HMDC CROSS-LINKING OF BOVINE PERICARDIAL TISSUE - A POTENTIAL ROLE OFTHE SOLVENT ENVIRONMENT IN THE DESIGN OF BIOPROSTHETIC MATERIALS

The need for alternative crosslinking techniques in the processing of bioprosthetic materials is widely recognized. While glutaraldehyde rem ains the most commonly used crosslinking agent in biomaterial applicat ions there is increasing concern as to its biocompatibility-principall y due to its association with enhanced calcification, cytotoxicity, an d undesirable changes in the mechanical properties of bioprosthetic ma terials. Hexamethylene diisocyanate (HMDC), like glutaraldehyde, is a bifunctional molecule which covalently bonds with amino groups of lysi ne residues to form covalent crosslinks. Evidence within the literatur e indicates HMDC-treated materials are less cytotoxic than glutaraldeh yde-treated materials; however, there is limited characterization of t he material properties of HMDC-treated tissue. This study uses a multi -disciplined approach to characterize the mechanical, thermal, and bio chemical properties of HMDC-treated bovine pericardial tissue. Further , to facilitate stabilization of the HMDC reagent, non-aqueous solvent environments were investigated. HMDC treatment produced changes in me chanical properties, denaturation temperature, and enzymatic resistanc e consistent with crosslinking similar to that seen in glutaraldehyde treated tissue. The significantly lower extensibility and stiffness ob served under low stresses may be attributed to the effect of the 2-pro panol solvent environment during crosslinking. While the overall accep tability of HMDC as a crosslinking agent for biomaterial applications remains unclear, it appears to be an interesting alternative to glutar aldehyde with many similar features.