摘要:

Biospecific functional polymers, i.e. synthetic or artificial polymers substituted with specific chemical functional groups carried by the macromolecular chain are designed to interact with living systems. These polymers are either insoluble or soluble, derived from polystyrene and dextran. Polymers substituted with aryl sulfonate and carboxyl groups specifically interact with antithrombin III and serine-proteases involved in the coagulation of blood. As a consequence, these polymers possess heparin-like activity and are therefore of low thrombogenicity when exposed to flowing blood. Other functional polymers have been prepared in order to interact with various components of the immune system. Soluble and insoluble functional polymers in contact with cells can affect both cell proliferation and metabolism. Some functional polymers have the ability to inhibit or to stimulate cell growth while others can alter cell function without a change in growth characteristics. The functional polymers described have possible applications as plasma expanders, non-thrombogenic catheters, non-complement activating surfaces and other applications in oncology, biotechnology and immunochemistry.

ISSN:0920-5063    

DOI:10.1163/156856290X00017

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The effect of glutaraldehyde (GTA) on the course of collagen gel formation was studied by measuring the absorbance against time. It was found that the t1/2of fibril formation decreased with the addition of GTA and reached a minimum at a concentration of 6μl of GTA per g of collagen. For GTA concentrations, [GTA], above this value, t1/2increased again and fibril formation was inhibited at concentrations of about 50-60 μl of GTA per g of collagen. Thermal analysis showed that the denaturation temperature was the highest for the gels formed with [GTA] of 6 μl/g, the transition peak also being the sharpest. At this [GTA], the compressive rigidity of the gels was also the highest. For low [GTA], above and below the optimum value, the fibrils formed had the normal collagen periodicity when observed in the electron microscope. This study shows that collagen gels which find applications as biomaterials can be effectively crosslinked at the gelation stage itself by the addition of low concentrations of GTA.

ISSN:0920-5063    

DOI:10.1163/156856290X00026

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Glass beads were contacted with heparinized human plasma and the adsorbed proteins eluted sequentially with 1 M tris buffer, pH 7.4, and 2% SDS. The proteins in the eluates were analyzed by SDS-polyacrylamide gel electrophoresis and immunoblotting procedures using antisera to 16 common plasma proteins. All sixteen proteins were found to be present in the eluates. The immunoblots provided evidence of contact phase activation although the role of the surface could not be ascertained since some contact activation was apparent in the starting plasma. Evidence was also obtained for the occurrence of complement activation and the fibrinogen Vroman effect on the glass bead surface. Extensive degradation of high molecular weight proteins observed previously in eluates from clinically used hemodialyzers [3] was not observed in the present in vitro plasma experiments, thus supporting the hypothesis that such degradation is due to enzymes liberated in the in vivo experiments by blood cell damage.

ISSN:0920-5063    

DOI:10.1163/156856290X00035

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

An oligopeptide, L-arginyl-glycyl-L-aspartyl-L-serine, having cell attachment activity was synthesized from the respective aminoacids carrying suitable protecting residues, by using carboxymethyl polyethylene glycol (PEG)-modified proteases in organic solvents. Papain, trypsin, and α-chymotrypsin were modified with PEG. Organic solvents used were 1,1,1-trichloroethane, chloroform and chloroform/ ethyl cellosolve (1 : 1) mixture. Identification of the products was done by gel permeation chromatography (GPC) and thin layer chromatography (TLC).

ISSN:0920-5063    

DOI:10.1163/156856290X00044

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

X-ray photoelectron spectroscopy (XPS) and contact angle methods were used to examine the surfaces of an homologous series of poly(ether urethane) (PEU) samples before and after cleaning treatments. Four PEU films with Shore hardnesses varying from 45 to 75 D were studied as well as two commercially available intravenous catheters of related PEUs. The four as received PEU films have similar surface compositions (~79% C, ~17% O, ~2% N, and ~ 2% Si) although they differ in bulk composition. Critical surface tension (γc) values are all similar and high (45-46 dynes/cm). The similarity in the surfaces of the four PEUs, despite the differences in their mechanical properties, demonstrates that surface properties do not necessarily reflect bulk properties. Soap washing and methanol-acetone extraction of the PEU films resulted in surfaces more representative of the bulk compositions of the PEUs. Analysis of the intravenous catheters confirmed that they are lubricated with PDMS, a common practice in the medical device industry. This study documents the value of detailed surface analysis for an enhanced understanding of the surface zone of PEUs. It also illustrates how cleaning protocols can remove labile surface species.

ISSN:0920-5063    

DOI:10.1163/156856290X00053

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The first large scale use of polyether polyurethane elastomers in long term human implants was as insulation for cardiac and neurologic pacing leads. While the performance of these polymers has generally been very good over a 14-year period, several failure mechanisms have been discovered that involve interactions between the devices, materials and the body. One of these is auto-oxidation of soft segment ether through the intermediate action of certain transition metal ions, derived from conductor wires by corrosion processes. Biologically produced oxidants appear to be an accelerating factor. In this study, Pellethane 2363-80A tubing containing conductor coils or mandrels of various metals or controls were implanted in rabbits. Explants were analyzed as a function of implant time by optical and scanning electron microscopy, electron dispersive analysis by X-ray, stress-strain, FTIR, GPC and AA spectrophotometry. Only cobalt produced bulk oxidative degradation while surface damage was found in the presence of cobalt bearing alloys. No evidence of significant auto-oxidation was found in the presence of silver, nickel, chromium, molybdenum, iron, titanium, platinum, 304 stainless steel, glass or empty tubing. The combination of polyether polyurethane and metals (especially those containing cobalt) in an implantable device must be carefully evaluated for biostability prior to human use.

ISSN:0920-5063    

DOI:10.1163/156856290X00062

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor