Plasma modification of chitosan/hydroxyapatite films in a DC discharge: surface properties and interaction with fibroblasts

The development of technology for modifying polymer materials using cold plasma is an urgent task, as traditional chemical etching leaves a toxic trace that can harm cell viability. The purpose of this work is to modify the surface of composite films composed of chitosan and hydroxyapatite, using direct current (DC) plasma, to enhance the proliferation activity of human fibroblasts on these materials. The film modifications were evaluated using scanning electron microscopy (SEM), contact angle wetting (WCA), infrared spectroscopy (IR) and mass loss analysis. Biocompatibility of the composite films was assessed by the MTT method. Plasma treatment of films in air and argon for 1 min increases the free surface energy. After plasma treatment, the main characteristic oscillation bands change, which indicates the simultaneous destruction of the chitosan polymer chain with the rupture of the O-glycoside bond and the formation of new C-OH bonds. Approximately 1.5-2% of the mass of the initial film is etched in 1 min, after 1 min the etching rate slows down and reaches 3-3.5% for air and 1.8–2.1% for argon during 4-minute processing. The results of the SEM show that after treatment in air and argon plasma, the morphology of the studied films changes and resembles cells. DC plasma modification of the CS + HA composite film increased the proliferation activity fibroblast by 23% within 2 min in air and by 4 min in argon atmosphere.