and necrosis to prove that the drug released is not deleterious to the surrounding tissue.While a similar initial cell adhesion is observed in bare and coated stents, the proliferation of HUVEC is negligible when grown on a drug-coated stent (p < 0.001). By specific staining techniques, the cells on the drug-coated stents are found to be apoptotic and not necrotic, throughout the evaluation period. In vitro leukocyte adhesion and platelet deposition on the drug-coated stents are found to be low when they are exposed to human blood and platelet-rich plasma (PRP), suggesting that the coated stents may not be thrombogenic in vivo. Therefore, drug coating of stents using the described technique may have a considerable promise for the prevention of neointimal proliferation, restenosis, and associated failure of angioplasty.

Susceptibility of prosthetic biomaterials to infection
Losanoff, J. E. and J. M. Millis (2005), Surg Endosc

Sustained production of H2O2 on irradiated TiO2- fluoride systems
Maurino, V., C. Minero, et al. (2005), Chem Commun (Camb)(20): 2627-9.
Abstract: UV irradiation of fluorinated TiO(2) suspensions in water, in the presence of oxygen and a hole scavenger, leads to the production of H(2)O(2) with steady state concentration levels up to 1.3 millimolar; the H(2)O(2) formation rate follows the TiO(2) surface speciation, being maximum when the surface is completely covered by [triple bond]Ti-F groups; these results outline the importance of surface speciation on the photocatalytic process.

Sustained release characteristics of tablets prepared with mixed matrix of sodium carrageenan and chitosan: effect of polymer weight ratio, dissolution medium, and drug type
Bani-Jaber, A. and M. Al-Ghazawi (2005), Drug Dev Ind Pharm 31(3): 241-7.
Abstract: The interpolymeric complexation of carrageenan and chitosan was investigated for its effect on drug release from polymeric matrices in comparison to single polymers. For this purpose, matrices with carrageenan: chitosan (CG:CS) ratios of 100%, 75%, 50%, 25%, and 0% were prepared at 1:1 drug to polymer ratio. The effect of dissolution medium and drug type on drug release from the formulations was addressed. Two model drugs were utilized: diltiazem HCl (DZ) as a salt of a basic drug and diclofenac Na (DS) as a salt of an acidic drug. Three dissolution media were used: water, simulated gastric fluid (SGF), and simulated intestinal fluid (SIF). Some combinations of the two polymers showed remarkable sustained release effect on DZ in comparison to the single polymers in water and SGF. However, no apparent effect for the combination on DZ release was shown in SIF. The medium effect was explained by the necessity of chitosan ionization, which could be attained by the acidic SGF or microacidic environment created by the used acidic salt of DZ in water, but not in SIF. An interaction between the medium type and CG:CS ratio was also found. With DS, the polymer combinations had similar dissolution profiles to those of the single polymers in water and SIF, which was explained by the lack of chitosan ionization by the medium or the drug basic salt. The dissolution profiles could not be obtained in SGF, which was attributed to the conversion of DS into diclofenac free acid. The importance of chitosan ionization for its interaction with CG to have an effect on the release of DS was demonstrated by performing dissolution of SGF presoaked tablets of DS in SIF, which showed an effect of combining the two polymers on sustaining the drug release.

Suturing for surgical success
Kurtzman, G. M., L. H. Silverstein, et al. (2005), Dent Today 24(10): 96-102; quiz 103.

Symbiosis of biotechnology and biomaterials: applications in tissue engineering of bone and cartilage
Reddi, A. H. (1994), J Cell Biochem 56(2): 192-5.
Abstract: The three ingredients for the successful tissue engineering of bone and cartilage are regulatory signals, cells, and extracellular matrix. Recent advances in cellular and molecular biology of the growth and differentiation factors have set the stage for a symbiosis of biotechnology and biomaterials. Recent advances permit one to enunciate the rules of architecture for tissue engineering of bone and cartilage. The purification and cloning of bone morphogenetic proteins (BMPs) and growth factors such as platelet derived growth factors (PDGF), transforming growth factor-beta (TGF-beta), and insulin-like growth factors (IGF-I) will allow the design of an optimal combination of signals to initiate and promote development of skeletal stem cells into cartilage and bone. Successful and optimal bone and cartilage formation is a synergy of inductive and conductive strategies governed by biomechanics, optimal load bearing, and motion. BMPs function as inductive signals. Biomaterials (both natural and synthetic) mimic the extracellular matrix and play a role in conduction of bone and cartilage. Examples of biomaterials include hydroxyapatite, polyanhydrides, polyphosphoesters, polylactic acid, and polyglycolic acid. The prospects for novel biomaterials are immense, and they likely will be a fertile growth industry. Cooperative ventures between academia and industry and technology transfer from the federal government augur well for an exciting future for clinical applications.

Symptomatic myocardial bridging--a niche indication for drug-eluting stents?
Ng, E., H. Jilaihawi, et al. (2005), Int J Cardiol 99(3): 463-4.

Synchrotron X-ray microtomography (on a micron scale) provides three-dimensional imaging representation of bone ingrowth in calcium phosphate biomaterials
Weiss, P., L. Obadia, et al. (2003), Biomaterials 24(25): 4591-601.
Abstract: This study used synchrotron X-ray microtomography on a micron scale to compare three-dimensional (3D) bone ingrowth after implantation of various calcium phosphate bone substitutes in a rabbit model. The advantage of using this new method for the study of biomaterials was then compared with histomorphometry for analysis of interconnection and bone ingrowth. The study focused on the newly formed bone-biomaterial interface. Macroporous Biphasic Calcium Phosphate (MBCP) ceramic blocks and two different injectable calcium phosphate biomaterials [an injectable bone substitute (IBS) consisting of a biphasic calcium phosphate granule suspension in hydrosoluble polymer and a calcium phosphate cement material (CPC)] were studied after in vivo implantation.Absorption or phase-contrast microtomography was performed with the dedicated set-up at beamline ID22. Experimental spatial resolution was between 1 and 1.4 microm, depending on experimental radiation. All calcium phosphates tested showed osteoconduction. IBS observations after 3D reconstruction showed interconnected bioactive biomaterial with total open macroporosity and complete bone ingrowth as early as 3 weeks after implantation. This experimentation was consistent with two-dimensional histomorphometric analysis, which confirmed its suitability for biomaterials. This 3D study relates the different types of bone substitution to biomaterial architecture. As porosity and interconnection increase, bone ingrowth becomes greater at the expense of the bone substitute: IBS>MBCP>CPC.

Synergistic effect of poly(ethylenimine) on the transfection efficiency of galactosylated chitosan/DNA complexes
Kim, T. H., S. I. Kim, et al. (2005), J Control Release 105(3): 354-66.
Abstract: The use of chitosan for gene delivery is limited due to the low transfection efficiency and difficulty in transfecting into a variety of cell types, especially the hepatoma cells. In order to solve this problem, lactobionic acid (LA) bearing galactose group was coupled with water-soluble chitosan (WSC) for liver specificity and poly(ethylenimine) (PEI) was combined to galactosylated chitosan (GC)/DNA complexes to enhance the transfection efficiency. For initial study, the effect of PEI on the transfection efficiency of WSC/DNA complex was studied in HeLa, A549 and 293 T cells, and bafilomycin A1 was used to ascertain the mechanism of synergistic effect. Transfection efficiency, cytotoxicity, and physicochemical properties of GC/DNA complex combined with PEI were investigated to determine the potential for the hepatocyte-targeting. The combination of PEI with WSC/DNA and GC/DNA complex dramatically increased the luciferase expression 10- to 1000-fold in various cell lines, and the synergistic effect was proved to be induced by proton sponge effect of PEI. The transfection of GC/DNA complex in HepG2 was much higher than that of WSC/DNA even after combination with PEI, and was highly inhibited in the presence of galactose. Cytotoxicity of PEI was much decreased by combination with GC/DNA complex. And PEI was proved to be coated on the surface of GC/DNA complex through the ionic interaction.

Synergistic effects of micropatterned biodegradable conduits and Schwann cells on sciatic nerve regeneration
Rutkowski, G. E., C. A. Miller, et al. (2004), J Neural Eng 1(3): 151-7.
Abstract: This paper describes a novel biodegradable conduit that provides a combination of physical, chemical and biological cues at the cellular level to facilitate peripheral nerve regeneration. The conduit consists of a porous poly(D,L-lactic acid) (PDLLA) tubular support structure with a micropatterned inner lumen. Schwann cells were pre-seeded into the lumen to provide additional trophic support. Conduits with micropatterned inner lumens pre-seeded with Schwann cells (MS) were fabricated and compared with three types of conduits used as controls: M (conduits with micropatterned inner lumens without pre-seeded Schwann cells), NS (conduits without micropatterned inner lumens pre-seeded with Schwann cells) and N (conduits without micropatterned inner lumens, without pre-seeded Schwann cells). The conduits were implanted in rats with 1 cm sciatic nerve transections and the regeneration and functional recovery were compared in the four different cases. The number or size of regenerated axons did not vary significantly among the different conduits. The time of recovery, and the sciatic function index, however, were significantly enhanced using the MS conduits, based on qualitative observations as well as quantitative measurements using walking track analysis. This demonstrates that biodegradable micropatterned conduits pre-seeded with Schwann cells that provide a combination of physical, chemical and biological guidance cues for regenerating axons at the cellular level offer a better alternative for repairing sciatic nerve transactions than conventional biodegradable conduits.

First Page

Last Page