Sterilization effects on ultrathin film polymer coatings for silicon-based implantable medical devices.

Novel biomaterials for medical device applications must be stable throughout all stages of preparation for surgery, including sterilization. There is a paucity of information on the effects of sterilization on sub-10 nm-thick polymeric surface coatings suitable for silicon-based bioartificial organs. This study explores the effect of five standard sterilization methods on three surface coatings applied to silicon: polyethylene glycol (PEG), poly(sulfobetaine methacrylate) (pSBMA), and poly (2-methacryloyloxyethyl phosphorylcholine) (pMPC). Autoclave, dry heat, hydrogen peroxide (H2 O2 ) plasma, ethylene oxide gas (EtO), and electron beam (E-beam) treated coatings were analyzed to determine possible polymer degradation with sterilization. Poststerilization, there were significant alterations in contact angle, maximum change resulting from H2 O2 (Δ - 14°), autoclave (Δ + 15°), and dry heat (Δ + 23°) treatments for PEG, pSBMA, and pMPC, respectively. Less than 5% coating thickness change was found with autoclave and EtO on PEG-silicon, E-beam on pSBMA-silicon and EtO treatment on pMPC-silicon. H2 O2 treatment resulted in at least 30% decrease in thickness for all coatings. Enzyme-linked immunosorbent assays showed significant protein adsorption increase for pMPC-silicon following all sterilization methods. E-beam on PEG-silicon and dry-heat treatment on pSBMA-silicon exhibited maximum protein adsorption in each coating subset. Overall, the data suggest autoclave and EtO treatments are well-suited for PEG-silicon, while E-beam is best suited for pSBMA-silicon. pMPC-silicon was least impacted by EtO treatment. H2 O2 treatment had a negative effect on all three coatings. These results can be used to determine which surface modifications and sterilization processes to utilize for devices in vivo.