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

Abstract

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 × 105 ± 4.6 × 105 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 >106 Bacillus pumilus spores in different depths and modeling the dose distribution within the scaffolds, a maximum sample thickness of 175 μm 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.Impact StatementPericardium-based tissue transplantation is a lifesaving treatment. Commercial glutaraldehyde-treated pericardial tissue exhibits cytotoxicity, which is associated with the accelerated graft failure. Replacement of glutaraldehyde has been suggested to overcome those drawbacks. In this study, we report a toxin-free method that combines tissue stabilization with a terminal sterilization. Our data indicate that the SULEEI procedure, which is part of an issued patent, may be a promising first step toward glutaraldehyde-free pericardium-based tissue transplants. Thus, our results may contribute to improving cardiovascular treatment strategies.

Sterilization and Cross-Linking Combined with Ultraviolet Irradiation and Low-Energy Electron Irradiation Procedure: New Perspectives for Bovine Pericardial Implants in Cardiac Surgery

“…3,29,32,36,37 Mechanical properties such as the ultimate tensile strength, suture retention strength, strain at rupture, and Young's modulus values did not differ in the bovine pericardia treated with the innovative SULEEI strategy when compared with glutaraldehyde-fixed tissues and were comparable to the clinically used patches and a prosthesis. This similarity in mechanical properties is, in part, contrary to the results obtained with porcine pericardium, 31 where Young's modulus was significantly higher for the SULEEI-treated porcine tissue than for glutaraldehyde-fixed tissue. Porcine pericardium is thinner (100-150 µm 31 ) than bovine pericardium (500 µm); therefore, this property may explain the greater similarity of the mechanical parameters of SULEEI-treated and glutaraldehyde-fixed bovine pericardial tissues.…”

“…We recently demonstrated the feasibility of preserving porcine pericardial tissue using the SULEEI procedure. 31 In this study, we applied the SULEEI procedure to bovine pericardium and investigated the biomechanics and histomorphological and cellular aspects of the treated pericardial tissues. This investigation is of major relevance since bovine pericardium is the preferred material for use as biologically derived patches and substitutes in cardiovascular applications.…”

“…In general, the histoarchitecture of the tissue appeared well preserved and in agreement with the literature data and with the results we obtained using porcine pericardia. 10,28,31,41,42 For a more detailed investigation of collagen fiber structure and alignment, as it was shown for SULEEI-treated porcine pericardium, scanning electron microscopy will be used in ongoing studies. 31,48,49 The preservation of SULEEI-treated bovine tissue morphology led to the assumption that the biodegradability and biomechanical behavior of the SULEEI-treated bovine pericardium would be equivalent to that of the clinically available patch material.…”

“…Our recently published pilot study validated and confirmed the suitability of the SULEEI procedure for conserving porcine pericardial tissue in vitro in terms of its mechanical properties and cytocompatibility. 31 Bovine pericardium is the major natural source used in clinical applications; however, bovine and porcine pericardium differ in relevant aspects, including tissue thickness and extracellular matrix composition. 32 Therefore, the aim of this study was to confirm the feasibility of using the SULEEI procedure for the preparation of bovine pericardium.…”

In Vitro Evaluation of Acellular Collagen Matrices Derived from Porcine Pericardium: Influence of the Sterilization Method on Its Biological Properties

“…Sterilization is necessary before the implantation of any biomedical device [ 24 , 25 ]. The ideal sterilization method should avoid significant changes in device properties [ 26 ]. Some sterilization methodologies range from the use of heat and pressure, ionizing radiation (ultraviolet (UV), X-ray, gamma irradiation and E-beam), chemical sterilants (ethylene oxide, hydrogen peroxide and peracetic acid) and, recently, the use of supercritical carbon dioxide and ionized gas plasma [ 24 ].…”