Sterilization modalities for medical devices include ionizing radiation (gamma or electron beam), ethylene oxide (ETO), autoclaving (high temperature), and gas plasma. Gamma and ETO sterilization are the most popular techniques. Gamma has the advantage that devices can be sterilized in conventional packaging, and hidden surfaces in the devices can be reached by gamma. Gamma has the disadvantage that it can chemically alter some materials, such as some polymers, which may result in property changes. ETO does not have the issue with chemical modifications of most materials, but does involve the use of gas-permeable packaging. Additional ETO is a carcinogenic chemical, and residues must be carefully monitored following sterilization. Both ETO and gamma require custom facilities to perform the sterilization, which involves shipping and quarantine times.
Autoclaving and gas plasma can both be done at manufacturer's facilities. Autoclaving is not suitable for most polymeric devices, as the temperatures used would result in device distortion. Gas plasma does not have this issue, but is limited to surface sterilization.
Vaporized peracetic acid (VPA) sterilization is an alternative method to gas plasma. In VPA, the peracetic acid, which is produced by reacting acetic acid with hydrogen peroxide, acts as a strong oxidizer, and is believed to denature protein and oxidize sulfide bonds. It can also disintegrate the cell walls of bacteria. Similar to gas plasma and ETO, VPA is a surface sterilant only. An advantage of VPA over ETO is the lack of toxic compounds. VPA can be safely performed in conventional manufacturing spaces, and requires less time to remove the sterilization by-products compared to ETO.