Radio-frequency plasma-induced biocompatibility of polyimide substrates

Abstract

Surfaces of polyimide (PI) sheets were modified using 13.56-MHz radio-frequency discharges to enhance their affinity with fibroblast cells. Physico-chemical analysis of pristine and plasma-treated PI sheets showed different responses against argon (Ar), oxygen (O2), and nitrogen (N2) as the plasma process gases. Overall, hydrophilicity of treated PI surfaces was enhanced, and its surface free energy increased from 53 dyn/cm to at least 73 dyn/ cm. Surface roughness values also increased from 1.3 to 40.8 nm, as demonstrated by atomic force microscopy analyses. Infrared spectral analyses showed a decrease of imide functional group peak intensities on plasma exposure, corresponding to chemical surface structural changes. In addition, plasma-treated surfaces significantly increased cell adhesion and proliferation compared to pristine samples. N2-containing plasma exhibited the greatest increase among the test gases, due to the possible inclusion of N2-based functional groups that enhance biochemical affinity of fibroblast cells.