Experimental application of polyvinyl alcohol-silica for small artificial vessels

Polyvinyl alcohol-silica (PVA-SiO2) composite and heparinized PVA-SiO2 were examined in vitro and in vivo as materials to coat artificial vessels to be used for the replacement of small arteries. PVA-SiO2 was observed to prolong coagulation time and on heparinized PVA-SiO2 surfaces no blood coagulation was noticed after a period of two days using the Lee-White and plasma recalcification methods. After placing non-coated and coated surfaces in contact with blood components in vitro and in vivo, the degree of blood component adhesion was greater in non-coated woven Dacron than in PVA-SiO2 coated Dacron. The degree of adhesion was even less in heparinized PVA-SiO2 coated Dacron. Furthermore, artificial vessels made of these 3 types of materials were used to replace parts of the canine abdominal aorta and were removed one and a half years later. Patency rates were as follows: non-coated 2/7, PVA-SiO2-coated 4/7, heparinized PVA-SiO2-coated 8/12. The inner surfaces of these prostheses were observed with light microscopy and scanning electron microscopy. Intima formation was thinner on the PVA-SiO2 composite surfaces than on the control surfaces. Heparin acted as a local anticoagulant and PVA-SiO2 limited intima formation. This report showed that PVA-SiO2 composite coated surfaces can be effective for small artery replacement due to good tissue affinity and anticoagulability.