title: Glutaraldehyde-induced cross-links: a study of model compounds and commercial bioprosthetic valves.
abstract: OBJECTIVE
  The treatment of bioprosthetic tissue routinely involves the use of glutaraldehyde, although the specific chemistry of glutaraldehyde fixation is not fully understood. Descriptions of definitive work on this reaction using model compounds are limited. The aim of the present study was to increase our understanding of the chemistry involved in the treatment of collagen-rich tissue with glutaraldehyde. Initially, 6-aminohexanoic acid (6-AHA) was used to model the lysine/hydroxylysine molecules 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 under various conditions and analyzed both directly and after derivatization with 4-chlorophenylhydrazine, 4-bromophenacyl bromide and dansyl chloride by reverse-phase-high performance liquid chromatography-mass spectrometry.
  
  
  RESULTS
  The mass spectral data obtained from the reaction of glutaraldehyde with 6-AHA showed the presence of alpha,beta unsaturated aldehydes and their further condensation products involving Michael reactions of glutaraldehyde, Schiff base cross-links and various cyclization products incorporating pyridinium and dihydropyridine ring structures. The only stable cross-link detected was an 'anabilysine'-like compound. Similar structures were present in the tissue, and anabilysine was identified by tandem mass spectrometry.
  
  
  CONCLUSIONS
  The results from the reaction of glutaraldehyde with 6-AHA agree with those published previously. The only detectable stable cross-link definitively identified in treated bioprosthetic tissue was anabilysine. No long-chain polymers of glutaraldehyde were detected.
authors.affiliation: Human Metabolism and Clinical Biochemistry, University of Sheffield, UK.
authors.forename: L J
authors.initials: LJ
authors.lastname: Southern
authors.forename: H
authors.initials: H
authors.lastname: Hughes
authors.forename: P V
authors.initials: PV
authors.lastname: Lawford
authors.forename: M R
authors.initials: MR
authors.lastname: Clench
authors.forename: N J
authors.initials: NJ
authors.lastname: Manning
mesh_terms: D015119:Aminocaproic Acid; D000818:Animals; D001705:Bioprosthesis; D002417:Cattle; D003094:Collagen / Q000737:chemistry; D003432:Cross-Linking Reagents; D019544:Equipment Failure Analysis; D005404:Fixatives; D005976:Glutaral; D006350:Heart Valve Prosthesis; D006801:Humans; D013058:Mass Spectrometry; D011474:Prosthesis Design; D013329:Structure-Activity Relationship; D013552:Swine
chemical_list: D003432:Cross-Linking Reagents; D005404:Fixatives; D003094:Collagen; D005976:Glutaral; D015119:Aminocaproic Acid