Effect of radiation sterilisation on the structure and antibacterial properties of antimicrobial peptides

Antimicrobial peptides (AMPs) have recently been exploited to fabricate anti-infective medical devices due to their biocompatibility and ability to combat multidrug-resistant bacteria. Modern medical devices should be thoroughly sterilised before use to avoid cross-infection and disease transmission, consequently it is essential to evaluate whether AMPs withstand the sterilisation process or not. In this study, the effect of radiation sterilisation on the structure and properties of AMPs was explored. Fourteen AMPs formed from different monomers with different topologies were synthesised by ring-opening polymerisation of N-carboxyanhydrides. The results of solubility testing showed that the star-shaped AMPs changed from water-soluble to water-insoluble after irradiation, while the solubility of linear AMPs remained unchanged. Matrix-assisted laser desorption/ionisation time of flight mass spectrometry showed that the molecular weight of the linear AMPs underwent minimal changes after irradiation. The results of minimum inhibitory concentration assay also illustrated that radiation sterilisation had little effect on the antibacterial properties of the linear AMPs. Therefore, radiation sterilisation may be a feasible method for the sterilisation of AMPs, which have promising commercial applications in medical devices.