Biomaterials.info - Resources for Engineers

Record 2981 to 3000

New experimental approach to study host tissue response to surgical mesh materials in vivo
Laschke, M. W., J. M. Haufel, et al. (2005), J Biomed Mater Res A 74(4): 696-704.
Abstract: Implantation of surgical meshes is a common procedure to increase abdominal wall stability in hernia repair. To improve biocompatibility of the implants, sophisticated in vivo animal models are needed to study inflammation and incorporation of biomaterials. Herein, we have established a new model that allows for the quantitative analysis of host tissue response and vascular ingrowth into surgical mesh materials in vivo. Ultrapro meshes were implanted into dorsal skinfold chambers of Syrian golden hamsters. Angiogenesis, microhemodynamics, microvascular permeability, and leukocyte-endothelial cell interaction of the host tissue were analyzed in response to material implantation over a 2-week period using intravital fluorescence microscopy. Mesh implantation resulted in a short-term activation of leukocytes, reflected by leukocyte accumulation and adherence in postcapillary venules. This cellular inflammatory response was accompanied by an increase of macromolecular leakage, indicating loss of integrity of venular endothelial cells. Angiogenesis started at day 3 after implantation by protrusion of capillary sprouts, originating from the host microvasculature. Until day 10, these sprouts interconnected with each other to form a new microvascular network. At day 14, the inflammatory response had disappeared and the vascular ingrowth was completed. Histology confirmed the formation of granulation tissue with adequate incorporation of the mesh filaments within the host tissue. We conclude that this novel model of surgical mesh implantation is a useful experimental approach to analyze host tissue response and vascular ingrowth of newly devised materials for hernia repair.

New formation of periodontal tissues around titanium implants in a novel dentin chamber model
Parlar, A., D. D. Bosshardt, et al. (2005), Clin Oral Implants Res 16(3): 259-67.
Abstract: Direct bone-to-implant contact, defined as "osseointegration", is considered most optimal for long-term stability and survival of dental implants. However, the possibility of the formation of a tooth-like attachment apparatus around implants has also been demonstrated. The purpose of this study was to explore the formation of periodontal tissues around titanium implants using a novel and unique experimental model. After resection of the crowns of the maxillary canine teeth in nine mongrel dogs, the roots were hollowed to a depth of 5 mm leaving a thin dentinal wall. Slits were prepared in the cavity wall to create passages from the chamber to the periodontal ligament area. A custom-made, titanium implant was placed into the center of each chamber. Machined, titanium plasma sprayed (TPS) and sand blasted with large grit and acid attacked (SLA) surfaces were used. A collagen barrier was placed over the submerged chamber. Following 4 months of healing, jaw sections were processed for histology. Newly formed periodontal ligament, alveolar bone, and root cementum filled the space between the implant and the wall of the chamber. Ingrown bone was neither in contact with dentin nor with the implant. Thus, an interposed soft connective tissue layer was present. Healing by fibrous encapsulation was observed around most implants. However, cellular cementum was deposited on one TPS and one SLA implant and on the dentinal walls of the chamber. This study shows a remarkable capacity for new periodontal tissue formation at a site where no such tissues ever existed. Maintenance of original periodontal tissue domains most likely prevented osseointegration of the implants. The cementum layer deposited on two implants was likely formed through cementoconductivity rather than by differentiation of periodontal ligament cells upon contact with the implant surface.

New horizons in orthopaedics: a rational discussion of biologics and bone graft substitutes
Watson, J. T. (2005), Mo Med 102(3): 240-4.
Abstract: Numerous inductive proteins, conductive substrates, and autogenous cellular concentration techniques have become clinically available as substitutes for autogenous bone graft. This review presents a critical analysis of their preclinical and clinical efficacy. In many instances, the widespread use of these materials must be questioned based on the limited clinical data available. A thorough knowledge of these materials is crucial for the surgeon to match the material to its defined indications.

New hypothesis on the role of alternating sequences in calcium-alginate gels
Donati, I., S. Holtan, et al. (2005), Biomacromolecules 6(2): 1031-40.
Abstract: The availability of mannuronan and mannuronan C-5 epimerases allows the production of a strictly alternating mannuronate-guluronate (MG) polymer and the MG-enrichment of natural alginates, providing a powerful tool for the analysis of the role of such sequences in the calcium-alginate gel network. In view of the calcium binding properties of long alternating sequences revealed by circular dichroism studies which leads eventually to the formation of stable hydrogels, their direct involvement in the gel network is here suggested. In particular, 1H NMR results obtained from a mixed alginate sample containing three polymeric species, G blocks, M blocks, and MG blocks, without chemical linkages between the block structures, indicate for the first time the formation of mixed junctions between G and MG blocks. This is supported by the analysis of the Young's modulus of hydrogels from natural and epimerized samples obtained at low calcium concentrations. Furthermore, the "zipping" of long alternating sequences in secondary MG/MG junctions is suggested to account for the shrinking (syneresis) of alginate gels in view of its dependence on the length of the MG blocks. As a consequence, a partial network collapse, macroscopically revealed by a decrease in the Young's modulus, occurred as the calcium concentration in the gel was increased. The effect of such "secondary" junctions on the viscoelastic properties of alginate gels was evaluated measuring their creep compliance under uniaxial compression. The experimental curves, fitted by a model composed of a Maxwell and a Voigt element in series, revealed an increase in the frictional forces between network chains with increasing length of the alternating sequences. This suggests the presence of an ion mediated mechanism preventing the shear of the gel.

New ideas in biomaterials science--a path to engineered biomaterials
Bruck, S. D. and L. W. Schroeder (1994), J Biomed Mater Res 28(1): 133-6.

New ideas in biomaterials science--a path to engineered biomaterials
Ratner, B. D. (1993), J Biomed Mater Res 27(7): 837-50.
Abstract: Our existing biomaterials, although demonstrating generally satisfactory clinical performance, were developed based upon a trial-and-error optimization approach rather than being engineered to produce the desired interfacial reaction. Most biomaterials exhibit a nonspecific biological reaction, with sluggish kinetics and a broad spectrum of active processes simultaneously occurring. This article describes materials science nanotechnology, and molecular biology techniques that may permit the synthesis of precisely engineered surfaces. Such surfaces might demonstrate rapid, precise reactions with proteins and cells. This opens the question, "what type of specific surface bioreactions do we want?" New thoughts on biocompatibility are presented that may be helpful in the design of specific surfaces yielding precise, defined biological responses.

New method for preparing more stable microcapsules for the entrapment of genetically engineered cells
Wang, M. Y., Y. T. Yu, et al. (2005), Artif Cells Blood Substit Immobil Biotechnol 33(3): 257-69.
Abstract: In this paper, we studied a new preparation method of microcapsules for entrapment of genetically engineered cells. Polyvinyl alcohol microcapsules having well defined shape, high mechanical strength, good biochemical and permeability properties were prepared by using low temperature physical cross-linking method. Comparing with currently used alginate-polylysine-alginate microcapsules, polyvinyl alcohol microcapsules have much higher mechanical strength. The low temperature physical crosslinking procedure of polyvinyl alcohol is nontoxic to the genetically engineered E. coli DH5alpha cell, which attained high activity in decomposing and metabolizing urea in vitro studies.

New method to quantitate platelets adhered on biomaterials using monoclonal antibodies to human platelet membrane glycoprotein SZ-21
Xi, T. F., J. C. Zhang, et al. (1990), Biomater Artif Cells Artif Organs 18(3): 423-35.
Abstract: This study developed a new technique to quantitate platelets adhered on biomaterials surfaces in vitro, based on a surface phased radioimmunoassay using a monoclonal antibody SZ-21, directed specifically against the membrane glycoprotein complex IIIa of human platelets. In vitro perfusion is performed in system which consists of testing tubes and infusion pump. After 5 minutes perfusion with fresh ACD anticoagulated human whole blood at 2,000s-1 platelets deposition on surface precoated with proteins determined using anti-human platelet antibody (125 I-SZ-21) are 4,173 +/- 932 (Albumin), 59,032 +/- 25,554 (Fibrinogen), and 71,253 +/- 11,484 (Collagen). Meanwhile, platelets adhered on surfaces of four polymers were determined (platelet/mm2): 19,493 +/- 2,050 (Silicone), 48,193 +/- 4,055 (Polytetrafluoroethylene), 50,375 +/- 8,675 (Polyvinyl chloride) and 101,906 +/- 5,916 (Polyethylene). These results were confirmed by SEM. This method is not only applied for evaluating rapidly and reliably blood compatibility of biomaterials in vitro, but will be used at basic study for interaction of blood materials.

New methods for the generation of carbohydrate arrays on glass slides and their evaluation
Biskup, M. B., J. U. Muller, et al. (2005), Chembiochem 6(6): 1007-15.
Abstract: Glycosides, having spacers functionalized with an aldehyde or a carboxylic group, were immobilized through reductive amination or amidation, respectively, onto amino-functionalized glass slides. Hybridization experiments with lectins exhibited very little nonspecific protein binding, hence precluding the necessity for the blocking of unreacted functional groups on the glass slide. The covalency and the concentration dependency of the sugar ligation to the glass slide were demonstrated; the reversibility and the selectivity of lectin-carbohydrate interactions were shown.

New methods for the investigation of blood-biomaterial interaction
Schutt, W., U. Thomaneck, et al. (1995), Artif Organs 19(8): 847-51.
Abstract: Quantitative microscopy with integrated image processing is a useful tool for investigation of the interaction of blood components with biomaterials. We have developed new automated measuring devices suitable for simultaneously characterizing biological cells (size, shape, localization, migration, electrophoresis), synthetic particles (electrophoretic fingerprinting), and dialysis membranes (morphology, electric charge). These techniques are useful for the investigation of cell adherence on biomaterials, localization of cells in membrane filters (Chemotaxis), characterization of the protein adsorption on model systems, detection of cytokines (produced after lymphocyte-biomaterial contact), and estimation of morphological properties and charge distribution in dialysis membranes.

New nanocomposite materials reinforced with cellulose whiskers in atactic polypropylene: effect of surface and dispersion characteristics
Ljungberg, N., C. Bonini, et al. (2005), Biomacromolecules 6(5): 2732-9.
Abstract: New nanocomposite films were prepared with atactic polypropylene as the matrix and either of three types of cellulose whiskers, with various surface and dispersion characteristics, as the reinforcing phase: aggregated without surface modification, aggregated and grafted with maleated polypropylene or individualized and finely dispersed with a surfactant. Films obtained by solvent casting from toluene were investigated by means of scanning electron microscopy, dynamic mechanical analysis, and tensile testing. In the linear region, the mechanical properties above the glass-rubber transition were found to be drastically enhanced for the nanocomposites as compared to the neat polypropylene matrix. These effects were ascribed to the formation of a rigid network with filler/filler interactions. In addition, interactions between the filler and the matrix as well as the dispersion quality were found to play a major role on the mechanical properties of the composites when investigation of the films was performed in the nonlinear region.

New non-woven polyurethane-based biomaterials for the cultivation of hepatocytes: expression of differentiated functions
Gomez-Lechon, M. J., J. V. Castell, et al. (2000), J Mater Sci Mater Med 11(1): 37-41.
Abstract: A new non-woven polyetherurethane support suitable to host cultured hepatocytes has been developed. Prior to its use in bioreactors and artificial liver devices, the biocompatibility of this new material was investigated. The experiments have shown that the survival and functionality of hepatocytes entrapped in the non-woven polymer were longer than that of monolayer cultured hepatocytes, under serum-free culture conditions. Hepatic specific metabolic functions, namely, synthesis of urea and synthesis and secretion of plasma proteins, were well maintained by hepatocytes entrapped in non-woven polyetherurethane sheets. Cells also retained the expression of biotransformation activities of 7-ethoxycoumarin-O-deethylase as well as CYP2A1, CYP2B1 and CYP3A1. The results presented in this paper point to non-woven polyetherurethane sheets as a suitable biocompatible support for functional, three-dimensional hepatocyte cultures.

New polymeric biomaterials-phospholipid polymers with a biocompatible surface
Ishihara, K. (2000), Front Med Biol Eng 10(2): 83-95.
Abstract: New biomedical polymers were designed with attention to the surface of biological membranes, i.e. the surface was completely covered with phospholipid polar groups. The polymers with a phosphorylcholine group, 2-methacryloyloxyethyl phosphorylcholine (MPC) co-polymerized with hydrophobic alkyl group, could interact with phospholipids in plasma selectively and strongly. The adsorbed phospholipids on the polymer surface were concentrated, organized each other and then formed a self-assembled biomimetic membrane surface. The surface showed excellent resistance for both protein adsorption and blood cell adhesion, i.e. the MPC polymer showed good blood compatibility. Based on these characteristics of the MPC polymer, it was applied to improve the biocompatibility and biostability of an implantable glucose sensor. The relative output current of the sensor covered with the MPC polymer membrane was maintained as the initial level even after 14 days of subcutaneous implantation in a rat. Therefore, it is concluded that the MPC polymer membrane is an excellent material for implantable biomedical devices.

New porous biomaterials by replication of echinoderm skeletal microstructures
Weber, J. N., E. W. White, et al. (1971), Nature 233(5318): 337-9.

New silk protein: modification of silk protein by gene engineering for production of biomaterials
Mori, H. and M. Tsukada (2000), J Biotechnol 74(2): 95-103.
Abstract: The interest in silk fibroin morphology and structure have increased due to its attractiveness for bio-related applications. Silk fibers have been used as sutures for a long time in the surgical field, due to the biocompatibility of silk fibroin fibers with human living tissue. In addition, it has been demonstrated that silk can be used as a substrate for enzyme immobilization in biosensors. A more complete understanding of silk structure would provide the possibility to further exploit silk fibroin for a wide range of new uses, such as the production of oxygen-permeable membranes and biocompatible materials. Silk fibroin-based membranes could be utilized as soft tissue compatible polymers. Baculovirus-mediated transgenesis of the silkworm allows specific alterations in a target sequence. Homologous recombination of a foreign gene downstream from a powerful promoter, such as the fibroin promoter, would allow the constitutive production of a useful protein in the silkworm and the modification of the character of silk protein. A chimeric protein consisted of fibroin and green fluorescent protein was expressed under the control of fibroin in the posterior silk gland and the gene product was spun into the cocoon layer. This technique, gene targeting, will lead to the modification and enhancement of physicochemical properties of silk protein.

New surgical approach for root coverage of localized gingival recession with acellular dermal matrix: a 12-month comparative clinical study
Barros, R. R., A. B. Novaes, Jr., et al. (2005), J Esthet Restor Dent 17(3): 156-64; discussion 164.
Abstract: BACKGROUND: Acellular dermal matrix graft (ADMG) has been used as an advantageous substitute for autogenous subepithelial connective tissue graft (SCTG). However, the surgical techniques used were primarily developed for the SCTG, and they may not be adequate for ADMG since it has a different healing process than SCTG owing to its different vascular and cellular structures. This study compared the 1-year clinical outcome of a new surgical approach with the outcome of a conventional procedure for the treatment of localized gingival recessions, both performed using the ADMG. MATERIALS AND METHODS: The clinical parameters-probing depth, relative clinical attachment level, gingival recession (GR), and width of keratinized tissue-of 32 bilateral Miller Class I or II gingival recessions were assessed at baseline and 12 months postoperatively. RESULTS: Significant clinical changes for both surgical techniques were achieved after this period, including GR reduction from 3.4 mm presurgery to 1.2 mm at 1 year for the conventional technique and from 3.9 mm presurgery to 0.7 mm at 1 year for the new technique. The percentage of root coverage was 62.3% and 82.5% for the conventional and new techniques, respectively. Comparisons between the groups after this period by Mann-Whitney rank sum test revealed statistically significant greater reduction of GR favoring the new procedure (p =.000). CLINICAL SIGNIFICANCE: Based on the results of this study, it can be concluded that a new surgical technique using an ADMG is more suitable for root coverage when compared with the conventional technique. The results revealed a statistically significant improvement in clinical performance with the ADMG approach.

New tension band material for fixation of transverse olecranon fractures: a biomechanical study
Lalonde, J. A., Jr., R. D. Rabalais, et al. (2005), Orthopedics 28(10): 1191-4.
Abstract: This study tested the use of braided polyethylene cable as an option for repairing transverse olecranon fractures. Six cadaveric elbows underwent a transverse olecranon osteotomy followed by fixation with tension band constructs using 18-gauge wire and Secure-Strand (U.S. Surgical, North Haven, Conn). Distraction forces up to 450 N were applied to the triceps tendon while measuring fracture displacement with an extensometer. The average maximal fracture gap with the standard AO tension band technique using stainless steel wire was 0.66 +/- 0.43 mm, as opposed to 0.68 +/- 0.45 mm with braided polyethylene cable. A paired t test indicated no significant difference between the two materials. These results support the feasibility of braided polyethylene cable as an alternative to the standard steel-wire tension band.

New titanium alloys for biomaterials: a study of mechanical and corrosion properties and cytotoxicity
Kim, T. I., J. H. Han, et al. (1997), Biomed Mater Eng 7(4): 253-63.
Abstract: Three new titanium alloys with Zr, Nb, Ta, Pd and In as alloying elements were developed and compared with currently used implant metals, namely, pure Ti and Ti-6Al-4V alloy, in terms of mechanical and corrosion properties, and cytotoxicity. New alloys showed comparable mechanical properties with that of the Ti-6Al-4V alloy, but increased corrosion potential, somewhat decreased breakdown potential and increased corrosion rate. There were no significant differences in cell growth on the surface of the various metal specimens, indicating that the cells cannot differentiate between the passivated surfaces of the various Ti metals.

News in brief: challenges and directions in biomaterials research
Papadaki, M. (2004), IEEE Eng Med Biol Mag 23(5): 84, 90.

NIH Biomaterials and Medical Implant Science Coordinating Committee
Watson, J. T. (1997), Asaio J 43(4): 370.

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