|Articles about Biomaterials|
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| A novel osteotropic biomaterial OG-PLG: in vitro efficacy
Whang, K., E. Grageda, et al. (2005), J Biomed Mater Res A 74(2): 247-53.
Abstract: Previously, a novel osteotropic biomaterial, OG-PLG [simvastatin grafted to poly(lactide-co-glycolide), PLG], was synthesized and shown to have degradation-controlled release kinetics. The objective here was to determine the effect of grafting statins to PLG on bone regeneration in vitro. Rat bone marrow cells were stimulated in vitro with simvastatin dissolved in media, saponified simvastatin dissolved in media, simvastatin released through diffusion from emulsion freeze-dried scaffolds, and OG-PLG. Unstimulated cultures and cultures stimulated with dexamethasone were used as negative and positive controls, respectively. In vitro bone formation was assessed using the alkaline phosphatase (ALP) and von Kossa assays at different times up to 16 days. ALP analysis revealed that saponified simvastatin at 10(-7)M and OG-PLG significantly increased ALP expression at various time points. von Kossa assay showed that simvastatin, saponified simvastatin, and OG-PLG significantly enhanced mineralization, with the effect from OG-PLG being the most significant. In short, OG-PLG significantly enhanced in vitro bone cell mineralization beyond the effect of simvastatin or saponified simvastatin dissolved in media and simvastatin released via diffusion from scaffolds.
| A novel osteotropic biomaterial OG-PLG: Synthesis and in vitro release
Whang, K., J. McDonald, et al. (2005), J Biomed Mater Res A 74(2): 237-46.
Abstract: Statins (e.g., simvastatin) have shown to induce expression of the bone morphogenic protein-2 gene in bone cells, but they are not used clinically because of a lack of a suitable delivery device. The overall objective is to develop optimized statin delivery devices for bone regeneration. The specific objective was to determine the effect of grafting statins to biodegradable poly[lactide-co-glycolide] (PLG) on release kinetics. Simvastatin was grafted to PLG (OG-PLG) and characterized using contact-angle measurements, attenuated total reflectance-Fourier transform infrared, and ultraviolet-visible spectroscopy to determine success of the synthesis. An ultraviolet-visible assay for measuring release of statins and degraded OG-PLG in media was also developed. In vitro release studies using films and scaffolds made with PLG, PLG blended with simvastatin (PLG + Sim), and OG-PLG (simvastatin grafted to PLG) blended into PLG at different concentrations showed that release rate of OG-PLG from films was significantly greater than that of PLG + Sim. However, release rate from scaffolds showed PLG + Sim to be significantly higher than that of OG-PLG. The diffusion-controlled release kinetics of simvastatin from PLG + Sim seems to be more heavily affected by device morphology, whereas the degradation-controlled release kinetics seem to be less affected. In short, release kinetics can be modulated by grafting statins to PLG.
| A novel porous Ti6Al4V: characterization and cell attachment
Li, J. P., S. H. Li, et al. (2005), J Biomed Mater Res A 73(2): 223-33.
Abstract: For the first time, a highly porous strong Ti6Al4V was produced by using a "polymeric sponge replication" method. A polymeric sponge, impregnated with a Ti6Al4V slurry prepared from Ti6Al4V powders and binders, was subjected to drying and pyrolyzing to remove the polymeric sponge and binders. After sintering at a high temperature and under high vacuum, a porous Ti6Al4V was produced. Optical microscopical observation, environmental scanning electron microscopy observation (with energy-dispersive micro X-ray analysis), mechanical tests, and metallurgical analyses were performed on the obtained porous Ti6Al4V with regard to the porous structure (both macropores and micropores), mechanical properties, chemical composition, phase compositions, and cell attachment behavior. The porous Ti6Al4V made by this method had a three-dimensional trabecular porous structure with interconnected pores mainly ranging from 400 to 700 microm and a total porosity of about 90%. The compressive strength was 10.3 +/- 3.3 MPa and the elastic constant 0.8 +/- 0.3 GPa. MC3T3-E1 cells attached and spread well in the inner surface of pores. Being similar to cancellous bone with regard to both interconnected porous structure and mechanical properties, the resulting porous Ti6Al4V is expected to be a promising biomaterial for biomedical applications.
| A novel potential application for 99mTc-HMPAO: endothelial cell labeling for in vitro investigation of cell-biomaterial interactions
Fernandez, P., L. Bordenave, et al. (1999), J Nucl Med 40(10): 1756-63.
Abstract: Good adherence of endothelial cells (ECs) seeded on vascular prostheses and cell retention under flow conditions are important factors to consider in the use of functionalized prostheses in vascular surgery. Because 111In-oxine radiolabeling presents disadvantages, we wondered whether, because of its well-known physical properties, 99mTc-hexamethyl propyleneamine oxime (HMPAO or exametazime) could be used. Methods: The cytotoxicity of unlabeled HMPAO and 99mTc-HMPAO at increasing concentrations and activities was tested on monolayers of the EC line EA-hy-926. The influence of temperature and time on tracer incorporation into cells was also tested. The optimal labeling conditions were applied to evaluate the retention of ECs seeded on polyester grafts under flow conditions by gamma camera detection. Results: The activity of 10 MBq/10(6) cells corresponding to 4.5 microg/10(6) cells of unlabeled HMPAO, applied for 3 h at 37 degrees C (cellular uptake = 18%), was the best compromise between the maintenance of cell viability and metabolic activity and efficient detection by the gamma camera. Spontaneous leakage was observed and analyzed by high-performance liquid chromatography. A cell loss of 13% after 180-min exposure to shear stress was obtained. CONCLUSION: Our data thus indicate the feasibility of using such a radiolabeling technique to investigate EC-biomaterial interactions.
| A novel rabbit model for the evaluation of biomaterial associated urinary tract infection
Fung, L. C., M. W. Mittelman, et al. (2003), Can J Urol 10(5): 2007-12.
Abstract: OBJECTIVES: It was the objective of this study to establish an animal model which simulates the conditions of a biomaterial associated bacterial urinary tract infection. METHODS: The curled portion of polyurethane double pig-tail ureteric stents, pre-coated with P. aeruginosa,were inserted transurethrally into the bladder in eight rabbits. Eight control animals received sterile stent material. Microbiology studies of the stent, bladder tissue, and urine, as well as bladder histopathology were evaluated. RESULTS: P. aeruginosa was recovered from all stent, bladder, and urine specimens in the P. aeruginosa pre-coated stent group, and no P. aeruginosa was present in any of the control specimens (p=0.0002). The controls only developed minimal bladder inflammation, whereas the bladders of the P. aeruginosa pre-coated stent group were significantly more inflamed (p<0.01). CONCLUSIONS: This rabbit model was easy to manipulate, low in maintenance requirements, and had pathophysiologically distinct end points, suitable for the assessment of biomaterial associated urinary tract infections.
| A novel star PEG-derived surface coating for specific cell adhesion
Groll, J., J. Fiedler, et al. (2005), J Biomed Mater Res A 74(4): 607-17.
Abstract: In this study a novel approach for the coating and functionalization of substrates for cell culture and tissue engineering is presented. Glass, silicon, and titanium panes were coated with an ultrathin film (30 +/- 5 nm) of reactive star-shaped poly(ethylene glycol) prepolymers (Star PEG). Homogeneity of the films was checked by optical microscopy and scanning force microscopy. These coatings prevent unspecific protein adsorption as monitored by fluorescence microscopy and ellipsometry. In order to allow specific cell adhesion the films were modified with linear RGD peptides (gRGDsc) in different concentrations. After sterilization, fibroblast, SaOS, and human mesenchymal stem cells (hMSC) were seeded on these substrates. Cell adhesion, spreading, and survival was observed for up to 30 days on linear RGD peptide (gRGDsc)-modified coatings, whereas no cell adhesion could be detected on unmodified Star PEG layers. By variation of the RGD concentration within the film the amount of cells that became adhesive could be controlled. When differentiation conditions are used for cultivation of hMSCs the cells show the expression of osteogenic marker genes after 14 days which is comparable to cultivation on cell culture plastic. Thus, the Star PEG/RGD film did not negatively influence the differentiation process. The high flexibility of the system considering the incorporation of biologically active compounds opens a broad field of future experiments.
| A novel strain sensor based on the campaniform sensillum of insects
Skordos, A., P. H. Chan, et al. (2002), Philos Transact A Math Phys Eng Sci 360(1791): 239-53.
Abstract: The functional design of the campaniform sensillum was modelled as a hole in a plate using two- and three-dimensional finite-element modelling. Different shapes of opening in a fibrous composite plate amplify differently the global strains imposed on the plate, and different configurations of reinforcement also have an effect. In this paper, the main objective is to study the strain and displacement fields associated with circular or elliptical openings in laminated plates in order to investigate their potential for integrated strain sensors. Since we are therefore primarily interested with the detection of displacement, the detailed stress concentration levels associated with these openings are not of primary concern. However, strain energy density levels associated with different hole and fibre configurations have been used to assess the relative likely strength reduction effect of the openings. To compare the relative strain amplification effect of drilled and formed holes of the same size in loaded plates, we have used the relative change in length of diameters (circular) or semi-axes (elliptical) in directions parallel and normal to the load. Various techniques which could sense this deformation were investigated, in particular, the coupling mechanism of a campaniform sensillum of Calliphora vicina. This mechanism was resolved into discrete components: a cap surrounded by a collar, a joint membrane and an annulus-shaped socket septum with a spongy compliant zone. The coupling mechanism is a mechanical linkage which transforms the stimulus into two deformations in different directions: monoaxial transverse compression of the dendritic tip and vertical displacement of the cap. The mechanism is insensitive to change of the material properties of the socket septum, the cuticular cap and the spongy cuticle. The joint membrane may serve as a gap filler. The material properties of the collar have a substantial influence on the coupling mechanism's output. A 30% change of stiffness of the collar causes 45% change in the output of the coupling mechanism. The collar may be able to tune the sensitivity of the sensillum by changing its elastic properties.
| A novel technique for quantitative detection of mRNA expression in human bone derived cells cultured on biomaterials
Zreiqat, H., B. Markovic, et al. (1996), J Biomed Mater Res 33(4): 217-23.
Abstract: A nonisotopic and quantitative in situ hybridization technique was adapted to investigate the effect of biomaterials on the cellular expression of mRNA from human bone derived cells (HBD cells). HBD cells were cultured for 24 or 48 h on tissue culture plastic, alumina, and ion modified alumina. Osteocalcin, osteopontin, alkaline phosphatase, type I collagen alpha 1, and type I collagen alpha 2 mRNAs were quantified. Protein expression for collagen types I, III, and V, and for anti-human macrophages CD68 (DAKO-CD68, KP1) and CD68 (PG-M1), and anti-human myeloid/histiocyte antigen (DAKO-MAC 387) were determined immunohistochemically using monoclonal antibodies. At 24 and 48 h, levels of mRNA for alkaline phosphatase and osteonectin were greater than mRNA levels for osteopontin, osteocalcin, collagen type I alpha 1, and collagen type I alpha 2 for cells grown on the three substrata. However, at 48 h mRNA levels for alkaline phosphatase and osteonectin were significantly higher on the modified ceramic substrata relative to the native alumina. HBD cells appear to express CD68-KP1 when cultured for 24 h. The techniques provide a sensitive and reproducible assay to evaluate gene and protein expression of cells grown on different substrata.
| A novel total knee arthroplasty infection model in rabbits
Craig, M. R., K. A. Poelstra, et al. (2005), J Orthop Res 23(5): 1100-4.
Abstract: Infection of biomaterial implants is an expensive and devastating complication of orthopaedic surgery historically ranging from less than 1% in primary total knee arthroplasty (TKA) to 10% in revision TKA. An in vivo animal model was developed to test the efficacy of innovative therapies for the prevention of biomaterial centered infections caused by methicillin-resistant Staphylococcus aureus bacteria (MRSA). Twenty-two New Zealand White rabbits were used in this study. After proper anesthesia, a stainless-steel screw with a high molecular weight polyethylene (UHMWPE) washer was cemented in a defect created in the intra-articular, non-articulating portion of the lateral femoral condyle of each knee. After closure of the joint capsule, each knee was inoculated with 0, 10(2), 10(3), or 10(4) colony forming units (CFU) of MRSA. Animals were sacrificed after 7 days at which time joint aspirate, tissues and biomaterial samples were examined for evidence of infection. A total of 42 knees were used for analysis. When saline was injected into the knee, 0/10 of the knees demonstrated evidence of biomaterial centered infection (with the contralateral knee receiving 10(4)CFU MRSA). Four of 10 knees developed a biomaterial centered infection when 10(2)CFU MRSA was introduced. Seven out of 10 knees developed a biomaterial centered infection when either 10(3) or 10(4)CFU MRSA was injected. No evidence of septicemia (positive blood cultures) was found in any animal. This rabbit knee model utilizes commonly employed inexpensive orthopaedic implant materials in an in vivo milieu and provides an effective method for the evaluation of treatments for biomaterial centered infections.
| A phase I trial of surgery, Gliadel wafer implantation, and immediate postoperative carboplatin in combination with radiation therapy for primary anaplastic astrocytoma or glioblastoma multiforme
Limentani, S. A., A. Asher, et al. (2005), J Neurooncol 72(3): 241-4.
Abstract: Two types of chemotherapy used in the treatment of patients with malignant glioma are carboplatin and Gliadel wafer [(3.85% 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU)]. To date there have been no published data examining their concurrent use in this disease. The purpose of this study was to evaluate combination chemotherapy with Gliadel wafer and carboplatin in patients with high-grade, malignant glioma. In this prospective phase I study, 16 patients underwent surgery, Gliadel wafer implantation (up to 8 wafers), intravenous carboplatin given postoperatively (day 3 or 4) at a dose escalation range of area under the curve (AUC)=2-6, and external beam radiation. Median age was 55 years (range 27-66 years). Fourteen (88%) patients had glioblastoma multiforme and 2 (12%) had anaplastic astrocytoma. Performance status was as follows: Eastern Cooperative Oncology Group (ECOG)=0 (2 patients), ECOG=1 (13 patients), and ECOG=2 (2 patients). Three patients were treated at each dosing level (AUC=2-6), and 4 patients were treated at an AUC=5. Carboplatin was administered to all patients by postoperative day 4. Radiation was begun on day 14-36. No grade 3 or 4 toxicities were noted in this study. Median progression-free and overall survival was 266 and 679 days, respectively. We conclude that administering systemic carboplatin is safe and well tolerated in the postoperative period immediately following resection and implantation of Gliadel wafer for the treatment of malignant glioma. Further evaluation in a phase II setting, at maximal carboplatin dose to establish potential efficacy, with this combination is warranted.
| A pilot-scale photocatalyst-membrane hybrid reactor: performance and characterization
Ryu, J., W. Choi, et al. (2005), Water Sci Technol 51(6-7): 491-7.
Abstract: We developed and tested a pilot-scale photocatalyst-membrane hybrid reactor for water treatment. The performance of the pilot-scale reactor was evaluated by monitoring the degradation efficiency of several organic pollutants and the membrane suction pressure at different operating conditions. The concentration of humic acids rather increased in the initial period of UV illumination and then decreased gradually, which could be ascribed to the photoinduced desorption of humic acids from the TiO2 surface. The decoloring rate of methylene blue was faster than that of rhodamine B, whereas the order of mineralization rates of the dyes was reversed. 4-chlorophenol of 100 ppb was fully degraded under UV irradiation in 2 hours, which suggests that this hybrid reactor would be more suitable in removing micropollutants in water. The reactor was operated with either continuous or intermittent suction mode. In a continuous suction mode, the formation of TiO2 cake layers on the membrane surface occurred and caused a substantial increase in suction pressure. However, no further fouling (or suction pressure build-up) took place with an intermittent suction mode with the 9-min suction and 3-min pause period. The photocatalyst-membrane hybrid reactor system developed in this study could be an attractive option for controlling micropollutants in water.
| A PLGA membrane controlling cell behaviour for promoting tissue regeneration
Owen, G. R., J. Jackson, et al. (2005), Biomaterials 26(35): 7447-56.
Abstract: Barrier membranes are used in periodontal applications with the aim of supporting bone regeneration by physically blocking migrating epithelial cells. We report a membrane design that has a surface topography that can inhibit epithelial cell migration and proliferation on one side and a topography that guides osteoblast migration to a desired area. A PLGA copolymer (85:15) blended with MePEG, was cast to have surfaces with smooth, grooved or sandblasted-acid-etched topographies. Epithelial cells spread on smooth surfaces after 24 h, and cell numbers increased after 5 days. Cells on the smooth surface exhibited no preferred direction of migration. On the sandblasted-acid-etched topography epithelial cells spread but the cell number did not significantly increase after 5 days. Cell migration was inhibited on this surface. Osteoblasts spread on both grooved and smooth surfaces and cell number increased after 5 days on all surfaces. The cells that adhered in the grooves migrated preferentially in the direction of the grooves. Positive alkaline phosphatase staining was seen on all surfaces within 4 weeks and positive Von Kossa nodule staining within 6 weeks. These results suggest that surface topographies replicated on opposite sides of a biodegradable polymers membrane can inhibit proliferation and migration of the epithelial cells, and promote proliferation and directional migration of osteoblasts. Addition of appropriate surface topographies to membranes used in guided tissue regeneration has the possibility of improving clinical performance in periodontal tissue regeneration procedures.
| A poly(lactic acid)/calcium metaphosphate composite for bone tissue engineering
Jung, Y., S. S. Kim, et al. (2005), Biomaterials 26(32): 6314-22.
Abstract: A new method to prepare PLA/CMP (poly-L-lactide/calcium metaphosphate) composite scaffolds was developed for effective bone tissue engineering. This novel sintering method is composed of pressing the mixture of PLA, CMP, and salt particles at 150 MPa for 3 min followed by heat treatment at 210 degrees C for 30 min. The scaffolds had a homogeneously interconnected porous structure without a skin layer, and they exhibited a narrower pore size distribution and higher mechanical strength in comparison with scaffolds made by a solvent casting method. The scaffolds were seeded by osteoblasts and cultured in vitro or implanted into nude mice subcutaneously for up to 5 weeks. The number of cells attached to and proliferated on the scaffolds at both in vitro and in vivo was in the order of; PLA by novel sintering < PLA/CMP by solvent casting < PLA/CMP by novel sintering. In addition, the alkaline phosphatase activity of and calcium deposition in the scaffolds explanted from mice were enhanced significantly for the scaffolds by novel sintering compared to them by solvent casting. The in vitro results agreed well with the in vivo data. Such a superior characteristic of the novel sintering method should have resulted from the fact that the CMP particles could contact directly with cells/tissues to stimulate the cell proliferation and osteogenic differentiation, while the CMP particles would be coated by polymers and hindered to interact with cells/tissues in the case of a solvent casting method. As the novel sintering method does not use any solvents it offers another advantage to avoid problems associated with solvent residue.
| A potential biomaterial composite for dermal and subcutaneous augmentation
Eppley, B. L., D. J. Summerlin, et al. (1994), Ann Plast Surg 32(5): 463-8.
Abstract: Based on previous experimental connective tissue work in cutaneous wound healing, cell culture, and fat transplantation, the use of positively charged dextran beads for subcutaneous and dermal augmentation was evaluated. When combined with a biocompatible liquid medium, the material easily flowed through small-gauge needles. When injected beneath the facial skin in rats, a profound macrophage response was initially seen at 30 days accompanied by fibroblast proliferation and new collagen formation. By 1 year, a quiescent noninflammatory cellular response with extensive intermaterial collagen deposition was evident. No adverse reactions were seen in the contralateral facial sites, which were injected with only the liquid medium. These preliminary findings suggest good tissue compatibility of this composite biomaterial and provide further evidence of the significant regulatory role of the macrophage in the tissue response to implanted biomaterials.
| A precise radiographic technique for the measurement of dimensional changes in heart valve biomaterials following fixation
Weind, K. L., M. M. Thornton, et al. (2002), J Biomech 35(7): 983-7.
Abstract: Accurate tissue thickness measurements are difficult to acquire by present techniques. Error is introduced by tissue compression during measurements or by tissue processing prior to measurement. In the field of valve replacement, tissue dimensional changes from fixation prior to implantation may predispose implants to premature tissue failure and it becomes important to have an accurate method for comparing cusp dimensions pre- and post-fixation. A new approach is to use high-resolution digital radiography to make thickness maps of entire specimens. For 25 matched porcine aortic valve cusps, we have evaluated this technique's ability to measure and compare thickness, surface area and volume before and after 7 days of aldehyde fixation. Digital radiographs were acquired pre- and post-0.5% glutaraldehyde (n=13) or 10% formaldehyde (n=12) fixation. Mean thickness, surface area, volume and four measurements to evaluate shape differences with fixation were obtained and compared pre- and post-fixation using paired t tests. The results demonstrate that this X-ray imaging technique can provide dimensions of matched fresh and fixed specimens and is sensitive enough to show statistically significant changes due to fixation. These findings also illustrate that aldehyde fixation can cause tissue contraction resulting in a significant overall increase in tissue thickness and a decrease in surface area. This technique could be used to gain further insights into tissue anatomy and mechanics.
| A prospective clinical study of bone augmentation techniques at immediate implants
Chen, S. T., I. B. Darby, et al. (2005), Clin Oral Implants Res 16(2): 176-84.
Abstract: The efficacy of combinations of membranes and autogenous bone grafts at immediate implants were compared in a prospective study. Sixty-two consecutively treated patients each received an immediate implant for a single tooth replacement at a maxillary anterior or premolar site. Dimensions of the peri-implant defect at the implant collar were measured as follows: vertical defect height (VDH), horizontal defect depth (HDD) and horizontal defect width (HDW). Each implant randomly received one of five augmentation treatments and were submerged with connective tissue grafts: Group 1 (n=12)--expanded polytetrafluoroethylene membrane only, Group 2 (n=11)--resorbable polylactide/polyglycolide copolymer membrane only, Group 3 (n=13)--resorbable membrane and autogenous bone graft; Group 4 (n=14)--autogenous bone graft only, and Group 5 (n=12)--no membrane and no bone graft control. At re-entry, all groups showed significant reduction in VDH, HDD and HDW. Comparisons between groups showed no significant differences for VDH (mean 75.4%) and HDD (mean 77%) reduction. Significant differences were observed between groups for HDW reduction (range, 34.1-67.3%), with membrane-treated Groups 1, 2 and 3 showing the greatest reduction. In the presence of dehiscence defects of the labial plate, HDW reduction of 66.6% was achieved with membrane use compared with 37.7% without membranes. Over 50% more labial plate resorption occurred in the presence of a dehiscence defect irrespective of the augmentation treatment used. The results indicate that VDH and HDD reduction at defects adjacent to immediate implants may be achieved without the use of membranes and/or bone grafts.
| A prospective multicenter randomized clinical trial of autogenous bone versus beta-tricalcium phosphate graft alone for bilateral sinus elevation: histologic and histomorphometric evaluation
Szabo, G., L. Huys, et al. (2005), Int J Oral Maxillofac Implants 20(3): 371-81.
Abstract: PURPOSE: Two different graft materials, beta-tricalcium phosphate (Cerasorb) and autogenous bone, were used in the same patient. The objective was to determine whether donor site morbidity could be avoided by using pure-phase beta-tricalcium phosphate (Cerasorb). MATERIALS AND METHODS: Bilateral sinus grafting was performed on 20 selected patients; Cerasorb was used on the experimental side, and autogenous bone was used on the control side. In each patient, one side was randomly designated the experimental side. In 10 of the 20 patients, the maxilla reconstruction included sinus grafting and onlay bone grafting. Implants were placed 6 months after the procedure. In addition to routine panoramic radiographs, in 10 of the 20 patients, 2- and 3-dimensional computerized tomographic examinations were performed pre- and postoperatively and after implantation. Eighty bone biopsy specimens were taken at the time of implant placement. RESULTS: Histologically and histomorphometrically, there was no significant difference between the experimental and control grafts in terms of the quantity and rate of ossification. For each histologic sample, the total surface area, the surface area that consisted of bone, and the surface area that consisted of graft material were measured in mm2, and bone and graft material were analyzed as percentages of the total. The mean percentage bone areas were 36.47% +/- 6.9% and 38.34% +/- 7.4%, respectively; the difference was not significant (P =.25). DISCUSSION AND CONCLUSION: Comparisons with other studies reveal that beta-tricalcium phosphate (Cerasorb) is a satisfactory graft material, even without autogenous bone.
| A prospective multicentre registry of the procedural and long-term clinical and angiographic results of stent implantation using a Dylyn coated coronary stent system
Riezebos, R., E. Ronner, et al. (2004), Int J Cardiovasc Intervent 6(3-4): 137-41.
Abstract: OBJECTIVES: A prospective registry was performed to evaluate the safety and efficacy of a Dylyn coated coronary stent. BACKGROUND: Diamond-like nanocomposite (Dylyn) stent coating is thought to be biocompatible, resulting in decreased thrombogenicity and decreased neointimal hyperplasia. METHODS: In a multicentre, open, prospective, clinical and angiographical registry, the Dylyn-coated stent system was evaluated in patients requiring percutaneous coronary intervention. The primary procedural and angiographical endpoint of the study was the sustained success of stent-implantation using a follow-up catheterisation at six months. The primary clinical endpoint of the study was the composite incidence of death, non-fatal myocardial infarction and revascularisation at six months after stent implantation. RESULTS: 127 Dylyn coated coronary stents were implanted in 121 patients. Procedural success was obtained in 100% of the cases. No episodes of acute stent thrombosis occurred. The number of patients within stent restenosis at six months was 29 (24%). The primary procedural, angiographical endpoint was achieved in 91 (70%) patients. The clinical results at six-month follow-up were favourable with a MACE-rate of 7.4%. CONCLUSIONS: A Dylyn coated coronary stent system is well tolerated and has excellent short-term results. The amount of angiographic restenosis at 6 months, however, is considerable, but comparable to other non-drug-eluting stent systems.
| A quantitative and selective chromatography method for determining coverages of multiple proteins on surfaces
Ombelli, M., R. J. Composto, et al. (2005), J Chromatogr B Analyt Technol Biomed Life Sci 826(1-2): 198-205.
Abstract: Competitive protein adsorption plays a key role in the surface hemocompatibility of biological implants. We describe a quantitative chromatography method to measure the coverage of multiple proteins physisorbed to surfaces. In this method adsorbed proteins are displaced by CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) and then analyzed by high performance liquid chromatography to separate and quantify the individual proteins, in this case bovine serum albumin (BSA) and bovine fibrinogen (Fg). CHAPS displaced over 95% of the adsorbed proteins and was easily removed from solution by dialysis. This method was tested by measuring the coverage of BSA, 66 kDa, and Fg, 340 kDa, simultaneously adsorbed from solutions with concentration of 20 microg/ml, on bare and dextranized silicon. Relative to silicon, the dextranized surfaces were found to strongly inhibit protein adsorption, decreasing BSA and Fg coverages by 76 and 60%, respectively.
| A quantitative microassay for in-vitro toxicity testing of biomaterials
Ulreich, J. B. and M. Chvapil (1981), J Biomed Mater Res 15(6): 913-22.
Abstract: A quantitative tissue culture method is described for toxicity testing of biomaterials. The material to be evaluated, or in the case of insoluble materials--an extract of the material, is incubated on a monolayer of fibroblasts in 24 well culture plates. The activity of the fibroblasts is ascertained by measuring the rate of mitosis (3H-thymidine incorporation), the synthesis of glycosaminoglycans (35SO4= incorporation) or production of total protein (3H-tryptophan incorporation). By proper choice of label, the effect of the biomaterial on cellular proliferation or production of macromolecules or both may be assessed. Materials with a cytotoxic effect cause inhibition of incorporation of radioactive label in the above assays. The cell monolayers can also be inspected microscopically for evidence of cytotoxicity. The method is quantitative, simple, reproducible, rapid, and suitable for screening of a large number of samples.
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