Crosslink formation in porcine valves stabilized by dye-mediated photooxidation

Bovine pericardial and porcine valve materials stabilized by dye-mediated p hotooxidation have shown potential for bioprosthetic valve use. Previously, in vitro and in vivo stability of these materials was demonstrated through enzymatic, chemical, extraction, rat subcutaneous, and functional challeng es. Here, we examine the stability of photooxidized porcine aortic valves t hrough amino acid, crosslink, and hydrothermal isometric tension analysis. Photooxidation reduced intact histidine residues from 17.0 to 0 residues pe r 1000, indicating the photooxidative alteration of this amino acid. Diphen yl borinic acid-derivitized hydrolyzates of proteins were separated by high -performance liquid chromatography, which identified several amino acid cro sslinks that appeared with photooxidation that were absent in untreated con trols. Thermal relaxation analysis indicated a significantly higher (p < 0. 0002) thermal stability for photooxidized porcine cusps than that of untrea ted controls, with mean relaxation times for untreated cusps of 14,000 +/- 4650 versus 22,900 +/- 2480 s for photooxidized cusps. In summary, porcine aortic valve tissue treated by dye-mediated photooxidation contains new che mical species and exhibits properties consistent with intermolecular crossl ink formation, which explain the increased biostability of this material an d its potential for use in bioprosthetic devices. (C) 2001 John Wiley & Son s, Inc.