No abstract

Heparin has been chemically combined with a number of plastic surfaces rendering them nonthrombogenic as judged by Lee-White coagulation tests in vitro with human blood. Addition of quaternary ammonium groups to the plastic permitted formation of insoluble complexes with heparin. These heparinized surfaces were essentially nonthrombogenic and adsorb blood proteins to a significantly smaller degree from dilute solution than do the unmodified plastic surfaces. The affinity of the formed blood elements for these modified surfaces is much less than for the unmodified surfaces.

No abstract

A study is reported of the degradation of irradiated methacrylate polymers, the formation and trapping of free radicals, and their electron spin resonance (e.s.r.) spectrum. Several different radicals are apparently formed and it seems necessary to assume that they are formed by different mechanisms. This is also suggested by a number of observations of main chain degradation and the ratio of chain scission to ester removal for several methacrylate polymers. It is probable that several mechanisms of degradation and radical formation are operative and the one which predominates is dependent on the pendant ester structure.

A Fourier transform infrared/attenuated total reflectance technique has been developed to study protein adsorption onto surfaces. The application of this technique to an ex vivo model using a beagle dog as the source of whole, flowing blood is described (currently, high-quality infrared spectra are being collected at 5-s intervals of protein adsorption). This approach has enabled the authors to identify albumin and glycoproteins as the initially adsorbing species, with the subsequent competitive replacement of part of this protein layer with fibrinogen and other proteins. The exact relationship between the pattern of protein adsorption from whole blood and the generation of a thrombus (clot) is not yet clear, but it is hoped that this type of experimental approach will help clarify the relationship.