Glutaraldehyde-induced cross-links: A study of model compounds and commercial bioprosthetic valves

Background and aim of the study: The treatment of bioprosthetic tissue rout inely involves the use of glutaraldehyde, although the specific chemistry o f glutaraldehyde fixation is not fully understood. Descriptions of definiti ve work on this reaction using model compounds are limited. The aim of the present study was to increase our understanding of the chemistry involved i n the treatment of collagen-rich tissue with glutaraldehyde. Initially, 6-a minohexanoic acid (6-AHA) was used to model the lysine/hydroxylysine molecu les in collagen before studying the more complex chemistry of the tissue. Methods: The reaction between 0.6% glutaraldehyde and 6-AHA was studied by positive ion electrospray-mass spectroscopy Untreated, locally treated and commercially produced explanted and non-implanted tissue were hydrolyzed un der various conditions and analyzed both directly and after derivatization with 4-chlorophenylhydrazine, 4-bromophenacyl bromide and dansyl chloride b y reverse-phase-high performance liquid chromatography-mass spectrometry. Results: The mass spectral data obtained from the reaction of glutaraldehyd e with 6-AHA showed the presence of alpha,beta unsaturated aldehydes and th eir further condensation products involving Michael reactions of glutaralde hyde, Schiff base cross-links and various cyclization products incorporatin g pyridinium and dihydropyridine ring structures. The only stable cross-lin k detected was an 'anabilysine'-like compound. Similar structures were pres ent in the tissue, and anabilysine was identified by tandem mass spectromet ry. Conclusion: The results from the reaction of glutaraldehyde with 6-AHA agre e with those published previously. The only detectable stable cross-link de finitively identified in treated bioprosthetic tissue was anabilysine. No l ong-chain polymers of glutaraldehyde were detected.