Fixation of bioprosthetic tissues with monofunctional and multifunctional polyepoxy compounds

Collagen from a native tissue is fixed with a polyepoxy compound (PC) for use as a new biologic prosthetic material. Prior studies have shown that this biomaterial has comparable properties with collagen fixed with glutaraldehyde (GA), and thus has great promise for biomedical applications. A prior kinetic study indicated that the reaction between the functional groups of collagen and the multifunctional epoxy EX‐313 is a 2.5th‐order reaction. The purpose of this study was to understand the mechanism of the amino acid‐PC reactions in a fixation process. Bovine arteries were fixed with a monofunctional PC (EX‐313) and a multifunctional PC (EX‐313) as a function of fixation time. A sequential fixation with a second fixative was used to identify the available remaining reactive sites from a prior fixation. The denaturation temperature (Td) was measured on each sample. Because the denaturation temperature is a direct indication of crosslinking of individual amino acids with the fixative, the increase in Td of a subsequent fixation may be indicative of the available remaining amino acids. The fixation index was measured on each sample to reflect the increase of fixation completion in a sequential fixation process. The fixation index and crosslink data also revealed that the reactive amino acids for EX‐131 and EX‐131 may not be exactly the same. The data in this study suggest that a monofunctional fixative can pre‐react with the amino acids of collagen to effectively block further fixation of collagen with a second fixative. This amino acid masking may be associated with collagen branching. Collagen branching and its effect on denaturation temperature are described. © 1994 John Wiley & Sons, Inc.