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Record 2601 to 2620

Invasiveness of fibroblast-like synoviocytes is an individual patient characteristic associated with the rate of joint destruction in patients with rheumatoid arthritis
Tolboom, T. C., A. H. van der Helm-Van Mil, et al. (2005), Arthritis Rheum 52(7): 1999-2002.
Abstract: OBJECTIVE: Rheumatoid arthritis (RA) is characterized by inflammation and destruction of synovial joints. Fibroblast-like synoviocytes (FLS) harvested from synovial tissue of patients with RA can invade normal human cartilage in severe combined immunodeficient (SCID) mice and Matrigel basement membrane matrix in vitro. This study was undertaken to investigate the association of these in vitro characteristics with disease characteristics in patients with RA. METHODS: Synovial tissue samples from 72 RA and 49 osteoarthritis (OA) patients were obtained. Samples of different joints were collected from 7 patients with RA. The FLS invasiveness in Matrigel was studied, and the intraindividual and interindividual differences were compared. From the patients with FLS who exhibited the most extreme differences in in vitro ingrowth (most and least invasive FLS), radiographs of the hands and feet were collected and scored according to the Sharp/van der Heijde method to determine the relationship between in vitro invasion data and estimated yearly joint damage progression. RESULTS: FLS from patients with RA were more invasive than FLS from patients with OA (P < 0.001). The mean intraindividual variation in FLS invasion was much less than the mean interindividual variation (mean +/- SD 1,067 +/- 926 and 3,845 +/- 2,367 for intraindividual and interindividual variation, respectively; P = 0.035), which shows that the level of FLS invasion is a patient characteristic. The mean +/- SEM Sharp score on radiographs of the hands or feet divided by the disease duration was 4.4 +/- 1.1 units per year of disease duration in patients with the least invasive FLS (n = 9), which was much lower compared with the 21.8 +/- 3.1 units per year of disease duration in patients with the most invasive FLS (n = 9) (P < 0.001). CONCLUSION: The ex vivo invasive behavior of FLS from RA patients is associated with the rate of joint destruction and is a patient characteristic, given the much smaller intraindividual than interindividual FLS variation.

Investigation into potential mechanisms promoting biocompatibility of polymeric biomaterials containing the phosphorylcholine moiety A physicochemical and biological study
Parker, A. P., P. A. Reynolds, et al. (2005), Colloids Surf B Biointerfaces
Abstract: Phosphorylcholine (PC) moieties were chemically attached to surfaces of polymer microparticles by addition of 2-methylacryloyloxyethyl phosphorylcholine monomer to the seeded, semi-continuous polymerisations of methyl methacrylate (MMA) and butyl acrylate (BA). The surface of the bio-functionalised polymer microparticles was principally characterised using X-ray photoelectron spectroscopy (XPS), dynamic nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), photon correlation spectroscopy (PCS), acoustophoresis and enzyme-linked immunosorbent assays (ELISA). It was found that the persulphate initiating species are concealed behind the phosphorylcholine containing monomer sequence located on the surface of the microparticles. The combination of analytical techniques showed that the surfaces of the polymer microparticles are extremely mobile above the glass transition temperature of the co-polymer and able to rearrange depending on the environment in which they are placed. This allows the phosphorylcholine moiety to be preferentially expressed at the surface in aqueous media, but not so in the dry state or conditions of ultra-high vacuum. In terms of the nature of the biocompatibility of phosphorylcholine containing polymers, no evidence was found for the irreversible structuring of water molecules around the phosphorylcholine moiety in the wet state. The results of this work suggest that a more likely contributory reason for the protein-resistant nature of phosphorylcholine containing polymers is the mobility of the phosphorylcholine moiety. Increases in biocompatibility correspond with increases in the hydrophilicity of a polymer surface when phosphorylcholine is preferentially expressed. A large free water fraction may be present in the phosphorylcholine containing monomer sequence, as part of a hydrogel structure located at the surface of the polymer microparticles. This, coupled with concomitant modification of the local electrical double-layer very close to the surface may also play a critical role in reducing protein-surface interactions.

Investigation of a new microcapsule membrane combining alginate, chitosan, polyethylene glycol and poly-L-lysine for cell transplantation applications
Haque, T., H. Chen, et al. (2005), Int J Artif Organs 28(6): 631-7.
Abstract: Microencapsulation of living cells may serve as an alternative therapy for patients requiring organ transplants. One of the limiting factors in the progress of such therapy is attaining a biocompatible and mechanically stable polymer. The current study investigates the potential of a novel membrane combining alginate, chitosan, polyethylene glycol (PEG) and poly-L-lysine (PLL) with the objective of proposing a membrane suitable for cell entrapment that may overcome some of the shortcomings of the widely studied alginate-poly-L-lysine-alginate (APA) capsules. The novel microcapsule was formulated using a 1.5% alginate solution coated with 0.05% chitosan, 0.1% PEG and 0.05% poly-L-lysine with a final layer of 0.1% alginate. Microcapsules having a diameter of 450 +/- 30 microm were prepared. Upon citrate treatment, the membrane remained intact and retained its spherical structure. The membrane was able to support liver cell proliferation and the encapsulated cells were capable of secreting proteins. The study demonstrated that the new membrane can be used for cell entrapment. However, further investigations are needed to assess its potential for long term transplantation and usage in the development of bioartificial organs.

Investigation of application of PHA coating to enhance biocompatibility of vascular stents
Protopopov, A. V., T. A. Kochkina, et al. (2005), Dokl Biol Sci 401: 85-7.

Investigation of blood-biomaterial interaction by means of a new quantitative dynamic measuring principle
Groth, T., C. Vassilieff, et al. (1990), Biomater Artif Cells Artif Organs 18(4): 517-22.
Abstract: In this study a new dynamic measuring chamber for flat biomaterials allowing the estimation of cell adhesion on test surfaces by measuring the cell lost from surface contacting test blood under defined rheological conditions is introduced. This was achieved by constructing a test chamber permitting the contact of small amount of blood with a large geometrical test surface. The construction consists of a spiral-shaped flow channel of 0.3 cm width, 0.02 cm height and 78 cm length. The applicability of the new method was demonstrated by evaluation of platelet adhesion on siliconized glass, fibrinogen coated glass, cuprophane and polyacrylnitrile.

Investigation of novel alginate-magnesium aluminum silicate microcomposite films for modified-release tablets
Pongjanyakul, T., A. Priprem, et al. (2005), J Control Release 107(2): 343-56.
Abstract: Physicochemical properties of sodium alginate-magnesium aluminum silicate (SA-MAS) composite films were investigated and a potential as a film former of SA-MAS dispersion for modifying drug release from tablets was evaluated as well. Interaction between SA and MAS in the composite films was revealed using FTIR spectroscopy. Thermal behavior of the composite films was changed due to the complexation of SA and MAS. Powder X-ray diffractometry data suggested that a higher crystallinity of the composite film and a phase-separated microcomposite were formed. The composite films in the ratios of 1:0.5 and 1:1 showed the increases of tensile strength and percentage of elongation when compared with SA films. Water vapor permeability of the composite films tended to increase with increasing ratio of MAS. The decreases in water uptake and drug permeability in 0.1 M HCl were found in the composite films. A positive charge drug, propranolol HCl, provided a higher affinity on the composite films than a weakly acidic nonelectrolyte, acetaminophen, resulting in a longer lag time and a higher partition coefficient depending on the content of MAS in the composite films. This was due to the complex formation of propranolol HCl and MAS. Using SEM, the tablets coated with SA-MAS dispersion had a smooth surface, while those with SA dispersion showed a pinholing on the surface, resulting in a faster drug release. The drug release profiles of the tablets could be modified by coating with the composite film at different coating levels. This finding suggests that MAS could improve physicochemical properties of the SA films, leading to a novel coating material of the SA-MAS dispersion for modifying drug release from tablets.

Investigation of primary cell-biomaterial interactions using silver nitrate staining of nucleolar organising regions
Flynn, J. M., R. M. Shelton, et al. (2002), Biomaterials 23(1): 19-26.
Abstract: The quantification of silver nitrate staining of nucleolar organising regions (AgNORs) within the nucleus of the cell has been shown to give a relative measure of the metabolic activity of the cell. In the present study, silver nitrate staining was utilised to identify metabolic variations in cells cultured on different surfaces and compared with proliferative activity assessed using bromodeoxyuridine (BrdU) uptake. Primary osteoblast and periosteal cells, isolated from the calvaria of neonate rats, were cultured on tissue culture-grade (TCPS) and bacteriological-grade (BACPS) polystyrene petri dishes for 3, 5, 7 and 9 days (silver nitrate) or 14 days (BrdU). The phenotype of the cells was examined using RT-PCR of the mRNA for osteocalcin, collagen 1a, alkaline phosphatase and osteopontin. The number and area of AgNORs and the proportion of BrdU positive cells were statistically different in cells cultured on TCPS compared with BACPS at each culture period tested. The results suggest that the metabolic activity and proliferation of cells were affected by the substrate which they colonise.

Investigation of surface changes in different types of ventilation tubes using scanning electron microscopy and correlation of findings with clinical follow-up
Tatar, E. C., F. O. Unal, et al. (2005), Int J Pediatr Otorhinolaryngol
Abstract: OBJECTIVES: Like all biomaterials, ventilation tubes are subject to formation of bacterial biofilm on their surfaces. There might also be surface changes. This increases the risk of complications associated with ventilation tubes. In this study, we examined two groups of ventilation tubes using scanning electron microscopy (SEM) to investigate biofilm growth and surface deformations. METHODS: There were two different types of ventilation tubes used, the first group consisted of 30 silicone tubes and the second group consisted of 16 ionized, processed silicone tubes. The tube samples included those that were either removed or those that were extruded into the ear canal. We investigated the association between scanning electron microscopy findings and the complications that developed during the treatment. RESULTS: As a result of this study, it is found that the ionized, processed silicone tubes are superior to other silicon ventilation tubes in regard to biofilm growth (z=-3.925, p=0.000, <0.0001) and surface deformations (chi(2)=9.120, p=0.003, <0.01). Furthermore, we observed that as the duration of the ventilation tube application increases, bacterial biofilm growth (chi(2)=10.718, p=0.005, <0.01) and surface deformations (z=-2.940, p=0.003, <0.01) increase. We also observed that biofilm growth and occurrence frequency were related to "otorrhea" (chi(2)=10.258, p=0.036, <0.05) and "plugging" (chi(2)=7.952, p=0.019, <0.05) complications. CONCLUSION: In this study, we show that ionized, processed silicone ventilation tubes are more robust to bacterial biofilm growth compared to other silicone ventilation tubes used in this study and that the "otorrhea" and "plugging" complications are reduced with the decrease of bacterial biofilm growth.

Investigations using clinically relevant particles. Reference: Im et al., The effect of COX-2 inhibitors on periprosthetic osteolysis, Biomaterials 25, 269-275 (2004)
Shanbhag, A. (2005), Biomaterials 26(20): 4349-50.

In-vitro hemocompatibility evaluation of a thermoplastic polyurethane membrane with surface-immobilized water-soluble chitosan and heparin
Lin, W. C., C. H. Tseng, et al. (2005), Macromol Biosci 5(10): 1013-21.
Abstract: The surface of a thermoplastic polyurethane (TPU) membrane was treated with low temperature plasma (LTP) and was then grafted with poly(acrylic acid) (PAA), followed by the grafting of water-soluble chitosan (WSC) and heparin (HEP). The surface was characterized with static contact-angle and X-ray photoelectron spectroscopy (XPS). The results showed that the surface densities of peroxides and PAA reached a maximum when treated with LTP for 90 s. A higher pH of the reacting solution led to higher graft densities of WSC and HEP. After WSC and HEP grafting, the hydrophilicity of the TPU membrane was increased. The adsorption of proteins on HEP-grafted TPU membranes was effectively curtailed. In addition, HEP grafting also reduced platelet adhesion, elevated thrombin inactivation, and prolonged the blood coagulation time. According to the L929 fibroblast cell growth inhibition index, the HEP-grafted TPU membranes exhibited non-cytotoxicity. Overall results demonstrated that the HEP immobilization could not only improve the hydrophilicity but also the hemocompatibility of the TPU membrane, while maintaining the ascendant biocompatibility.

Invitro study of adherent mandibular osteoblast-like cells on carrier materials
Turhani, D., M. Weissenbock, et al. (2005), Int J Oral Maxillofac Surg 34(5): 543-50.
Abstract: Augmentation of the craniofacial region is necessary for many aesthetic and reconstructive procedures. Tissue engineering offers a new option to supplement existing treatment regimens. In this procedure, materials composed of hydroxyapatite (HA), of synthetic or natural origin, are used as scaffolds. The aim of this study was to evaluate the effects of three HA materials on cultured human osteoblasts in vitro. Explant cultures of cells from human alveolar bone were established. Human osteoblasts were cultured on the surface of HA calcified from red algae (C GRAFT/Algipore), deproteinized bovine HA (Bio-Oss) and bovine HA carrying the cell binding peptide P-15 (Pep Gen P-15). Cultured cells were evaluated with respect to cell attachment, proliferation and differentiation. Cells were cultured for 6 and 21 days under osteogenic differentiation conditions, and tissue-culture polystyrene dishes were used as control. The ability of cells to proliferate and form extracellular matrix on these scaffolds was assessed by a DNA quantification assay, protein synthesis analysis and by scanning electron microscopical examination. Osteogenic differentiation was screened by the expression of alkaline phosphatase. The osteoblastic phenotype of the cells was monitored using mRNA levels of the bone-related proteins including osteocalcin, osteopontin and collagen Type I. We found that cells cultured on C GRAFT/Algipore) and Pep Gen P-15 showed a continuous increase in DNA content and protein synthesis. Cells cultured on Bio-Oss showed a decrease in DNA content from Day 6 (P < 0.05) to Day 21 (P < 0.0001) and protein synthesis on Day 21 (P < 0.005). Alkaline phosphatase activity increased in cells grown on C GRAFT/Algipore and Pep Gen P-15 in contrast to cells grown on Bio-Oss, in which the lowest levels of activity could be observed on Day 21 (P < 0.05). Reverse transcriptase polymerase chain reaction analysis confirmed the osteoblastic phenotype of the cells grown on all three materials throughout the whole culture period. The results of our in vitro study show that the differences in metabolic activity of cells grown on HA materials are directly related to the substrate on which they are grown. They confirm the excellent properties of HA carrying the cell binding peptide P-15 and HA calcified from red algae as used in maxillofacial surgery procedures.

Involvement of tissue transglutaminase in the stabilisation of biomaterial/tissue interfaces important in medical devices
Heath, D. J., P. Christian, et al. (2002), Biomaterials 23(6): 1519-26.
Abstract: Tissue transglutaminase (tTG) has recently been established as a novel cell surface adhesion protein that binds with high affinity to fibronectin in the pericellular matrix. In this study, we have made use of this property to enhance the biocompatibility of poly(epsilon-caprolactone) (PCL), a biomaterial currently used in bone repair. Poly(epsilon-caprolactone) discs were first coated with fibronectin and then tTG. The surface localisation of the two proteins was confirmed using ELISA and the tTG shown to be active on the surface by incorporation of biotin cadaverine into the fibronectin coating. When human osteoblasts (HOBs) were seeded onto the coated polymer surfaces in serum free medium, the surface coated with fibronectin and then tTG showed an increase in the spreading of the cells as compared to the surface coated with fibronectin alone, when analysed using environmental scanning electron microscopy. The presence of tTG had no effect on HOB cell differentiation when analysed by determining alkaline phosphatase activity. The use of tTG as a novel adhesion protein in this way may therefore have considerable potential in forming a stable tissue/biomaterial interface for application in medical devices.

Ion exchanges in apatites for biomedical application
Cazalbou, S., D. Eichert, et al. (2005), J Mater Sci Mater Med 16(5): 405-9.
Abstract: The modification of the composition of apatite materials can be made by several processes corresponding to ion exchange reactions which can conveniently be adapted to current coatings and ceramics and are an alternative to setting up of new synthesis methods. In addition to high temperature thermal treatments, which can partly or almost totally replace the monovalent OH- anion of stoichiometric hydroxyapatite by any halogen ion or carbonate, aqueous processes corresponding to dissolution-reprecipitation reactions have also been proposed and used. However, the most interesting possibilities are provided by aqueous ion exchange reactions involving nanocrystalline apatites. These apatites are characterised by the existence on the crystal surface of a hydrated layer of loosely bound mineral ions which can be easily exchanged in solution. This layer offers a possibility to trap mineral ions and possibly active molecules which can modify the apatite properties. Such processes are involved in mineralised tissues and could be used in biomaterials for the release of active mineral species.

Ionic liquid-reconstituted cellulose composites as solid support matrices for biocatalyst immobilization
Turner, M. B., S. K. Spear, et al. (2005), Biomacromolecules 6(5): 2497-502.
Abstract: Preparation of cellulose-polyamine composite films and beads, which provide high loading of primary amines on the surface allowing direct one-step bioconjugation of active species, is reported using an ionic liquid (IL) dissolution and regeneration process. Films and bead architectures were prepared and used as immobilization supports for laccase as a model system demonstrating the applicability of this approach. Performance of these materials, compared to commercially available products, has been assessed using millimeter-sized beads of the composites and the lipase-catalyzed transesterification of ethyl butyrate.

Ionically crosslinked alginate/carboxymethyl chitin beads for oral delivery of protein drugs
Shi, X. W., Y. M. Du, et al. (2005), Macromol Biosci 5(9): 881-9.
Abstract: Complex beads composed of alginate and carboxymethyl chitin (CMCT) were prepared by dropping aqueous alginate-CMCT into an iron(III) solution. The structure and morphology of the beads were characterized by IR spectroscopy and scanning electron microscopy (SEM). IR confirmed electrostatic interactions between iron(III) and the carboxyl groups of alginate as well as CMCT, and the binding model was suggested as a three-dimensional structure. SEM revealed that CMCT had a porous morphology while alginate and their complex beads had a core-layer structure. The swelling behavior, encapsulation efficiency, and release behavior of bovine serum albumin (BSA) from the beads at different pHs were investigated. The BSA encapsulation efficiency was fairly high (>90%). It was found that CMCT disintegrated at pH 1.2 and alginate eroded at pH 7.4 while the complex beads could effectively retain BSA in acid (>85%) and reduce the BSA release at pH 7.4. The results suggested that the iron(III)-alginate-CMCT bead could be a suitable polymeric carrier for site-specific protein drug delivery in the intestine.

Ionotropic alginate beads for controlled intestinal protein delivery: effect of chitosan and barium counter-ions on entrapment and release
Bhopatkar, D., A. K. Anal, et al. (2005), J Microencapsul 22(1): 91-100.
Abstract: Alginate beads containing the model protein haemoglobin (Hb) were prepared by coagulation with various counter-ions to improve the controlled release of the protein. The effect of Ba(2+) and Ca(2+) ions and of the polycationic polysaccharide chitosan was investigated. Coagulation with Ba(2+), Ca(2+) and/or chitosan showed differences in the swelling index of the beads, in the encapsulation efficiency of Hb entrapment and in the release of the entrapped protein. Chitosan in the coagulation fluid markedly enhanced the encapsulation efficiency of the Hb. Release studies were conducted in simulated gastric fluid (SGF pH approximately or equal to 1.2) and subsequently in simulated intestinal fluid (SIF) at 37 degrees C. Beads were stable in the gastric fluid but released their protein upon transfer to intestinal fluid. The release coincides with the burst and disintegration of beads. Rate of protein release from the beads was affected by the Ba(2+) and chitosan concentration in coagulation fluid.

Iridium nanocrystal synthesis and surface coating-dependent catalytic activity
Stowell, C. A. and B. A. Korgel (2005), Nano Lett 5(7): 1203-7.
Abstract: Iridium (Ir) nanocrystals were synthesized by reducing (methylcyclopentadienyl)(1,5-cyclooctadiene)lr with hexadecanediol in the presence of four different capping ligand combinations: oleic acid and oleylamine, trioctylphosphine (TOP), tetraoctylammonium bromide (TOAB), and tetraoctylphosphonium bromide (TOPB). The oleic acid/oleylamine-capped nanocrystals were of the highest quality, with the narrowest size and shape distribution. The Ir nanocrystals were tested for their ability to catalyze the hydrogenation of 1-decene as a model reaction. The oleic acid/oleylamine and TOP-capped nanocrystals were both catalytically dead. TOAB and TOPB-coated nanocrystals both catalyzed 1-decene hydrogenation, with the TOPB-coated nanocrystals exhibiting the highest turnover frequencies. Recycling through several catalytic reactions increased the catalytic activity, presumably as a result of ligand desorption and increased exposure of the metal surface, with ligand desorption eventually leading to precipitation and significantly decreased activity.

Irritation and cytotoxic potential of denture adhesives
Al, R. H., J. E. Dahl, et al. (2005), Gerodontology 22(3): 177-83.
Abstract: OBJECTIVE: The present study aimed to examine the in vitro biocompatibility of denture adhesives. BACKGROUND: Denture adhesives absorb water to become viscous and sticky, and by this process, other constituents like colouring, flavouring, wetting and preserving agents may be released. Some of these constituents may induce adverse reactions among users of denture adhesives. MATERIALS AND METHODS: Five commercially available denture adhesives; three different creams, a powder, and a cushion were included in the study. The irritation and cytotoxic potential was evaluated using the Hen's Egg Test Chorioallantoic Membrane (HET-CAM) method and three cell culture methods; filter diffusion, dimethylthiazol diphenyltetrazolium bromide (MTT) assay and agar diffusion. RESULTS: None of the tested denture adhesives showed a noteworthy acute irritation as evaluated by the HET-CAM method. None of the tested denture adhesives induced cytotoxicity in the filter diffusion test. One of the denture adhesives induced a severe cytotoxic reaction in both the MTT and agar diffusion assays. These tests employ longer exposure times than in both the filter diffusion and the HET-CAM test. CONCLUSION: Denture adhesives are commonly used throughout the day, and our results raise the concern that denture adhesives may contribute to mucosal inflammation in denture wearers.

Is aseptic loosening truly aseptic?
Nelson, C. L., A. C. McLaren, et al. (2005), Clin Orthop Relat Res(437): 25-30.
Abstract: Surgeons who treat osteomyelitis or infected implants think that microorganisms can live on and around implanted biomaterials and necrotic bone without clinical manifestations of infection. Gristina and Costerton, in their seminal work, suggested that such bacteria persist within biofilms and that they are often overlooked when diagnosis is based on standard microbiologic culture techniques. Subsequent studies using specialized techniques including sonication to remove adherent bacteria and direct detection using various forms of microscopy have confirmed that bacteria are present in many culture-negative cases. This led to the suggestion that at least some cases of failed orthopaedic implants that were considered aseptic loosening based on the absence of clinical signs of infection and the failure to isolate bacteria may actually have an infectious etiology. In addition to biofilms, potentially important concepts that also may contribute to false-negative culture results include the failure to recognize small colony variants induced during growth in vivo and the presence of bacteria inside host cells including osteoblasts. Importantly, bacteria persisting as small colony variants within biofilms and/or inside osteoblasts also may be an explanation for the recurrent nature of musculoskeletal infection.

Is hydroxyapatite ceramic an adequate biomaterial in ossicular chain reconstruction?
Hormann, K. and K. Donath (1987), Am J Otol 8(5): 402-5.
Abstract: The suitability of high-density hydroxyapatite ceramic without macropores for ossicular chain reconstruction was examined in animal experiments. The material was implanted both mobilely and immobilely, in compact cylinders and as granules at different locations. Biocompatibility was studied by the sawing and grinding technique without decalcification. If high-density hydroxyapatite was not in direct and stable contact with living bone, resorption and osteoneogenesis could not be observed. In cases of mobile contact with living bone there was a jointlike connection. Osteoneogenesis was seen only if the hydroxyapatite was in primary stable contact with living bone. We concluded that high-density hydroxyapatite ceramic, positioned as an ossicular replacement prosthesis, is an adequate biomaterial in ossicular chain reconstruction.

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