Plasma treatment of pMDI canisters reduces dispersive and acidic surface energy

The performance of pressurised metered-dose inhalers (pMDIs) has been a focus since the 1950s, particularly addressing drug degradation and inconsistent dosing. This study examined aluminium pMDI canisters treated with plasma-enhanced chemical vapor deposition (PECVD), applying a fluorocarbon polymer (FCP) coating. PECVD offers a more environmentally friendly alternative to traditional spray coatings by avoiding harmful solvents and chlorinated primers.<br/><br/>Three types of canister base were examined: Untreated, Plasma 1, and Plasma 2. Both plasma treatments used identical conditions but were applied in different-sized chambers. Optical contact angle measurements of diiodomethane, formamide, and water determined dispersive, acidic, and basic surface energy properties. A total of 2160 measurements were collected across three liquid types, three locations on each canister base, and four replicates. The van Oss, Chaudhury, and Good Equation (vOCG) calculated surface energy, solved through singular value decomposition with Monte Carlo simulation.<br/><br/>Results showed plasma treatment significantly reduced the mean dispersive component of surface energy from 38.79 mJ/m² (95% credible interval (CI): 37.0, 40.1) to 11.08 mJ/m² (95% CI: 10.4, 11.8) and the mean acidic component from 23.2 mJ/m² (95% CI: 20.1, 26.5) to 0.3 mJ/m² (95% CI: 0.1, 0.7), with changes in the mean basic component occurring only in the centre of the base, compared with untreated canisters. Variability in surface energy was also reduced, particularly between central locations, with a small statistically significant difference between Plasma 1 and Plasma 2 only at the edge of the base.<br/><br/>These findings suggest PECVD treatment may reduce drug-surface interactions and surface variability, enhancing pMDI performance and stability while offering a more environmentally sustainable alternative to conventional treatments.