DEGRADATION POTENTIAL OF BIOLOGICAL TISSUES FIXED WITH VARIOUS FIXATIVES - AN IN-VITRO STUDY

The purpose of this study was to investigate the in vitro degradation potential of porcine pericardia fixed with various aldehyde or epoxy c ompound (EC) fixatives, using bacterial collagenase and pronase. The f ixatives investigated were formaldehyde (FA), glutaraldehyde (GA), mon ofunctional EC (EX-131), and multifunctional ECs (EX-810, EX-313, and EX-512). Fresh porcine pericardium was used as a control. The test sam ples were well immersed in a 20-U/mt collagenase solution or a 10-U/mL pronase solution and incubated at 37 degrees C at PH 7.5 for 24 h. Th e extent of degradation of each test sample was determined by measurin g its increment in free amino group content and changes in collagen st ructure, denaturation temperature, and tensile stress after degradatio n. In gereral, the extent of tissue degradation with pronase was more notable than with collagenase. As observed with fresh tissue, the EX-1 31 EC fixed tissue radically disintegrated after either collagenase or pronase degradation, whereas the other test samples remained intact. The reason for this may reside in the more random molecular packing of the EX-131 EC-fixed tissue, which led to some loss in its helical int egrity. This made penetration of enzymes into biological tissue easier . Of the multifunctional EC test groups, tissues fixed with tetrafunct ional EC (EX-521) or trifunctional EC (EX-313) had relatively better r esistance to degradation than those fixed with bifunctional EC (EX-810 ). The extent of degradation for the EX-313 or EX-512 EC fixed tissues was similar to that observed for the FA- or GA-fixed tissues. The res ults of this study indicated that the biological tissue fixed with mon ofunctional EC (EX-131) cannot resist bacterial collagenase or pronase degradation. However, resistance to deg radation of the multifunction al EC (EX-313 or EX-152)-fixed tissues was comparable to that of the a ldehyde (FA or GA)fixed tissues. Therefore, of various EC fixatives, t he EC with a greater number of functional groups should be chosen for tissue fixation to increase its resistance to enzymatic degradation. ( C) 1997 John Wiley & Sons, Inc.