摘要:

The tissue biocompatibility of a series of novel rubbery polyisobutylene (PIB)/polydimethylsiloxane (PDMS) bicomponent networks was investigated by in vivo implantation into rats. Bicomponent networks of varying composition (PIB wt%/PDMS wt% = 70/30, 50/50, 35/65) as well as a standard polyethylene control were implanted intraperitoneally. After eight weeks the implants and surrounding tissue were removed for histological evaluation. In all scoring categories (i.e. collagen thickness, fibrous tissue orientation, collagen deposition in muscle tissue, lymphocyte infiltration, angiogenesis) the PIB/PDMS bicomponent network implants elicited either less or similar tissue and cellular response than polyethylene. To determine which implant elicited the least tissue and cellular response overall, a weighted score including collagen thickness, lymphocyte infiltration, and angiogenesis was calculated for each implant. According to these preliminary investigations, PIB/PDMS bicomponent networks are suitable for implant applications.

ISSN:0920-5063    

DOI:10.1163/156856299X00333

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

To improve the surface blood compatibility on a cellulose hemodialysis membrane, 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers with a phospholipid polar group were immobilized on the surface through covalent bonding. The MPC polymers had a carboxylic group, which can react with hydroxyl groups on the cellulose membrane, and were synthesized by conventional radical polymerization. The reaction between the MPC polymers and the cellulose membrane was carried out in a heterogeneous system using a condensation reagent. Surface analysis of the modified membrane by X-ray photoelectron spectroscopy revealed the immobilization of the MPC polymer on the surface. The mechanical strength and permeability for a solute of the membrane did not change even after the modification. The modified cellulose membrane was blood-compatible, as determined by the prevention of adhesion, deformation, and aggregation of platelets after contact with platelet-rich plasma. Based on these results, it is concluded that the MPC polymers may be a useful material for improving the blood compatibility of cellulose hemodialysis membranes.

ISSN:0920-5063    

DOI:10.1163/156856299X00342

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Surface topography appears to be an important but often neglected factor in implant performance. In this study, fibroblasts were cultured on a range of porous polycarbonate (PC) membranes with well defined surface topography (track-etched micropores, 0.2-8.0 μm in diameter) and wcttability gradients. The wettability gradient on the PC membrane surfaces was produced by treating the surfaces with corona from a knife-type electrode whose power increased gradually along the sample length. The PC membrane surfaces were characterized by scanning electron microscopy (SEM) and the water contact angle measurement. Fibroblasts were cultured on the corona-treated PC membrane surfaces with different micropore sizes for 1 and 2 days. The cells attached on the membrane surfaces were examined by SEM and the cell density on the surfaces was estimated by counting the number of attached cells along the wettability gradient. It was observed that the cells were adhered and grew more on the hydrophilic positions of the membrane surfaces than the more hydrophobic ones, regardless of micropore size. It was also observed that cell adhesion and growth decreased gradually with increasing micropore size of the membrane surfaces. It seems that the cell adhesion and growth were progressively inhibited as the membrane surfaces had micropores with increasing size, probably due to surface discontinuities produced by tract-etched pores. On the membrane surfaces with smaller micropore sizes, the cells seemed to override these surface discontinuities.

ISSN:0920-5063    

DOI:10.1163/156856299X00351

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The effect of endothelial cell adhesion on polyurethanes coated with Langmuir-Blodgett antibody films has been examined. The films were cross-linked with glutaraldehyde with the aim of providing a densely packed and covalently linked two-dimensional antibody network on the polyurethane surfaces. Our results demonstrate that although neither of the two polyurethanes examined were entirely suited to cellular adhesion, Langmuir-Blodgett antibody films, cross-linked with small concentrations of glutaraldehyde, are more suitable for endothelial cell adhesion than surfaces free of antibody.

ISSN:0920-5063    

DOI:10.1163/156856299X00360

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Poly(2-hydroxyethylmethacrylate) (PHEMA) microbeads prepared by suspension polymerization were treated with diamine-plasmas (i.e. ethylene-diamine (EDA) and hexamethylene diamine (HMDA)) in a glow-discharge reactor in which the exposure time and glow-discharge power were changed between 5 and 30 min and 5 and 20 W, respectively. The amount of nitrogen deposition increased both with increase in exposure time and glow-discharge power. The maximum amounts of nitrogen deposition on the microbeads were 22.3 and 23.4 μmol g-1with the EDA- and HMDAplasmas. Then, Cu(II) ions were incorporated onto the PHEMA microbeads by chelating with the nitrogen-carrying functional groups. Different amounts of Cu(II) ions (2.4-6.8 mg g-1) were incorporated on the PHEMA microbeads by changing the initial concentration of Cu(II) ions. Bovine serum albumin (BSA) adsorption onto the unmodified PHEMA, diamine-plasma treated PHEMA, and diamine-plasma treated Cu(II)-incorporated PHEMA microbeads was investigated. The nonspecific adsorption of BSA on the unmodified microbeads was very low (0.22 mg BSA g-1). Deposition of nitrogen increased the BSA adsorption (9.3 mg g-1for EDA-plasma and 12.7 mg g-1for HMDA-plasma). Cu(II)-incorporation significantly increased the BSA adsorption (154 mg g-1for EDA-plasma and 178 mg g-1for HMDA-plasma). Further increases in the albumin adsorption capacities of the polymer microbeads (185 mg g-1for EDA-plasma and 208 mg g-1for HMDA-plasma) were observed when human plasma was used. More than 92% of the adsorbed albumin molecules was desorbed in 1 h in the desorption medium containing 0.5 M NaSCN at pH 8.0. Repeated adsorption-desorption cycles showed the feasibility of these plasma-modified polymer microbeads.

ISSN:0920-5063    

DOI:10.1163/156856299X00379

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Expanded polytetrafluoroethylene (ePTFE) implants are being increasingly used as vascular prostheses and other devices. However the tissue response associated with this and other polymer implants continues to limit any long-term function. One of the major approaches currently being investigated to improve biocompatibility involves surface modification of the base polymer. In this report, we attempted to alter the healing characteristics of ePTFE by denucleation, a process which removes air trapped within the interstices of the material. Additionally, adsorption of extracellular proteins on the denucleated polymer was also tested. After 5 weeks implanted in subcutaneous and epididymal fat sites of rats, the material was explantcd and the healing around the implant evaluated histologically. We found that in skin implants, denucleation alone resulted in a substantial reduction in the fibrous capsule which has been previously reported for untreated ePTFE, and an increase in blood vessel development around and within the polymer. Absorption of extracellular matrix proteins prior to implantation resulted in a reduced vascularity of the implants compared with denucleation-only implants. Implants in fat tissue, regardless of treatment, showed very little tissue reaction, either in the number of inflammatory cells, development of a fibrous capsule or neovascularization. These results suggest that the presence of air nuclei within porous material may contribute to the inappropriate healing response associated with these polymers. In addition, they confirm earlier reports that healing around implanted polymers is tissue-specific.

ISSN:0920-5063    

DOI:10.1163/156856299X00388

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In our previous study, we reported a novel method of apatite formation on/in a three-dimensional hydrogel matrix. Using this method, bone-like apatite could be formed on/in the hydrogel matrix under normal conditions in vitro. A poly(vinyl alcohol) (PVA) gel was used as a model matrix. The method consists of two steps: first, water is transformed in a PVA gel with a CaCl2/Tris-HCl aqueous solution (pH 7.4) and second, the gel is soaked in a Na2HPO4aqueous solution. In the present study, we report a detailed study of the effects of the swelling ratios of PVA gels on apatite formation. Cross-sectional observations and gravimetric measurements of PVA gels with various swelling ratios were done. The amount of apatite formed on/in PVA gels increased almost linearly with an increase in the reaction cycles. The rates of apatite formation on/in PVA gels largely depended on the swelling ratios, which were approximately 0.48, 0.61, 1.28, and 1.55 mg per cycle for swelling ratios of 4.1, 10.4, 16.8, and 30.1, respectively. The apatite content in PVA-apatite composites that was obtained by this method also increased with an increase of the reaction cycles. After six reaction cycles, a PVA gel with a high swelling ratio contains approximately 70 wt% of formed apatite in the composite. On the other hand, a gel with a low swelling ratio contains about 15 wt% of formed apatite in the composite. Cross-sectional views of the PVA gels after each cycle showed that apatite crystals were formed, not only on the surface of the gel but also within it after fifteen reaction cycles. The hydrogel-apatite composites that were obtained using an alternative soaking process will be useful as not only bone substitute materials but also as soft tissue adhesive materials.

ISSN:0920-5063    

DOI:10.1163/156856299X00397

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new DNA-immobilized immunoadsorbent was prepared to remove the pathogenic anti-DNA antibody from the serum of systemic lupus erythematosus (SLE) patients. A non-woven poly(ethylene terephthalate) (PET) fabric made of 3.5-μm diameter fibers was used as the support of the immunoadsorbent. A cationic monomer, N,N-dimethylaminoethyl methacrylate (DAM), was graft polymerized onto the PET fiber surface by UV irradiation or with a chemical initiator. Polyion complexation between the cationic groups of the graft chains and DNA molecules was employed to immobilize DNA onto the fiber surface. No DNA leaching was observed when the DNA-immobilized fabrics were placed in 0.9 and 2.0 wt% NaCl solution at 37 °C overnight. In vitro evaluation of this DNA-immobilized immunoadsorbent demonstrated that this adsorbent could selectively adsorb anti-DNA antibody from the serum of SLE patients.

ISSN:0920-5063    

DOI:10.1163/156856299X00405

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Properties of collagen irradiated with ultraviolet (UV) light were examined using the techniques of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, spectroscopic measurements. and cell adhesion assay. Both photopolymerization and photodegradation of the collagen appeared to occur with UV irradiation because the aggregation of collagen and disintegration of the triple-helical structure were observed. The formation of the cross-links between the tyrosine residues in collagen by photoreaction was presumed. The adhesion of macrophages (Møs) on a polystyrene plate was suppressed by coating the plate surface with collagen. Anti-adhesive activity of collagen on Mø cells decreased with UV irradiation. However, appreciable anti-adhesive activity remained in the modified collagen even when collagen was irradiated with UV light for 24 h.

ISSN:0920-5063    

DOI:10.1163/156856299X00414

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

To synthesize high molecular weight poly(propylene fumarate) (PPF). fumaryl chloride and propylene glycol were reacted in the presence of potassium carbonate, which serves as a proton scavenger. Transesterification of the resulting low molecular weight oligomer led to a polymer with greater molecular weight than those from previous reaction methods without requiring the use of a catalyst. According to two-dimensional NMR, the backbone structure of this polymer was as expected and contained no byproducts formed by acid catalyzed addition across the fumarate double bond. Kinetic studies of the transesterification showed that the molecular weight reached a final Mnof 4900 (±700) and Mwof 9100 (±1300) after 16 h. while the polydispersily index remained below 1.8 throughout the reaction. Thus the PPF synthesized by the new method is of higher molecular weight and greater purity than our previously prepared material.

ISSN:0920-5063    

DOI:10.1163/156856299X00423

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor