BIOLOGICAL-MATERIALS FIXED WITH AN EPOXY COMPOUND - COMPARISON OF THEEFFECTS WITH OR WITHOUT IONICALLY BOUND HEPARIN

Biological materials have been used as prosthetic devices such as hear t valves, vascular grafts, and pericardial patches, These biological m aterials have to be fixed with crosslinking reagents and sterilized su bsequently before they can be implanted in humans, Recently, a new cro sslinking reagent, epoxy compound, has been used to fix bioprostheses. In this fixation technique, heparin may be ionically bound on the tis sue surface, It has been shown that the amount of heparin bound to the tissue surface is proportional to the quantity of protamine impregnat ed in the biological tissues, However, it is not known if the impregna tion of protamine will affect the crosslinking density of the biologic al tissues, This study was designed to compare the crosslinking densit ies of the epoxy compound fixed biological tissues with or without hep arinization, Fresh porcine aortic valves procured from a slaughter hou se were first impregnated in various concentrations of protamine sulfa te (0, 0.5, 1.0, or 1.5%) for about 30 min, The porcine aortic valves were then crosslinked in a 4% epoxy compound solution (Denacol(R) EX-3 13), The porcine samples were taken out at various elapsed fixation pe riods: 18, 25, 48, 72, 96, and 120 h. Finally, the crosslinked porcine aortic valves were heparinized in a 0.5% sodium heparin solution for about 1 h. The crosslinking densities of the porcine leaflet and the a ortic wall of each sample were determined by measuring their shrinkage temperatures, It was revealed that the impregnation of various concen trations of protamine did not seem to significantly alter the shrinkag e temperatures of the porcine leaflet and the aortic wall throughout t he entire fixation process (p > 0.05), This indicated that the impregn ation of protamine did not significantly change the crosslinking densi ty of the biological tissues, However, it was found that protamine ten ded to discolor the tissue and to stiffen the porcine leaflet and the aortic wall, Although the impregnation of protamine did not seem to si gnificantly alter the crosslinking density of the epoxy compound fixed biological tissues, the increase of the stiffness of the heparinized tissues may cause concerns in some clinical applications. (C) 1995 Joh n Wiley and Sons, Inc.