Surfaces for hearts: Establishing the optimum plasma surface engineering methodology on polystyrene for cardiac cell engineering

Plasma surface modification is a popular method for improving cell culture on surfaces, and polystyrene (PS) is literature's material of choice. This study identifies the optimum plasma treatment for promoting normal cardiac cell behaviour during culture. PS slides were plasma-treated with O2, N2, O2 + N2 and Ar + N2 for 20 and 30 min in a reactive ion etcher (RIE). SEM reveals that O2 and O2 + N2 plasmas create dual scale roughness, N2 plasma creates oval-shaped structures, while Ar + N2 exhibits no topography. Evaluation by XPS reveals an increase in the atomic percentage of oxygen for all treatments. Contact angle measurements agree as all treatments lead to hydrophilisation, with N2 samples exhibiting long-term stability. Two sources of cells were used to identify the optimum plasma treatment for cardiac cell culture on PS. H9c2 cells exhibit optimal behaviour with N2 and N2 + Ar regarding viability, morphology, and focal adhesion contact. The same was observed for primary cardiomyocytes on N2 samples. For purified cardiomyocytes, immunofluorescence revealed well-organised sarcomeric structure on N2 samples, exhibiting clear improvement compared to control. SEM validated these findings, as cardiomyocytes on N2-treated PS exhibited physiological, elongated shape. These findings provide solid evidence that the optimum treatment for PS is the use of N2 plasma.