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Record 2841 to 2860

Mid-term wear characteristics of an uncemented acetabular component
Goosen, J. H., C. C. Verheyen, et al. (2005), J Bone Joint Surg Br 87(11): 1475-9.
Abstract: We investigated the rate of polyethylene wear of a cementless acetabular component at different periods of follow-up in order to test the hypothesis than an irrecoverable deformation process (creep) was followed by an initially low, but gradually increasing wear rate. We studied prospectively 93 uncemented total hip arthroplasties in 83 patients (mean age 50 years (22 to 63)) with a mean follow-up of 8.2 years (3 to 12). We measured the penetration of the femoral head from radiographs taken immediately after surgery at three, six and nine years, or at the latest follow-up. The median wear rate was 0.17 mm per year in the first three years, a finding which we considered to be caused by creep. Thereafter, the rate of wear declined to 0.07 mm per year (four- to six-year period) and then increased to 0.17 mm per year (seven to nine years) and 0.27 mm per year (more than nine years), which we considered to be a reflection of genuine polyethylene wear. After the nine-year follow-up the wear rates were higher in patients with marked osteolysis. We found no relationship between the inclination angle of the acetabular component or femoral head orientation and the rate of wear. No acetabular component required revision.

Migration pattern, morphology and viability of cells suspended in or sealed with fibrin glue: a histomorphologic study
Gille, J., U. Meisner, et al. (2005), Tissue Cell 37(5): 339-48.
Abstract: INTRODUCTION: We studied the migration pattern, morphology and viability of cells suspended in five different fibrin glues. Besides this, the behaviour of chondrocytes seeded on porous matrices comprising different collagen types sealed with fibrin glue was investigated. MATERIAL AND METHODS: In an experiment A, cell suspension (0.5x10(6) cells) was incubated with different fibrin glues. Experiment B was set up to evaluate chondrocytes migration either through a collagen I/III (Chondro-Gide, Geistlich Biomaterials, Switzerland) or collagen II matrix sealed with different fibrin glues in a perfusion chamber system. Analysis were performed by lightmicroscopy (Mayer's hematoxylin-eosin; Masson-Goldner; TUNEL test) and by transmission and scanning electron microscopy. All fibrin glues were measured for TGF-beta 1 and 2 with a specific ELISA. RESULTS: After incubation of cell suspension in autologous fibrin glue, the morphology of cells is chondrocyte-like. Spindly, process-bearing cells were seen in commercial fibrin glue. Cells suspended in commercial fibrin glue revealed a significant higher percentage of TUNEL positive cells compared to fibrin tissue adhesives mixed with autologous serum (p=0.006). The TGF-beta 1 and 2 concentration was significantly higher in partial autologous fibrin sealant (PAF) compared to their commercial counterparts (p=0.001). Cells seeded on the collagen I/III matrix retained their chondrocytic morphology, while in the type II collagen matrix the chondrocytes displayed a fibroblastic phenotype. The ratio of TUNEL positive cells for the collagen I/III matrix was significantly surpassed by the values, when a collagen II matrix was used (p=0.008). No ingrowth of cells was seen in any of the experimental conditions. CONCLUSION: Partial autologous fibrin glue and collagen I/III matrices are favourable in respect to migration pattern, morphology and viability, but definitive conclusions can only be drawn after in vivo studies. This will be addressed in future animal studies.

Mineralization of synthetic polymer scaffolds: a bottom-up approach for the development of artificial bone
Song, J., V. Malathong, et al. (2005), J Am Chem Soc 127(10): 3366-72.
Abstract: The controlled integration of organic and inorganic components confers natural bone with superior mechanical properties. Bone biogenesis is thought to occur by templated mineralization of hard apatite crystals by an elastic protein scaffold, a process we sought to emulate with synthetic biomimetic hydrogel polymers. Cross-linked polymethacrylamide and polymethacrylate hydrogels were functionalized with mineral-binding ligands and used to template the formation of hydroxyapatite. Strong adhesion between the organic and inorganic materials was achieved for hydrogels functionalized with either carboxylate or hydroxy ligands. The mineral-nucleating potential of hydroxyl groups identified here broadens the design parameters for synthetic bonelike composites and suggests a potential role for hydroxylated collagen proteins in bone mineralization.

Mineralogical and geochemical characterization of arsenic in an abandoned mine tailings of Korea
Ahn, J. S., Y. S. Park, et al. (2005), Environ Geochem Health 27(2): 147-57.
Abstract: The mineralogical and chemical characteristics of As solid phases in arsenic-rich mine tailings from the Nakdong As-Bi mine in Korea was investigated. The tailings generated from the ore roasting process contained 4.36% of As whereas the concentration was up to 20.2% in some tailings from the cyanidation process for the Au extraction. Thin indurated layers and other secondary precipitates had formed at the surfaces of the tailings piles and the As contents of the hardened layers varied from 2.87 to 16.0%. Scorodite and iron arsenate (Fe3AsO7) were the primary As-bearing crystalline minerals. Others such as arsenolamprite, bernardite and titanium oxide arsenate were also found. The amorphous As-Fe phases often showed framboidal aggregates and gel type textures with desiccation cracks. Sequential extraction results also showed that 55.7-91.1% of the As in tailings were NH(4)-oxalate extractable As, further confirmed the predominance of amorphous As-Fe solid phases. When the tailings were equilibrated with de-ionized water, the solution exhibited extremely acidic conditions (pH 2.01-3.10) and high concentrations of dissolved As (up to 29.5 mg L(-1)), indicating high potentials for As to be released during rainfall events. The downstream water was affected by drainage from tailings and contained 12.7-522 microg L(-1) of As. The amorphous As-Fe phases in tailings have not entirely been stabilized through the long term natural weathering processes. To remediate the environmental harms they had caused, anthropogenic interventions to stabilize or immobilize As in the tailings pile should be explored.

Miniature fiber-optic multicavity Fabry-Perot interferometric biosensor
Zhang, Y., H. Shibru, et al. (2005), Opt Lett 30(9): 1021-3.
Abstract: A fiber-optic sensor is designed based on multicavity Fabry-Perot interferometry for the study of optical thickness in self-assembled thin-film layers. This miniature sensor is applicable not only to the measurement of self-assembled polyelectrolyte layers but also to the immobilization of proteins such as immunoglobulin G (IgG). The binding of IgG and the corresponding antigen is observed, and the nonspecific binding characteristics are investigated. The optical thickness changes are used to evaluate the immobilization of the IgG and the immunological activities of the immobilized layers.

Minimizing the surgical approach in patients with spondylitis
von Stechow, D., D. Scale, et al. (2005), Clin Orthop Relat Res 439: 61-7.
Abstract: Minimizing the surgical approach in treating patients with spinal infections by using local antibiotic treatment and avoiding a ventral approach reduces the anesthesia and surgical risks in patients with comorbidities. In this study we used calcium sulphate pellets (OsteoSet T and the OsteoSet Bone-void Filler kit) as a delivery system for different antibiotics. Of a group of 32 patients with histologically and microbiologically diagnosed spondylitis, a cohort of 16 patients was treated by just a dorsal surgical approach in combination with a local antibiotic delivery system. Of these 16 patients, 14 patients showed a normalization of the infection parameters, no more bone loss in the spondylitic region, and a bony fusion after 6 to 9 months postoperatively. Two patients died from septic circumstances 4 and 6 weeks postoperatively. Two patients had to have one revision surgery because of a seroma; no other complications caused by the calcium sulphate pellets were observed. The use of calcium sulphate pellets as antibiotic delivery system allows a controlled local antibiotic therapy with an osteoconductive material in combination with a minimized surgical approach. Furthermore, calcium sulphate pellets have proven their reliable capability as bone void filler.

Mode of action of an antimicrobial biomaterial for use in hydrocephalus shunts
Bayston, R., W. Ashraf, et al. (2004), J Antimicrob Chemother 53(5): 778-82.
Abstract: OBJECTIVES: Infection remains a major complication of shunting for hydrocephalus. The causative bacteria, mainly staphylococci, gain access to the shunt at operation and colonize the shunt tubing. This leads to biofilm development requiring shunt removal. As there is no clear evidence to support antibiotic prophylaxis, we have developed an impregnated antimicrobial shunt material. This study aimed to elucidate its mode of action in terms of bacterial adherence and killing kinetics. METHODS: Plain and impregnated material, with and without plasma protein conditioning film, were exposed to Staphylococcus epidermidis. Bacterial adherence was determined by scanning electron microscopy, chemiluminescence and culture. Time taken to kill 100% of bacteria (tK(100)) was determined by serial chemiluminescence, culture and the use of differential viability microscopy. RESULTS: The antimicrobial material did not reduce bacterial adherence. However, 100% of attached bacteria were killed in 48-52 h, even in the presence of a conditioning film. CONCLUSIONS: Impregnated antimicrobial material is likely to reduce shunt infection rates significantly without the risks and side effects of systemic antibiotics.

Model for quantitative immunohistochemical assessment of pulpal response to biomaterials
Pertot, W. J., V. Sindres, et al. (1997), J Biomed Mater Res 34(4): 457-62.
Abstract: The purpose of this study was to propose a new method for quantitative evaluation of the pulpal inflammation to restorative materials using immunohistochemistry and image analysis. Class V cavities were prepared and filled with different restorative materials in 20 healthy premolars to be extracted for orthodontic reasons. Teeth were extracted at different time intervals, fixed, demineralized, and embedded in paraffin. Six-micrometer-thick sections were cut serially and mounted on slides and every fifth section was stained using hematoxylin and eosin or Masson's trichrome, and served to localize the inflammatory reaction. The slides corresponding to the bulk of the inflammatory reaction were then used for immunohistochemical detection of the inflammatory cells using monoclonal antibodies: CD15 (granulocytes and histiocytes), CD45RO (T lymphocytes and monocytes), Pan-B cell (B lymphocytes, macrophages, and a subpopulation of T lymphocytes), CD45RA (B lymphocytes and monocytes), and EMA (plasma cells). The slides were observed and submitted to computerized image analysis using a SAMBA 2000 system for counting of the cells. The CD15, CD45RO, Pan-B-cell, and CD45RA antibodies positively stained the target cells, which could be counted with the computer. The EMA antibody did not permit staining of cells. These results indicate that polymorphonuclears, T lymphocytes, and B lymphocytes are present in inflamed human dental pulp. The immunologic detection of inflammatory cells followed by computerized image analysis allows an accurate characterization of pulpal pathology, and could be useful for the study of pulp reactions to restorative biomaterials.

Modeling of RGDC film parameters using X-ray photoelectron spectroscopy
Popat, K. C., E. E. Leary Swan, et al. (2005), Langmuir 21(16): 7061-5.
Abstract: Immobilization of peptides on surfaces is a common method to investigate biological response to biomaterials for the development of improved tissue engineering constructs. Peptide immobilization can be achieved by either physical adsorption or covalent attachment on the surface. In this work, the RGDC peptide was covalently immobilized to alumina substrate for investigation of bone cell response. An understanding of RGDC film formation is necessary for further biological characterization. Thus, X-ray photoelectron spectroscopy was used to chemically characterize these films. These data were further utilized to calculate RGDC film thickness, density, and coverage, which are essential for understanding bone cell interactions with the underlying films and substrate.

Modeling small-molecule release from PLG microspheres: effects of polymer degradation and nonuniform drug distribution
Raman, C., C. Berkland, et al. (2005), J Control Release 103(1): 149-58.
Abstract: Modeling release of small molecules from degradable microspheres is important to the design of controlled-release drug delivery systems. Release of small molecules from poly(d,l-lactide-co-glycolide) (PLG) particles is often controlled by diffusion of the drug through the polymer and by polymer degradation. In this study, a model is developed to independently determine the contributions of each of these factors by fitting the release of piroxicam from monodisperse 50-microm microspheres made with PLG of different initial molecular weights. The dependence of the drug diffusivity on polymer molecular weight was determined from in vitro release of piroxicam from monodisperse 10-microm PLG microspheres, and the polymer degradation rate was experimentally measured using gel permeation chromatography. The model also incorporates the effect of nonuniform drug distribution within the microspheres, which is obtained from confocal fluorescence microscopy. The model results agree well with experiments despite using only one fit parameter.

Modeling surfactant adsorption on hydrophobic surfaces
Nielsen, S. O., G. Srinivas, et al. (2005), Phys Rev Lett 94(22): 228301.
Abstract: Surfactant adsorption on hydrophobic surfaces is of current interest in attempts to solubilize single-wall carbon nanotubes and to render quantum dots biocompatible. A coarse grained method is presented for incorporating a hydrophobic surface into existing liquid force fields by appealing to statistical mechanics and probability theory. The dimensionality problem which arises is overcome with an approximate treatment and the entire procedure is applied to aqueous n-alkyl poly(ethylene oxide) adsorbing onto a graphite surface. The simulations are in excellent agreement with atomic force microscopy data. The mechanism of micelle adsorption onto a partially coated surface is reported for the first time and has implications for the construction of nanotemplates.

Modern biomaterials advance the ancient art of dentistry
Szycher, M. and R. S. Baratz (1987), J Biomater Appl 1(3): 307-15.

Modification of biomaterials to improve blood compatibility
Bamford, C. H., I. P. Middleton, et al. (1992), Int J Artif Organs 15(2): 71-8.

Modification of carbon-coated TiO2 by iron to increase adsorptivity and photoactivity for phenol
Tryba, B., M. Toyoda, et al. (2005), Chemosphere 60(4): 477-84.
Abstract: Carbon-coated TiO(2) modified by iron, were prepared from TiO(2) of anatase structure and PET modified by FeC(2)O(4). Catalysts were prepared by mixing powders of TiO(2) and modified PET and heating at different temperatures, from 400 to 800 degrees C under flow of Ar gas. High adsorption of phenol was observed on the catalyst heated at 400 degrees C, confirmed by FT-IR analysis. On this catalyst, fast rate of phenol decomposition was achieved by addition of small amount of H(2)O(2) to the reaction mixture. Phenol decomposition proceeded mainly through the direct oxidation of phenol species adsorbed on the catalyst surface due to the photo-Fenton reaction. Iron-modified carbon-coated TiO(2) catalysts heated at 500-800 degrees C showed almost no phenol adsorption or oxidation.

Modification of human platelet adhesion on biomaterial surfaces by protein preadsorption under static and flow conditions
Otto, M., A. Franzen, et al. (2004), J Mater Sci Mater Med 15(1): 35-42.
Abstract: Biomaterial-induced thrombosis remains one of the main complications of vascular implant devices. Preadsorbed proteins on the biomaterial/blood interface will modify the adhesion and activation of platelets (PTLs) during the initial contact-phase. Our results clearly show that PTL-adherence on biomaterials is influenced not only by protein preadsorption, but also by flow conditions. The covalent coating of TCPS and glass by phosphorylcholine (PC) induces a significant decrease of PTL adhesion but leads to a slight, but nevertheless significant activation of PTL, which was detected by the induction of P-selectin expression using FACS analysis. Methodologically, the visualization of PTL adhesion gave more reliable results for measurement of PTL adhesion than the cell-enzyme immunoassay (EIA) for P-selectin. Human citrated plasma caused an inhibition of PTL. It is probable, that the contained sodium citrate may inhibit PTL adhesion by its calcium ion-binding capacity. The flow experiment as dynamic system is in our view absolutely essential for the evaluation of biomaterials for vascular prosthesis, and is in accordance with the international standards. The results of the experiments also suggest that investigations under static and flow conditions are needed to determine the influence of protein adsorption on mixed blood cell populations, for example, on PTL and PMN mixtures/co-cultures in order to achieve a better simulation of the in vivo situation.

Modification of human polymorphonuclear neutrophilic cell (PMN)-adhesion on biomaterial surfaces by protein preadsorption under static and flow conditions
Otto, M., B. Wahn, et al. (2003), J Mater Sci Mater Med 14(3): 263-70.
Abstract: Biomaterials induce a specific reaction after implantation in the human body. This reaction depends on the chemical and physico-chemical properties of the material as well as on the site and type of implantation. We have used a dynamic model, the parallel-plate flow-chamber, to examine the interactions of different biomaterials with polymorphonuclear neutrophilic cell (PMN) and how these interactions are influenced by protein preadsorption. Our results clearly show that for hydrophobic materials, glass and PE, which induce a prominent adhesion of PMN, the mixture of albumin and fibrinogen induces the best inhibitory effect. On hydrophilic biomaterial surfaces, untreated TCPS and PC-coated TCPS, reveal only a minor influence of adsorbed proteins on PMN adhesion because of a primary low adhesive surface for PMN and proteins as well. Human citrated plasma leads only to a slight inhibition of PMN adhesion. On the hydrophobic materials, glass and PE, bovine serum albumin (BSA) had the best anti-adhesive potential with respect to PMN. The coating using phosphorylcholine is an excellent surface modification to prevent PMN-adhesion and protein adsorption. The results of our experiments suggest that investigations under static and flow conditions are also needed to determine the influence of protein adsorption on other relevant blood cell populations, for example, platelets and monocytes.

Modification of jute fibers with polystyrene via atom transfer radical polymerization
Plackett, D., K. Jankova, et al. (2005), Biomacromolecules 6(5): 2474-84.
Abstract: Atom transfer radical polymerization (ATRP) was investigated as a method of covalently bonding polystyrene to jute (Corchorus capsularis) and as a possible approach to fiber composites with enhanced properties. Jute fibers were modified with a brominated initiator and subsequently ATRP modified to attach polystyrene and then examined using SEM, DSC, TGA, FTIR, XPS, elemental analysis, and Py-GC-MS. These techniques confirmed that polystyrene had been covalently bound to the fibers and consequently ATRP-modified jute fiber mats were used to prepare hot-pressed polystyrene composites. Composite specimens were tensile tested and fracture surfaces examined using SEM. Although SEM examination suggested different fracture modes between unmodified fiber and ATRP-modified samples, the tensile strength of modified samples was slightly lower on average than that of unmodified samples. For fiber composite applications, we conclude that further optimization of the ATRP method is required, possibly targeting higher and more uniform loading of polystyrene on the fibers.

Modification of surface properties of biomaterials influences the ability of Candida albicans to form biofilms
Chandra, J., J. D. Patel, et al. (2005), Appl Environ Microbiol 71(12): 8795-801.
Abstract: Candida albicans biofilms form on indwelling medical devices (e.g., denture acrylic or intravenous catheters) and are associated with both oral and invasive candidiasis. Here, we determined whether surface modifications of polyetherurethane (Elasthane 80A [E80A]), polycarbonateurethane, and poly(ethyleneterephthalate) (PET) can influence fungal biofilm formation. Polyurethanes were modified by adding 6% polyethylene oxide (6PEO), 6% fluorocarbon, or silicone, while the PET surface was modified to generate hydrophilic, hydrophobic, cationic, or anionic surfaces. Formation of biofilm was quantified by determining metabolic activity and total biomass (dry weight), while its architecture was analyzed by confocal scanning laser microscopy (CSLM). The metabolic activity of biofilm formed by C. albicans on 6PEO-E80A was significantly reduced (by 78%) compared to that of biofilm formed on the nonmodified E80A (optical densities of 0.054 +/- 0.020 and 0.24 +/- 0.10, respectively; P = 0.037). The total biomass of Candida biofilm formed on 6PEO-E80A was 74% lower than that on the nonmodified E80A surface (0.46 +/- 0.15 versus 1.76 +/- 0.32 mg, respectively; P = 0.003). Fungal cells were easily detached from the 6PEO-E80A surface, and we were unable to detect C. albicans biofilm on this surface by CSLM. All other surface modifications allowed formation of C. albicans biofilm, with some differences in thearchitecture. Correlation between contact angle and biofilm formation was observed for polyetherurethane substrates (r = 0.88) but not for PET biomaterials (r = -0.40). This study illustrates that surface modification is a viable approach for identifying surfaces that have antibiofilm characteristics. Investigations into the clinical utility of the identified surfaces are warranted.

Modification of the influence of biomaterials on contact activation
Sundaram, S., L. Irvine, et al. (1991), Int J Artif Organs 14(11): 729-31.
Abstract: Knowledge of the influence of biomaterials on the contact phase activation of blood is important. Consequently, it is important to examine if the biomaterial influence is modified by the action of anticoagulants. Contact activation was determined by measuring FXII activity (FXIIA) by a chromogenic substrate assay. Cuprophan in the absence of anticoagulants and in the presence of heparin, low molecular weight heparin (LMWH) and hirudin was compared with controls. The controls were a polystyrene incubation test cell (PS) and two polyamide membranes, NR (zeta potential -28.6 mv and NRZ (zeta potential--18.0 mv). The investigation has confirmed that measurement of FXIIA is material dependent and demonstrated that contact activation can be mediated by antithrombotic agent.

Modifications on collagen structures promoted by 1,4-dioxane improve thermal and biological properties of bovine pericardium as a biomaterial
Forti, F. L., G. Goissis, et al. (2006), J Biomater Appl 20(3): 267-85.
Abstract: Collagen is a widely used raw material for biomaterial manufacture, which generally depends on chemical modifications of this fibrillar protein with cross-linking agents to improve biocompatibility and mechanical properties. However, cross-linking reduces the natural properties of collagen, such as low immune response, low toxicity as well as the ability to promote cellular growth and attachment. In this work, the modifications promoted by 1,4-dioxane solvent on the collagen present in native bovine pericardium (NBP) matrix routinely used in bioprosthesis manufacture, with or without subsequent cross-linking by glutaraldehyde, has been studied. The structural changes of NBP evaluated by scanning electron microscopy show that 1,4-dioxane induces a more homogeneous material by increasing aggregation of collagen fibers, while transmission scanning electron microscopy shows that natural collagen fibril arrangement, integrity, and the D-periodicity pattern are maintained by solvent treatments. Measurements of thermal stability and resistance to collagenase enzymatic digestion of NBP matrices treated with 1,4-dioxane show an increase in melting temperature and decrease in biodegradability, as compared to native pericardium. Cross-linking with glutaraldehyde improves all the analyzed NBP properties, which are not impaired by previous treatment with 1,4-dioxane. Histological evaluation of NBP submitted to 1,4-dioxane treatment shows lower lipid and cell contents and improvement in other morphologic characteristics compared to native pericardium. Altogether, these results suggest the use of 1,4-dioxane organic solvent as an alternative non-cross-linking treatment for direct utilization on rich collagen matrices, resulting in materials with improved biocompatibility and physicochemical properties suitable for tissue engineering.

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