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Sequential polyurethane-poly(methylmethacrylate) interpenetrating polymer networks as ureteral biomaterials: mechanical properties and comparative resistance to urinary encrustation
Jones, D. S., M. C. Bonner, et al. (1997), J Mater Sci Mater Med 8(11): 713-7.
Abstract: The mechanical properties and resistance to urinary encrustation of sequential-interpenetrating polymer networks (IPNs) composed of polyurethane (PU) and polymethylmethacrylate (PMMA), have been described. Mechanical properties were determined using tensile testing and dynamic mechanical analysis, whereas resistance to encrustation was examined using an in vitro model for encrustation simulating in vivo encrustation. Maximum and minimum tensile strength at break, Young's modulus, storage and loss moduli were associated with PMMA and PU, respectively. IPNs demonstrated intermediate mechanical properties which were dependent on the concentrations of the component polymers. Conversely, maximum elongation at break was observed for PU and this parameter decreased as the concentration of PMMA increased in the IPN. The dynamic mechanical damping parameter, tan delta, was similar for all IPNs at 37 degrees C. Increased advancing and decreased receding contact angles were observed for IPNs in comparison with the native PU. The rate and extent of encrustation, measured as the percentage surface coverage, was similar for PU, IPNs and PMMA. In contrast, encrustation on polyhydroxyethylmethacrylate, a model hydrogel, was greater than observed for the IPNs or component polymers. No apparent correlation was observed between the rate and/or extent of encrustation and polymer contact angle. It is concluded that these IPNs may be of clinical benefit in patients providing stent resistance to extrinsic compression of the ureter in comparison with native PU. The comparable resistance to encrustation between the IPNs and PU indicates that the use of IPNs should not be restricted in this regard.

Serum deprivation improves seeding and repopulation of acellular matrices with valvular interstitial cells
Cushing, M. C., M. P. Jaeggli, et al. (2005), J Biomed Mater Res A 75(1): 232-41.
Abstract: Cell-extracted valvular tissues (acellular scaffolds, or aScaffolds) offer unique advantages over synthetic polymers for cardiac valve engineering applications in that they retain extracellular matrix molecules to support cellular ingrowth. The extracellular matrix is important in directing many cellular pathways, such as adhesion, proliferation, migration, differentiation, and survival. However, repopulating this type of scaffold often requires high seeding densities or recurrent cell delivery. The optimization of valvular interstitial cell (VIC) seeding onto aScaffolds is reported herein. VICs (the most prevalent cell type in valve leaflets) have maximal growth in 15-20% serum concentrations on tissue-culture polystyrene. Interestingly, after VIC seeding onto aScaffolds, a reduction of serum content, from 15% serum to 5% or less, was found to increase significantly the number of adherent cells, as well as induce transfer of VICs from a tissue-culture polystyrene surface to the aScaffold. aScaffolds seeded and cultured with periods of reduced serum levels were shown to support and enhance VIC viability and attachment, as well as accelerate VIC migration into the aScaffold, leading to a uniformly repopulated valve leaflet construct after 4 weeks of static culture.

Seventh World Biomaterials Congress. 17-21 May 2004, Sydney Convention and Exhibition Centre, Darling Harbour, Sydney, Australia
Joyce, T. J. (2004), Expert Rev Med Devices 1(1): 7-9.

Shape and orientation of osteoblast-like cells (Saos-2) are influenced by collagen fibers in xenogenic bone biomaterial
Basle, M. F., F. Grizon, et al. (1998), J Biomed Mater Res 40(3): 350-7.
Abstract: The surface topography of a substratum has been shown to influence the growth and morphology of cells in culture. In this study, human osteoblast-like cells (Saos-2) were cultured on two types of xenogenic biomaterials obtained from bovine bone. Both biomaterials were similar in architectural organization and surface topography, but they differed in matrix components. The first one was characterized by preservation of the mineralized collagen matrix, and the second by complete deproteinization which only preserved the mineral phase. Cells cultured at the surface of both biomaterials were observed using scanning electron microscopy. The beta 1-integrin subunit, known to bind cell and collagen, is the major integrin of the osteoblast. It was localized using immunogold in transmission electron microscopy. At the surface of the collagen-containing matrix, cells exhibited an elongated shape and oriented axis parallel to the underlying collagen bundles. The beta 1-integrin subunit was localized at the outer surface of cells, in close association with collagen and at the contact points between cells and biomaterials. In contrast, at the surface of the single mineral matrix, cells were round shaped with random disposition. Gold particles were found around the cells with no specific relation to the biomaterial. These results strongly suggest that the chemical nature of the surface of a bone biomaterial directly influences adhesion process, shape, and spatial organization of cultured osteoblastic cells.

Shape memory alloy clip for compression colonic anastomosis
Song, C., T. Frank, et al. (2005), J Biomech Eng 127(2): 351-4.
Abstract: This study was setup to investigate the design and performance of a shape memory alloy clip for colonic anastomosis. The thermo-mechanical properties of the shape memory alloy material were studied and the data were used to derive a nonlinear material model. This enabled the development of computer computer aided design models and finite element analysis of the clip and tissue compression. The maximum strain of the anastomosis clip was within the recoverable range, and it exerted parallel compression of the colonic walls with a uniform pressure distribution. The design of the anastomosis clip was optimized for safe, simple, and effective use in colon surgery.

Shear bond strength of adhesive systems to enamel and dentin. Thermocycling influence
Dos Santos, P. A., P. P. Garcia, et al. (2005), J Mater Sci Mater Med 16(8): 727-32.
Abstract: OBJECTIVES: The purpose of the this study was to evaluate the influence of thermocycling on shear bond strength on bovine enamel and dentin surfaces of different adhesive systems. METHODS: Thirty sound bovine incisors were sectioned in mesiodistal and inciso-cervical direction obtaining 60 incisal surfaces (enamel) and 60 cervical surfaces (dentin). Specimens were randomly assigned to 3 groups of equal size (n=40), according to the adhesive system used: I-Single Bond; II-Prime & Bond NT/NRC; III-One Coat Bond. After 24-h storage in distilled water at 37 degrees C, each main group was divided into two subgroups: A-specimens tested after 24 h storage in distilled water at 37 degrees C; B-specimens submitted to thermocycling (500 cycles). Shear bond strength tests were performed. Data were submitted to ANOVA and Tukey test. RESULTS: Means (MPa) of different groups were: I-AE-16.96, AD-17.46; BE-21.60, BD-12.79; II-AE-17.20, AD-11.93; BE-20.67, BD-13.94; III-AE-25.66, AD-17.53; BE-24.20, BD-19.38. SIGNIFICANCE: Thermocycling did not influence significantly the shear bond strength of the tested adhesive systems; enamel was the dental substrate that showed larger adhesive strength; One Coat Bond system showed the best adhesive strength averages regardless of substrate or thermocycling.

Shear creep of injectable collagen biomaterials
Wallace, D. G., W. Rhee, et al. (1987), J Biomed Mater Res 21(7): 861-80.
Abstract: Shear creep experiments in a parallel-plate apparatus were carried out on two injectable forms of collagen: semidilute nonfibrillar solutions (32 and 45 mg protein/mL) and aqueous fibrillar suspensions (at 35 and 65 mg/mL). Nonfibrillar solutions were more easily deformed than fibrillar suspensions, and both materials continued to deform slowly, even at long times (up to 6 X 10(4) sec). When the creep compliance, J(t), was plotted versus t1/3, regions of linear dependence were identified, which indicated that the materials were undergoing Andrade creep. At higher stress levels, J(t) diverged from t1/3, and true viscous flow occurred. A delayed viscosity could be calculated which agreed with viscosities derived from measurements under conditions of steady shear Couette flow. The time of onset of viscous flow was identified with a specific strain for each material, suggesting yield strain behavior. An analysis of recovery curves showed that at low stress levels or for short experimental times, the Boltzmann superposition was approximately obeyed, indicating linear behavior. At high stress levels and times greater than 10(3) sec, both nonfibrillar solutions and fibrillar suspensions showed marked curvature of stress-strain curves, which indicated that the materials are nonlinear in creep.

Sheep, pig, and human platelet-material interactions with model cardiovascular biomaterials
Goodman, S. L. (1999), J Biomed Mater Res 45(3): 240-50.
Abstract: The relationship between cardiovascular device performance in animals and humans is not straightforward. As the principal formed element in a thrombus, platelets play a major role in determining the hemocompatibility of mechanical heart valves and other high-shear-rate cardiovascular devices. Since larger animals are required to test many such devices, sheep and porcine platelet responses were compared to humans. Adhesion, spreading, and the formation of thrombilike structures were examined in vitro on pyrolytic carbon mechanical heart valve leaflets, National Institutes of Health-reference polyethylene and silicone rubber, and Formvar. Principal findings were that platelet responses are strongly dependent upon the biomaterial and the species: Porcine and human platelets spread extensively on pyrolytic carbon, formed thrombuslike structures on Formvar, and were least active on silicone rubber. Human and porcine platelets responded differently to polyethylene: Human platelets spread extensively, while porcine platelets remained pseudopodial. In contrast, sheep platelets attached much less, never reached fully spread shapes, and were far less active overall. Since porcine responses were generally similar to humans, pigs may be a useful predictor of in vivo platelet-biomaterial interaction in humans. Conversely, as ovine platelets were much less active, this must be accounted for in the evaluation of cardiovascular devices tested in sheep.

Short-term effects of mineral particle sizes on cellular degradation activity after implantation of injectable calcium phosphate biomaterials and the consequences for bone substitution
Gauthier, O., J. M. Bouler, et al. (1999), Bone 25(2 Suppl): 71S-74S.
Abstract: This in vivo study investigated the influence of two calcium phosphate particle sizes (40-80 microm and 200-500 microm) on the cellular degradation activity associated with the bone substitution process of two injectable bone substitutes (IBS). The tested biomaterials were obtained by associating a biphasic calcium phosphate (BCP) ceramic mineral phase and a 3% aqueous solution of a cellulosic polymer (hydroxypropylmethylcellulose). Both were injected into osseous defects at the distal end of rabbit femurs for 2- and 3-week periods. Quantitative results for tartrate-resistant acid phosphatase (TRAP) cellular activity, new bone formation, and ceramic resorption were studied for statistical purposes. Positive TRAP-stained degradation cells were significantly more numerous for IBS 40-80 than IBS 200-500, regardless of implantation time. BCP degradation was quite marked during the first 2 weeks for IBS 40-80, and bone colonization occurred more extensively for IBS 40-80 than for IBS 200-500. The resorption-bone substitution process occurred earlier and faster for IBS 40-80 than IBS 200-500. Both tested IBS displayed similar biological efficiency, with conserved in vivo bioactivity and bone-filling ability. Differences in calcium phosphate particle sizes influenced cellular degradation activity and ceramic resorption but were compatible with efficient bone substitution.

Short-term outcome of intracranial aneurysms treated with polyglycolic acid/lactide copolymer-coated coils compared to historical controls treated with bare platinum coils: a single-center experience
Kang, H. S., M. H. Han, et al. (2005), AJNR Am J Neuroradiol 26(8): 1921-8.
Abstract: BACKGROUND AND PURPOSE: Aneurysm recanalization is an innate problem in endovascular treatment of aneurysms with coils. A coated coil system, covered with a bioabsorbable polymeric material (polyglycolic acid/lactide copolymer, PGLA), was developed to accelerate intra-aneurysmal clot organization and fibrosis. The purpose of this study was to evaluate the efficacy and safety of the PGLA-coated coils in patients with intracranial aneurysms and to compare the outcome with that of bare platinum coils. PATIENTS AND TECHNIQUES: Fifty-one patients harboring 56 intracranial aneurysms underwent endovascular embolization with the PGLA-coated coils. In the control group were 78 consecutive patients, harboring 87 aneurysms, who underwent coil embolization with bare platinum coils. The authors compared coil volume, packing attenuation, degree of occlusion of aneurysms, procedure-related complications, and follow-up results between the 2 groups. RESULTS: The PGLA-coil group showed comparable data regarding rate of total or near-total occlusion of the aneurysm, incidence procedure-related thromboembolism, and management outcome. Mean coil volume deployed and packing attenuation of the PGLA-coil group were significantly higher than those of the bare-coil group (P =.0026 and P <.0001, respectively). Radiologic follow-up evaluation revealed recanalization in 14 of 39 aneurysms (major recanalization in 5 [13%] and minor recanalization in 9 [23%]) among the PGLA-coil group and in 29 of 64 aneurysms (major recanalization in 9 [14%] and minor recanalization in 20 [31%]) among the bare-coil group. CONCLUSION: In this study, the incidence of recanalization was not different in aneurysms treated with PGLA-coated coils compared with historical controls treated with bare platinum coils.

Short-term results of the Ascension pyrolytic carbon metacarpophalangeal joint replacement arthroplasty for osteoarthritis
Nunez, V. A. and N. D. Citron (2005), Chir Main 24(3-4): 161-4.
Abstract: INTRODUCTION: Osteoarthritis of the metacarpophalangeal joints is difficult to manage due to the high demands placed on any prosthesis. We report the preliminary results of our experience using the Ascension pyrolytic carbon implant. METHOD: A pyrocarbon metacarpophalangeal joint replacement was implanted into seven patients (10 metacarpophalangeal joints) with osteoarthritis. Patients were reviewed both clinically and radiologically. RESULTS: At a mean follow-up of 2.2 years (1-4 years) there were no implant failures nor loosenings. Pain scores improved from 68% to 3% postoperatively, and there was a very high rate of patient satisfaction. CONCLUSION: Pyrocarbon implants are a promising solution to a condition which may be otherwise difficult to treat surgically.

Side effects from polydioxanone
Della Torre, F., E. Della Torre, et al. (2005), Allerg Immunol (Paris) 37(2): 47-8.
Abstract: It is the first case reported of delay hypersensitivity due to polydioxanone (PDS II).

Significance of the type and the size of biomaterial particles on phagocytosis and tissue distribution
Tomazic-Jezic, V. J., K. Merritt, et al. (2001), J Biomed Mater Res 55(4): 523-9.
Abstract: Particulates generated by dissolution or wear of injected or implanted biomaterials may migrate into various tissues and lead to activation of the host's inflammatory and immune responses. The purpose of this study was to evaluate the relevance of size and chemical composition of biomaterial particles on the pattern of particle distribution in host tissues. Adult female B6C3F1 mice were injected intraperitoneally with polymethylmethacrylate (PMMA) particles (size 1.4 and 6.4 micro in diameter) and polystyrene (PS) particles (size 1.2, 5.2, and 12.5 micro in diameter), and euthanized 1, 7, and 28 days later. Peritoneal exudate cells (PECs) were collected and the number of cells and percentage of actively phagocytic cells was determined. Macroscopic examination of the tissues in the peritoneal cavity peritoneum revealed visible accumulations of the colored PS particles in the adipose tissues adjacent to the spleen and pancreas, and caudal to the stomach. Distribution of the PS particles appeared similar regardless of the particle size. The location of PMMA particles, which were not colored, could not be distinguished from host tissue and could not be observed in this manner. Intensive phagocytosis of the small and medium sized particles by peritoneal macrophages was observed on day 1, and was diminishing by day 7 after injection. The largest PS particles (12.5 micro) were not engulfed by the peritoneal macrophages. Histological examination of the spleen, lymph nodes, and the adjacent adipose tissues revealed a marked difference in the deposition patterns of the two polymers used. PS particles, regardless of size, were accumulated primarily in the white adipose tissues adjacent to the spleen and pancreas gland, but very few particles were observed in the splenic tissue. On the other hand, mice injected with PMMA particles of either size had enlarged and activated spleens with marked deposits of particles in the red pulp. These results indicate that these PS and PMMA particles induce different patterns and intensities of the host response. The chemical makeup of the particle is more important in the distribution pattern than is the size of the particle.

Silica-coated nanocomposites of magnetic nanoparticles and quantum dots
Yi, D. K., S. T. Selvan, et al. (2005), J Am Chem Soc 127(14): 4990-1.

Silicone oil adhesion to intraocular lenses: an experimental study comparing various biomaterials
Apple, D. J., R. T. Isaacs, et al. (1997), J Cataract Refract Surg 23(4): 536-44.
Abstract: PURPOSE: To perform an in vitro experimental study comparing the degree of adherence of silicone oil to various rigid and foldable intraocular lens (IOL) designs and to the human lens capsule. SETTING: Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Seven IOL styles comprising various biomaterials were studied: fluorine-treated (Fluorlens), heparin-surface-modified (HSM), hydrogel, Memory-Lens, Poly(methyl methacrylate) (PMMA), soft acrylic, and silicone lenses; the human crystalline lens was also studied. Each lens was immersed in silicone oil for 12 hours, than photographed, studied by scanning electron microscopy (except the crystalline lens), and subjected to computer-generated image analysis to determine the silicone oil coverage. RESULTS: Silicone oil coverage of dry silicone lenses was 100% and of lenses immersed in normal saline, 82.5%. The least coverage was on the heparin-surface-modified lens (mean score 9.4%). Coverage of the other four lenses ranged from approximately 15.1% to 33.7%. Mean coverage of the human lens capsule was 10.9%. CONCLUSION: Although a silicone IOL shows maximal adherence to silicone oil, other lens biomaterials are not immune to this complication. Silicone oil coverage was related to the dispersive energy component of the surface charge of the IOL biomaterial. Low dispersive energy materials had less silicone oil coverage, while those with higher dispersive energy had more oil coverage.

Silicone rubber and natural rubber as biomaterials
Courtney, J. M. and T. Gilchrist (1980), Med Biol Eng Comput 18(4): 538-40.

Silicone rubber-hydrogel composites as polymeric biomaterials. I. Biological properties of the silicone rubber-p(HEMA) composite
Cifkova, I., P. Lopour, et al. (1990), Biomaterials 11(6): 393-6.
Abstract: A composite material was prepared consisting of silicone rubber matrix and particulate lightly cross-linked poly(2-hydroxyethyl methacrylate) (p(HEMA] hydrogel. The material resembling common silicone rubber is hydrophilic and swells in water like hydrogels. The effects of the implanted composite on tissues of the living organism were tested in rats by methods assessing local acute and chronic inflammatory reactions and calcification by means of radioactive indicators and by histological examination. Results of a 6 month implant study indicated no difference in reactions of the animal body on the silicone rubber-p(HEMA) composite and a non-toxic, non-irritant pure solid p(HEMA) control.

Silicone rubber-hydrogel composites as polymeric biomaterials. II. Hydrophilicity and permeability to water-soluble low-molecular-weight compounds
Lopour, P., P. Vondracek, et al. (1990), Biomaterials 11(6): 397-402.
Abstract: The surface and transport properties of water-swollen silicone rubber-hydrogel composites were investigated. Surface wettability of these materials, composed of a polysiloxane matrix and the hydrogel phase consisting of very fine particles of lightly cross-linked poly(2-hydroxyethylmethacrylate), increased markedly with increasing content of the hydrogel phase. For composite materials containing a lightly cross-linked 2-hydroxyethylmethacrylate (HEMA)-methacrylic acid (MAA) copolymer and polymethacrylic acid (PMAA) as the hydrogel phase, permeability to water-soluble organic compounds and drugs were measured. The permeability varied within a broad range depending on the composition and content of the hydrogel phase. High permeation rates could be obtained while still retaining relatively fair mechanical properties. Relationships between the composition of silicone rubber-hydrogel composites, their structure and the permeation coefficients of the individual permeates are discussed.

Silicone rubber-hydrogel composites as polymeric biomaterials. III. An investigation of phase distribution by scanning electron microscopy
Lednicky, F., V. Janatova, et al. (1991), Biomaterials 12(9): 848-52.
Abstract: The structure of silicone rubber-hydrogel composite materials was investigated by scanning electron microscopy (SEM) and light microscopy. The polymer phases in these materials composed of the polysiloxane matrix and very small particles of lightly cross-linked poly(2-hydroxyethylmethacrylate) or poly(2-hydroxyethylmethacrylate-co-methacrylic acid) were visualized using both methods. The distribution of polymer phases was studied by SEM of fracture surfaces of the materials. The results are discussed in relation to the transport properties of the materials.

Silicone rubber-hydrogel composites as polymeric biomaterials. IV. Silicone matrix-hydrogel filler interaction and mechanical properties
Lopour, P., Z. Plichta, et al. (1993), Biomaterials 14(14): 1051-5.
Abstract: Composite materials consisting of a silicone rubber matrix and particulate synthetic hydrogels were prepared and their mechanical properties were studied. The influence of the size, shape, aggregation of hydrogel particles, chemical reactions of polymer phases on tensile properties and tear strength of the composite materials were investigated. The relations between the properties, structure and chemical composition of polymer phases of the composite materials and their mechanical properties are discussed.

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