Stabilization and Sterilization of Pericardial Scaffolds by Ultraviolet and Low-Energy Electron Irradiation

Pericardial scaffolds have a wide spectrum of clinical applications ranging from patches for vascular reconstruction and abdominal wall defects to bioprosthetic heart valves. The current gold standard of tissue preparation involves disinfection and cross-linking using glutaraldehyde. However, glutaraldehyde-associated toxicity as well as rapid calcification and premature graft failure represent the major modes of failure.(1) Therefore, a variety of alternative strategies for tissue conservation have been pursued. However, none of those strategies has substituted glutaraldehyde as the method of choice yet. Furthermore, safe sterilization procedures that are nondetrimental to the tissue's functionality are scarce. We have developed a novel procedure to stabilize and sterilize (S) acellular pericardial scaffolds combining photo-initiated ultraviolet cross-linking (U) with low-energy electron irradiation (LEEI). This SULEEI procedure avoids the use of glutaraldehyde and utilizes LEEI as effective sterilization method. A bioburden of 5.1 x 10(5) +/- 4.6 x 10(5) viable bacteria could be successfully inactivated by SULEEI treatment applying a surface dose of 30.6 +/- 2.8 kGy. By challenging high-density polyethylene foil stacks with >10(6) Bacillus pumilus spores in different depths and modeling the dose distribution within the scaffolds, a maximum sample thickness of 175 mu m was determined for successful sterilization. Moreover, SULEEI treatment appeared nondetrimental to the ultimate tensile strength (17.6 +/- 8.6 MPa vs. 17.4 +/- 9.6 MPa) of the scaffolds compared with glutaraldehyde-treated pericardia. Cell number and overall metabolic activity of human endothelial cells were significantly higher on SULEEI-treated pericardia compared with control samples. In contrast, no cell proliferation could be detected on glutaraldehyde-treated pericardia. Thus, the SULEEI procedure may be a promising novel procedure for glutaraldehyde-free tissue preparation for pericardium-based tissue transplants and tissue engineering.