powered by FreeFind
Articles about Biomaterials
For the Biomaterials Industry - Hundreds of Biomaterials Articles! Polymers, Composites, Ceramics, Alloys... Biomaterials Articles
Biomaterials Articles
Biomaterials Articles
Biomaterials Articles

Record 3601 to 3620
First Page Previous Page Next Page Last Page
Saccharide-peptide hybrid copolymers as biomaterials
Metzke, M., N. O'Connor, et al. (2005), Angew Chem Int Ed Engl 44(40): 6529-33.

Sacrificial Bonds and Hidden Length: Unraveling Molecular Mesostructures in Tough Materials
Fantner, G. E., E. Oroudjev, et al. (2005), Biophys J
Abstract: Sacrificial bonds and hidden length in structural molecules and composites have been found to greatly increase the fracture toughness of biomaterials (1) by providing a reversible, molecular-scale energy-dissipation mechanism. This mechanism relies on the energy, of order 100 eV, needed to reduce entropy and increase enthalpy as molecular segments are stretched after being released by the breaking of weak bonds, called sacrificial bonds(2). This energy is relatively large compared to the energy needed to break the polymer backbone, of order a few eV. In many biological cases, the breaking of sacrificial bonds has been found to be reversible, thereby additionally providing a "self-healing" property to the material(1,3). Due to the nanoscopic nature of this mechanism, single molecule force spectroscopy using an atomic force microscope (4-6) has been a useful tool to investigate this mechanism. Especially when investigating natural molecular constructs, force vs. distance curves quickly become very complicated (7). In this work we propose various types of sacrificial bonds, their combination and how they appear in single molecule force spectroscopy measurements. We find that by close analysis of the force spectroscopy curves, additional information can be obtained about the molecules and their bonds to the native constructs.

Safety and efficacy of nonanimal stabilized hyaluronic acid for improvement of mouth corners
Carruthers, J., A. W. Klein, et al. (2005), Dermatol Surg 31(3): 276-80.
Abstract: BACKGROUND: Esthetic concern with downturned mouth corners ("mouth frown") is increasing in the aging baby-boomer generation. A new technique to offer structural support using the recently approved filler nonanimal stabilized hyaluronic acid (NASHA; Restylane, Q-med Inc., Uppsala, Sweden) is described. METHOD: Fifteen women with prominent downturned mouth corners met the inclusion criteria for the study. All were photographed before and at 1 week, 3 months, 4.5 months, and 6 months after treatment using a standardized clinical photographic system. NASHA was injected using a standardized technique with nerve block anesthesia to ensure patient comfort. RESULTS: All 15 women noted swelling, redness, and some local discomfort for several days after the injection. All noted an improvement in the downward angulation of their mouth corners at the first post-treatment visit, with at least partial improvement maintained through the 6-month post-treatment follow-up visit. CONCLUSIONS: NASHA injection to support the age-related downturn of lateral lip corners was effective, safe, and well tolerated in a small prospective study of middle-aged female subjects. Esthetic satisfaction was greatest in the first 3 months post-treatment, but 40% of subjects still noted improvement at the 6-month follow-up visit.

Safety of gold in stapes surgery
Kwok, P., M. Schuster, et al. (2005), Biomaterials 26(34): 7132-5.
Abstract: Gold prostheses in middle ear surgery were found to have a higher extrusion rate than prostheses made from titanium. Incidences of deafness after insertion of a gold piston into the vestibule during stapes surgery have been observed. The aim of this study was to find out to what degree gold cations can diffuse from the prosthesis piston into the perilymph. For this, gold prostheses were incubated in artificial perilymph for four months, after which the gold content of the perilymph was analysed. As gold exhibits a special behaviour in complex fluids like the perilymph, a new analysing method was developed. The results show that gold does leak out of the pistons, that it can be reliably measured and that the amount of gold reaching the perilymph depends on the contact area. As the amount of gold measured in the perilymph stays far below the toxic level, it is very unlikely that the gold cations diffusing from a stapes prosthesis into the perilymph have a toxic effect on the inner ear hair cells. Inflammatory or allergic reactions to gold induced by direct tissue contact, however, cannot be excluded.

Salt-assisted acid hydrolysis of chitosan to oligomers under microwave irradiation
Xing, R., S. Liu, et al. (2005), Carbohydr Res 340(13): 2150-3.
Abstract: The effect of inorganic salts such as sodium chloride on the hydrolysis of chitosan in a microwave field was investigated. While it is known that microwave heating is a convenient way to obtain a wide range of products of different molecular weights only by changing the reaction time and/or the radiation power, the addition of some inorganic salts was shown to effectively accelerate the degradation of chitosan under microwave irradiation. The molecular weight of the degraded chitosan obtained by microwave irradiation was considerably lower than that obtained by traditional heating. Moreover, the molecular weight of degraded chitosan obtained by microwave irradiation assisted under the conditions of added salt was considerably lower than that obtained by microwave irradiation without added salt. Furthermore, the effect of ionic strength of the added salts was not linked with the change of molecular weight. FTIR spectral analyses demonstrated that a significantly shorter time was required to obtain a satisfactory molecular weight by the microwave irradiation-assisted inorganic salt method than by microwave irradiation without inorganic salts and conventional technology.

Sampling of working-zone air and biomaterials and unification of MPC values
Liska, D. (1985), J Hyg Epidemiol Microbiol Immunol 29(1): 23-7.
Abstract: Some points concerning the strategy of working-zone-air sampling, the sampling plan and the manner of sampling biological materials have been discussed. In drawing up an air-sampling plan, the following items should be paid attention to: production technology, organization, physicochemical properties and composition of the raw materials, intermediate and final products, potential sources of spread of harmful substances and their spread from these sources, the time picture of workers' presence, the analytical method and the concentration of the harmful substances in the working-zone atmosphere. In order to unify MPC's within the frame of CMEA, one should be informed about the norms and standardized methods in force in each country, work out and unify principles for sampling the air and biomaterials and work out a project of a unified way of evaluating analysis results.

Scaffold implants for the controlled release of heparan sulfate (HS) and other glycosaminoglycan (GAG) species: this could facilitate the homing of adult stem cells for tissue/organ regeneration
Heng, B. C., H. Liu, et al. (2005), Med Hypotheses 65(2): 414-5.

Scaffolds and biomaterials for tissue engineering: a review of clinical applications
Vats, A., N. S. Tolley, et al. (2003), Clin Otolaryngol Allied Sci 28(3): 165-72.
Abstract: Tissue engineering is a multidisciplinary area of research aimed at regeneration of tissues and restoration of organ function. This is achieved through implantation of cells/tissues grown outside the body or by stimulating cells to grow into an implanted matrix. In this short review, we discuss the use of biomaterials, in the form of scaffolds, for tissue engineering and review clinical applications to otorhinolaryngology-head and neck surgery.

Scaffolds for liver tissue engineering
Hammond, J. S., I. J. Beckingham, et al. (2006), Expert Rev Med Devices 3(1): 21-27.
Abstract: This review focuses on the expanding role for biomaterials and polymer scaffolds in liver tissue engineering. Studies are subdivided into in vitro and in vivo approaches. The in vitro section of the review discusses the challenges specific to liver tissue engineering, and how the choice of scaffold and its structure influences the success of the regenerative medicine strategy. The in vivo section evaluates early attempts to stimulate liver repair with cell and growth factor therapies, their failings and how current approaches aim to solve these problems.

Scaled interfacial activity of proteins at a hydrophobic solid/aqueous-buffer interface
Krishnan, A., Y. H. Liu, et al. (2005), J Biomed Mater Res A 75(2): 445-57.
Abstract: Contact-angle goniometry confirms that interfacial energetics of protein adsorption to the hydrophobic solid/aqueous-buffer (solid-liquid, SL) surface is not fundamentally different than adsorption to the aqueous-buffer/air (liquid-vapor, LV) interface measured by pendant-drop tensiometry. Adsorption isotherms of 9 globular blood proteins with molecular weight (MW) spanning from 10 to 1000 kDa on methyl-terminated self-assembled monolayer surfaces demonstrate that (i) proteins are weak surfactants, reducing contact angles by no more than about 15 degrees at maximum solution concentrations (approximately 10 mg/mL); (ii) the corresponding dynamic range of spreading pressure Pi(a) < 20 mN/m; and (iii) the maximum spreading pressure Pi(max) (a) for these diverse proteins falls within a relatively narrow 5 mN/m band. As with adsorption to the LV interface, we find that concentration scaling substantially alters perception of protein interfacial activity measured by Pi(a). Proteins appear more similar than dissimilar on a weight/volume basis whereas molarity scaling reveals a systematic ordering by MW, suggesting that adsorption is substantially driven by solution concentration rather than diversity in protein amphilicity. Scaling as a ratio-to-physiological-concentration demonstrates that certain proteins exhibit Pi(max)(a) at-and-well-below physiological concentration whereas others require substantially higher solution concentration to attain Pi(max)(a). Important among this latter category of proteins is blood factor XII, assumed by the classical biochemical mechanism of plasma coagulation to be highly surface active, even in the presence of overwhelming concentrations of other blood constituents such as albumin and immunoglobulin that are shown by this work to be among the class of highly surface-active proteins at physiologic concentration. The overarching interpretation of this work is that water plays a dominant, controlling role in the adsorption of globular-blood proteins to hydrophobic surfaces and that energetics of hydration control the amount of protein adsorbed to poorly water-wettable biomaterials.

Scanning electrochemical microscopy of metallic biomaterials: reaction rate and ion release imaging modes
Gilbert, J. L., S. M. Smith, et al. (1993), J Biomed Mater Res 27(11): 1357-66.
Abstract: The Scanning Electrochemical Microscope (SECM) is a nonoptical scanning microscopic instrument capable of imaging highly localized electrical currents associated with charge transfer reactions on metallic biomaterials surfaces. The SECM operates as an aqueous electrochemical cell under bipotentiostatic control with a microelectrode and sample independently biased as working electrodes. Microelectrode current and position is recorded as it is scanned very near a metallurgically polished planar sample surface. To date, the SECM has imaged metallic biomaterials surfaces in oxygen reaction rate imaging (ORRI) and ion release and deposition imaging (IRDI) modes. In ORRI, sample and microelectrode are biased at sufficiently negative potentials to reduce absorbed oxygen. As the microelectrode scans areas of active oxygen reduction, localized diffusion fields with decreased oxygen solution concentrations are encountered and resultant decrements in microelectrode current are observed. In IRDI mode the sample is positively biased and the microelectrode is negatively biased. The microelectrode detects anodic dissolution products with highest currents being observed over the most active areas. Performance of the SECM has been evaluated on Ni minigrids, gamma-1 Hg-Ag dental amalgam crystals, and sintered beads of Co-Cr-Mo alloy which represent significantly different geometries and corrosion processes to help demonstrate the potential of this instrument. The SECM is a valuable tool for imaging microelectrochemical processes on the surfaces of metallurgically polished metallic biomaterials samples and a wide variety of other surfaces of biological interest where charge transfer reactions occur. The SECM allows selective biasing of metallic biomaterials surfaces and Faradaic reactions can be selectively imaged while the surface is in the active, passive, or transpassive state.

Scanning probe microscopy for the characterization of biomaterials and biological interactions
Garrison, M. D. and B. D. Ratner (1997), Ann N Y Acad Sci 831: 101-13.
Abstract: The scanning probe microscopies provide a unique view of biological and biomedical systems at a nanoscale appropriate to appreciate molecular events. The advent of these methods has brought the ability to acquire quantitative information at the molecular level. Given the proliferation of microscopes and associated methods, the probability for important discoveries is high. If tempered with an appreciation for the potential for artifacts, the SPMs may revolutionize our view of biological systems and biomaterials interactions with those systems.

Schisis/cavitation of the MemoryLens optic
Kleinmann, G., D. J. Apple, et al. (2005), J Cataract Refract Surg 31(9): 1841-2.

Schwann cell behavior in three-dimensional collagen gels: evidence for differential mechano-transduction and the influence of TGF-beta 1 in morphological polarization and differentiation
Rosner, B. I., T. Hang, et al. (2005), Exp Neurol 195(1): 81-91.
Abstract: Schwann cells (SCs) cultured on and within magnetically aligned collagen gels were examined for their abilities to spread and exhibit contact guidance, two functions that are relevant to their potential enhancement of neurite migration and regeneration in entubulation repair of transection-type nerve injuries. Cells seeded at or near the surfaces of gels abandoned their initially spherical shapes, adopting spread morphologies rapidly compared to cells within the gels. Those few cells within the gels that did spread exhibited marked contact guidance responses, aligning strongly with the aligned collagen fibrils. Spreading of cells in gels could not be induced by varied cell concentration, collagen density, mitogen presence, inclusion of soluble laminin, or use of fibrin gel in lieu of collagen. However, cells that settled at the interface between collagen gel layers during gellation of the top layer above a preformed bottom layer were highly spread. This suggests that a differential mechanical interaction across the cell at an interface, where at least one surface presents constituents of the basal lamina, permits the Schwann cell to rapidly revert to a spread, differentiated phenotype. Unlike other reagents, TGF-beta1 was able to induce significant SC spreading as early as 4 h post-seeding. Consistent with the differential-mechanical cue mechanism, TGF-beta1 appears to facilitate this response, at least in part, by upregulating beta1 integrin expression, thereby enabling the SC to more acutely detect these local cues in the mechanical environment.

Science/industry: problematics of the European cooperative research in the biomaterials/biodevices area
Doddoli, R. (1998), Biomaterials 19(16): 1433-9.
Abstract: The problematics created by the promotion of scientific and technological cooperation and interaction between European research bodies and industries in biomaterials/biodevices area, is presented in this work. This statement approaches the theme of cooperative research on a European level. It aims also to highlight the different problems that arise at the time of the proposal of a research project, during the setting up of a partnership with different specialities. A research project in a multi-partnership would have to bring benefits to each of the participants. Before arriving at this stage, one would have to take into account the fact that such inter-cooperation would be efficient only after delicate preparation prior to the commitment of partners because, for each of them, aims and objectives are different. This work also hopes to bring supplementary ideas to the officers of the European Commission for future frameworks.

Screening biomaterials with a new in vitro method for potential calcification: porcine aortic valves and bovine pericardium
Mavrilas, D., J. Kapolos, et al. (2004), J Mater Sci Mater Med 15(6): 699-704.
Abstract: Calcification is still a major cause of failure of implantable biomaterials. A fast and reliable in vitro model could contribute to the study of its mechanisms and to testing different anticalcification techniques. In this work, we attempted to investigate the potential calcification of biomaterials using an in vitro model. We purposed to test the ability of this model to screening possible anticalcification efficacy of different biomaterials. Porcine heart valve (PAV) and bovine pericardial (BP) tissues, fixed with glutaraldehyde were immersed into biological mimicking solution, where the pH and the initial concentrations of calcium and phosphoric ions were kept stable by the addition of precipitated ions during calcification. Kinetics of calcification was continuously monitored. The evaluation of biomaterials was carried out by comparing the kinetic rates of formation of calcific deposits. After 24 h, the calcific deposits on PAVs were found to be developed at significant higher rates (ranged from 0.81 x 10(-4)-2.18 x 10(-4)mol/min m2) than on BP (0.19 x 10(-4)-0.52 x 10(-4)mol/min m2) (one-way ANOVA, p < 0.05) depending on the experimental conditions (supersaturation of the solution). Parallel tests for similar biomaterials implanted subcutaneously in animal (rat) model showed after 49 days that significant higher amounts of total minerals deposited on PAV (236.73+/-139.12, 9 animals mg minerals/g dry net tissue) (mean+/-standard deviation) compared with that formed on BP (104.36+/-79.21, #9 mg minerals/g dry net tissue) (ANOVA, p < 0.05). There is evidence that in vitro calcification was correlated well with that of animal model and clinical data.

Sealing effectiveness of materials used in furcation perforation in vitro
Tsatsas, D. V., H. A. Meliou, et al. (2005), Int Dent J 55(3): 133-41.
Abstract: Objectives: In this study the sealing ability of various materials used to repair furcation perforations was evaluated. Design: Ninety human molars were endodontically treated and a perforation was made in the pulp chamber floor using a round bur. The teeth were inserted into a moistened flower sponge and perforation sites were sealed with one of the following materials: Mineral Trioxide Aggregate (ProRootM), Super-EBA, Vitremer, Hemarcol together with Super-EBA, Hemarcol together with Vitremer, Tricalcium phosphate together with AH26, Cavit W and amalgam. After eight months, the sealing effectiveness of the materials was evaluated in a double-blinded trial under a video-microscope by detecting the penetration of silver nitrate solution (50%w/w) in longitudinal tooth sections. Results: Perforation sites filled with Hemarcol together with Vitremer or with MTA exhibited statistically less silver stain penetration while Cavit W or Tricalcium phosphate together with AH26 sealer failed to effectively seal the perforation sites. Conclusions: MTA alone or Vitremer in combination with a collagen sponge can be used effectively in the treatment of perforations in a furcation area.

Sealing smooth enamel surfaces with a newly devised adhesive patch: a radiochemical in vitro analysis
Schmidlin, P. R., M. Zehnder, et al. (2005), Dent Mater 21(6): 545-50.
Abstract: OBJECTIVES: To assess the enamel-protective potential of a newly devised adhesive patch when used as a smooth surface sealant. METHODS: Eighty enamel discs were prepared from bovine lower central incisors and then irradiated. Twenty specimens were treated with one of three sealing options: enamel bond in a two-step application, the prototype of an adhesive patch, or a flowable resin. Unsealed enamel served as positive controls. Loss of apatite was determined using a radiochemical liquid scintillation method after immersion of the samples in saliva or lactic acid (n=10 per treatment group) each for up to 21 days, during which this experimental and control enamel surfaces were exposed to ten toothbrush strokes per day. Quantitative liquid scintillation data were verified by polarized light microscopy. RESULTS: With lactic acid exposure, a double layer of enamel bonding showed better enamel protection than untreated controls, but was significantly less effective than the adhesive patch or filled composite (P<0.05). No significant differences were noted between the latter two treatments. SIGNIFICANCE: It was concluded that the adhesive patch under investigation merits further studies to assess its potential as an inter-proximal sealant.

Search for ideal biomaterials to cultivate human osteoblast-like cells for reconstructive surgery
Wiedmann-Al-Ahmad, M., R. Gutwald, et al. (2005), J Mater Sci Mater Med 16(1): 57-66.
Abstract: In this study we cultured human osteoblast-like cells on 16 different biomaterials to find an optimal biomaterial for subsequent use in reconstructive surgery. The tested biomaterials can be divided into five groups: collagen-based membranes of bovine, equine or calf origin, tricalcium phosphate based membranes (alpha and beta), hyaluronic acid based, anorganic bovine bone and anorganic silicone-based membranes. Cell proliferation and cell colonization (Environmental Scanning Electron Microscope, ESEM) analysis were performed.The results of the study demonstrated that four of the examined biomaterial/cell constructs showed a very good proliferation rate and cell density: No. 3 (Tissue Vlies), No. 7 (Sepra film), No. 16 (Biobrane) and No. 17 (Biomend). No favourable group of biomaterials was noticeable. Moreover, the results indicate that these four biomaterials as a part of bone constructs are the best tools for engineering new bone tissue. In contrast, biomaterials No. 19a (Bio-Oss) and 19b (Bio-Oss Collagen) showed the lowest proliferation rates. The result of No. 19b was improved by treatment in the perfusion chamber for 48 h as well as by additional use of vacuum. The present study is an important base for further analysis of biomaterials and consequently for the development of tissue engineering.

Search for the insertion element IS256 within the ica locus of Staphylococcus epidermidis clinical isolates collected from biomaterial-associated infections
Arciola, C. R., D. Campoccia, et al. (2004), Biomaterials 25(18): 4117-25.
Abstract: Staphylococcus epidermidis biofilm-forming strains produce a polysaccharide intercellular adhesin (PIA), which mediates bacterial cell aggregation and favours the colonisation on prosthetic implants. PIA synthesis is regulated by the icaADBC locus. In vitro, by repeated subcultures of a biofilm-producing strain, the loss of the ability to produce biofilm appears associated with the insertion of the IS256 element into the ica locus. This study was aimed (i) to investigate if the five genes of ica locus are always all present in different strains of S. epidermidis, and (ii) to search if IS256 insertion naturally occurs in ica locus without making recourse to the experimental procedure of repeated subcultures of strains. 120 S. epidermidis clinical isolates from peri-prosthesis infections were investigated both by an original multiplex PCR analysis of the ica genes and by PCR amplification of the IS256 element. Also two reference strains (the biofilm-negative S. epidermidis ATCC 12228 and the biofilm-forming ATCC 35984 [RP62A]) and two biofilm-negative RP62A-derived acriflavin mutants (D9 and HAM892) were analysed. D9 e HAM892 were for the first time shown to contain in ica locus, at the base 3319, a 1300-bp insertion with a DNA sequence corresponding to IS256. Among the 120 clinical isolates, 51 (43%) turned out completely ica-positive, 69 completely ica-negative (57%). The genes of the ica locus appear, in all cases of the present collection, strictly linked each other, so they are either all present or all absent. In this collection, IS256 was present in eight out of the 69 ica-negative strains and in 34 out of the 51 ica-positive strains. IS256, also when present in bacterial genomic DNA, was never found inside the ica locus, thus suggesting that insertion/excision of this element is not a natural occurring mechanism for off/on switching of biofilm production.

First Page Previous Page Next Page Last Page

Last Modified: 8 February 2006