Effects of heparin immobilization on the surface characteristics of a biological tissue fixed with a naturally occurring crosslinking agent (genipin): an in vitro study

Heparinized biomaterials have been used to manufacture blood-contacting pro stheses. The present study was intended to characterize the surface propert ies of a genipin-fixed biological tissue immobilized with heparin using the methods of ionic binding (the /h-i tissue) or covalent binding via multi-p oint attachment (the /h-m tissue) or end-point attachment (the /h-e tissue) . The surface characteristics of test tissues evaluated were water contact angle, surface tension, protein adsorption, platelet adhesion, and cellular compatibility. Nonheparinized and the glutaraldehyde-fixed counterparts we re used as controls. It was found that immobilization of heparin on the glu taraldehyde- and genipin-fixed tissues increased their hydrophilicity and s urface tension and suppressed their mole ratio of adsorbed fibrinogen to ad sorbed albumin and the amount of platelets adhered. Among the heparinized t issues, the /h-m tissue was more hydrophobic and had a higher mole ratio of adsorbed fibrinogen to adsorbed albumin and a greater amount of platelets adhered than the /h-i and /h-e tissues. In general, the surface characteris tics of the /h-i tissue were comparable to the /h-e tissue. However, it is known that the ionically immobilized heparin may be displaced from the surf ace by an ion-exchange mechanism when exposed to blood. There were no signi ficant differences in hydrophilicity, surface tension, the mole ratio of ad sorbed fibrinogen to adsorbed albumin, and the amount of platelet adhesion between the glutaraldehyde- and genipin-fixed tissues in comparison with th eir respective counterparts. However, the cellular compatibility of the gen ipin-fixed tissues with or without heparinization was significantly superio r to its glutaraldehyde-fixed counterparts. (C) 2001 Elsevier Science Ltd. All rights reserved.