Influence of Coating Time on Immobilization of Chlorhexidine on Polydopamine Grafted Stainless Steel 316L: Characterization, Adsorption and Cytotoxicity Analyses

Chlorhexidine (CHX) has a broad antimicrobial range. The immobilization of CHX on a polydopamine (PDA) layer may acts as an antibacterial coating on medical grade stainless steel (SS316L). In this study, the immobilization of CHX on PDA grafted SS316L was performed at different immersion times (3, 6, 9, 12, 24 and 48 hours). The samples were subjected to ATR-FTIR and AFM analyses, adsorption test and cytotoxicity test. The immobilization of CHX at 24 hours produced a stable CHX coating on the PDA layer as evidenced by prominent indicator of CHX long hydrocarbon chain in the FTIR spectra. The CHX coating has higher surface roughness due to CHX aggregation and several protrusions on the grafted PDA layer. Longer immersion time in the CHX salt solution led to high diffusivity rate of solubilized CHX which cause higher absorptivity of CHX on the PDA grafted SS316L. While, the viability study indicated no significant cytotoxicity on osteoblast cells for all time points. The immobilization of CHX on the PDA layer at 24 hours contributed to a stable coating with acceptable cytotoxicity range which could be utilized in the development of an antibacterial coating on metallic implants.