Comparison of haemocompatibility improvement of four polymeric biomaterials by two heparinization techniques.

Two surface heparinization procedures, introduced by Bamford and Al-Lamee (Polymer 22 (1996) 4885; 13 (1994) 2844) and Seifert et al. (J. Mater. Sci.: Mater. Med. 7 (1996) 465), respectively, were applied to four commercially available biomaterials (silicone rubber, polyethylene, polypropylene and polyvinylchloride) in order to compare their efficiency in improving haemocompatibility. The indirect method (Bamford and Al-Lamee) produced a much better heparinization yield-10.5% maximum, compared to the direct one (Seifert et al.), of only 0.20% maximum. Both methods provided a better response of the heparinized biomaterials compared to the uncoated ones in terms of platelet retention and a significantly better response in terms of activation of the coagulation system, suggesting that heparin molecules remained biologically functional in both cases. The results were particularly interesting in the case of polyvinylchloride where the maximum immobilization yield was obtained by the indirect method resulting also to a pronounced haemocompatibility improvement. Scanning electron microscopy studies confirmed adhered platelet morphology whereas atomic force microscopy was used to examine surface morphology of heparinized and reference materials surface.