Application of a phosphorylcholine-based copolymer, poly(MPC-co-BMA) on vial stoppers using a cold plasma deposition process

Coatings are applied to vial stoppers to aid lubricity, reduce leachables and enhance compatibility with protein formulations. However, commonly used polydimethylsiloxane and fluoropolymer coatings have been implicated in particle formation and polymer leaching, which can compromise product quality. This study investigates an innovative aerosol-assisted, cold plasma technique to deposit poly(MPC-co-BMA), which is composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) and butyl methacrylate (BMA) as an alternative coating on vial stoppers. A factorial design of experiments was used to optimise polymer concentration and plasma deposition parameters. Static water contact angle (WCA) and WCA variability were used to indicate coating presence and uniformity. Process parameters, namely speed, affected coating coverage as indicated by changes in stopper hydrophobicity. Analyses using SEM and AFM confirmed conformal coatings. Raman hyperspectral imaging provided an indirect method for mapping coating deposition by monitoring attenuation of the titanium dioxide signal inherent in the stoppers following coating. Poly(MPC-co-BMA) coating compatibility studies with a model bovine serum albumin protein formulation demonstrated comparable performance to commercial polydimethylsiloxane and ethylene tetrafluoroethylene coated stoppers. These findings highlight aerosol-assisted, cold plasma deposition of poly(MPC-co-BMA) as a promising alternative to conventional stopper coatings. Further studies examining the impact of storage and formulation stresses on coating stability and in-depth protein compatibility studies will provide further valuable insights.