Low-temperature argon and ammonia plasma treatment of poly-3-hydroxybutyrate films: Surface topography and chemistry changes affect fibroblast cells in vitro

Poly-3-hydroxybutyrate (PHB) films were plasma-treated using pure NH3, pure Ar or mixtures of the two different proportions (20%, 30%, 40%, 50%, 70% NH3 in Ar). Surface chemistry and surface topography changes of PHB films were observed after plasma processing in all plasma regimes. The XPS results confirmed the absence of chemical modification in the case of pure Ar plasma treatment. Nitrogen-containing groups (e.g., N-C[dbnd]O) were detected on the surfaces of P3HB films treated with NH3-containing plasma. The surfaces of the untreated P3HB films were hydrophobic, and plasma treatment turned the surfaces hydrophilic, irrespective of the treatment. A significant decrease in the contact angle and an increase in the free surface energy were observed. An insignificant surface ageing effect was observed when P3HB samples were exposed to air for 10 days. In NIH 3T3 mice fibroblast cells, cell adhesion was significantly improved after plasma treatment in an Ar atmosphere, which is likely related to the fact that there was a surface x potential of 88.6 mV at neutral pH, causing a cleavage of the polymer chains and an increase in surface roughness.