Development of sterilisation strategies for decellularised peripheral nerve grafts

Peripheral nerve injuries represent one of the leading causes of disability globally; due to limitations of current therapies, there is a clear clinical need for a novel peripheral nerve graft . Decellularised porcine peripheral nerves may represent a suitable material; however, they would require terminal sterilisation prior to use. The main aim of this study was to identify a sterilisation method which minimally impacted upon decellularised nerve extracellular matrix (ECM) structure, biochemical composition, biomechanical properties and biocompatibility. Peracetic acid (PAA) solution 0.1 % (v/v) caused disruption to the structure of the endoneurium and reductions in the intensity of antibody labelling for basement membrane components, particularly collagen IV (with increased severity after a 12 month storage period). Supercritical carbon dioxide (SCCO2) treatment (with an additive solution containing 13.5 - 18.5 % [v/v] PAA and 4.5 - 6 % [v/v] H2O2) under standard conditions induced similar effects to the histioarchitecture and significant alterations to tensile mechanical properties; processing of the tissue whilst submerged in phosphate-buffered saline appeared to protect against such effects. Treatment with gamma radiation (25 – 28 kGy) and E Beam (33 – 37 kGy) mediated retention of the decellularised nerve ECM structure, and changes to the localisation and intensity of labelling for basement membrane components were minimal compared with those observed following treatment with PAA solution or SCCO2 under standard conditions. However, gamma radiation caused the stiffness of the nerves to increase. Contact culture experiments did not yield evidence of cytotoxicity following any of the sterilisation methods; furthermore, the sterilised nerves did not induce any significant changes in the secretion of key cytokines by a murine macrophage cell line. These data indicate that E Beam could be an optimal sterilisation method for use with the decellularised nerves, notwithstanding preliminary results indicating that SCCO2 processing under submerged conditions may enable superior basement membrane preservation.