Heparinized poly(vinyl alcohol)--small intestinal submucosa composite membrane for coronary covered stents

To develop a novel coating material for coronary covered stents, we prepared a kind of composite membrane which contains polyvinyl alcohol (PVA) and porcine small intestinal submucosa (SIS) powders crosslinked and heparinized by N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The amount of immobilized heparin increased with increasing ratios of EDC:heparin, and the maximum amount was approximately 60 microg heparin per milligram SIS powder at a weight ratio of EDC:heparin of 2. Uniaxial tensile and balloon inflation testing suggested that the composite membrane crosslinked by lower EDC concentration is more flexible and elastic. The clotting time (APTT and PT) of the heparinized PVA-SIS membrane was longer than that of the unheparinized membrane. The number of adherent platelets on the heparinized PVA-SIS composite membrane was about 25% of the unheparininzed, and there was no sign of accumulation and almost no pseudopodium was observed. The endothelial cells were amicable with the heparinized and unheparinized PVA-SIS composite membranes. In in vivo implantation tests, we observed a thin capsule formed by several layers of fibroblasts surrounding the implants. These results showed that the heparinized PVA-SIS composite membrane has potential biomechanical and biological properties as a coating material for coronary covered stent.