Effect of ageing and sterilization on plasma multilayer system

Single and coupled effects of sterilization (autoclaving and electron beam) and ageing of plasma polymer multilayer coating on polypropylene mesh are studied. The multilayer system consists in silver nanoparticles entrapped between two maleic anhydride plasma polymer layers and acts as a mechano-sensitive antibacterial reservoir. Tensile strength generates cracks within the plasma polymer overlayer which might be used as diffusive channels for Ag+ species. Changes in surface and bulk properties are followed by SEM, TEM, XPS and antibacterial assays. Whilst autoclave treatment influences surface structure unfavorably, electron beam irradiation with dose of 25 kGy does not induce surface physical or topographical changes. However, electron beam sterilization induces changes in chemistry of the surface causing a decrease in O/C elemental concentration ratio. The surface shows better antibacterial efficiency towards planktonic bacteria after electron beam sterilization and more surprisingly, the combination of electron beam sterilization and ageing has beneficial effect on final properties of the material under stretching.