title: Optimization of diamine bridges in glutaraldehyde treated bioprosthetic aortic wall tissue.
abstract: OBJECTIVE
  Bioprosthetic calcification can be significantly mitigated by both increased concentrations of glutaraldehyde (GA) and the introduction of diamine (DA) bridges. The purpose of the present study was to evaluate whether an optimal effect of DA-enhanced fixation can be achieved by titration of dialdehyde and diamine concentrations.
  
  
  METHODS
  Porcine aortic roots were fixed at 0.05% GA (under-fixation) or 0.2% GA and 0.7% GA (commercial fixation). An interim step of DA treatment (L-Lysine; 0, 25, 50 or 100 mM; 37 degrees C; 2 days) was followed by completion of the GA fixation (37 degrees C; 5 days). Aortic wall coupons (12 mm) were punched out and implanted subcutaneously into seven-week old Long-Evans rats for 60 days. Calcium content was assessed by atomic absorption spectroscopy and histology.
  
  
  RESULTS
  Increasing the L-Lysine concentrations beyond 25 mM was essential to achieve the anti-calcific effect of DA-enhanced fixation. This effect was proportional to the GA concentrations applied. Compared to non-enhanced GA fixation (0 mM DA), calcification increased by 17.4% (p = 0.2114) in 0.05% fixed tissue but decreased by 32.0% (p < 0.0001) and 45.1% (p < 0.0002) in 0.2% and 0.7% GA, respectively, when the DA concentration was 100 mM. Histologically the extent, but not the pattern of calcification, was affected.
  
  
  CONCLUSIONS
  The calcium mitigating effect of diamine-treatment as an interim step of glutaraldehyde fixation is proportional to the GA concentration applied. Within commercial 0.7% GA fixation 100 mM DA has the potential to practically halve aortic wall calcification.
authors.affiliation: Department of Cardiothoracic Surgery, Cape Heart Centre, University of Cape Town, South Africa.
authors.forename: Paul
authors.initials: P
authors.lastname: Huma
authors.forename: Deon
authors.initials: D
authors.lastname: Bezuidenhout
authors.forename: Mark
authors.initials: M
authors.lastname: Torrianni
authors.forename: Marc
authors.initials: M
authors.lastname: Hendriks
authors.forename: Peter
authors.initials: P
authors.lastname: Zilla
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000637:transplantation; D001705:Bioprosthesis; D002114:Calcinosis / Q000517:prevention & control; D002118:Calcium / Q000378:metabolism; D003959:Diamines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005404:Fixatives / Q000494:pharmacology; D005976:Glutaral / Q000494:pharmacology*; D006350:Heart Valve Prosthesis; D008239:Lysine / Q000737:chemistry / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D013054:Spectrophotometry, Atomic; D013552:Swine; D014180:Transplantation
chemical_list: D003959:Diamines; D005404:Fixatives; D008239:Lysine; D002118:Calcium; D005976:Glutaral