Is Gamma Irradiation as a Secondary Sterilization Procedure Required for Decellularized Xenogenic Tissue Material?

Biological tissues for clinical use typically require gamma irradiation to achieve targeted sterility assurance level (SAL). Gamma radiation produces deleterious changes to physical and surface properties of tissues. In this study, we evaluate the requirement of gamma irradiation as a secondary sterilization procedure by comparing it with non-irradiated chemically treated xenograft tissues. Sixty four bovine pericardia (BP) were decellularized and subjected to nonconventional (glutaraldehyde free) cross-linking. Xenograft samples were screened for bacterial and fungal contaminations both at pre- and post-processing stages, after cross-linking and preservation. Microbial evaluations performed revealed that the xenografts were rendered 'microbe free' by subjecting to a new multistaged decellularization technique and cross-linking. Five of these cross-linked tissues were subjected to gamma irradiation as recommended by IAEC and were tested for surface and mechanical properties to understand the ultrastructure, surface and bulk properties. Surface tension and thrombogenicity parameters were also evaluated. Gamma-irradiated specimen showed reduced physical and mechanical properties of these xenogenic tissues significantly along with biological property. Validation and analysis led us to conclude that this microbe-free decellularization method and subsequent processing for xenogenic tissues is a viable alternative for clinical usage without the deleterious secondary sterilization using gamma irradiation.