Optimization and Antibacterial Response of N-Halamine Coatings Based on Polydopamine

Due to the ability of microorganisms to first adhere to a material surface and then to lead to the formation of a biofilm, it is essential to develop surfaces that have antimicrobial properties. It is well known that N-halamine coatings allow us to prevent or minimize such phenomena. In the present work, various polydopamine (PDA) coatings containing chloramine functions were studied. In fact, three PDA-based films were formed by the simple immersion of a gold substrate in a dopamine solution, either at pH 8 in the presence or not of polyethyleneimine (PEI), or at pH 5 in the presence of periodate as an oxidant. These films were characterized by polarization modulation reflection absorption infrared spectroscopy and X-ray photoelectron spectroscopy analyses, and by scanning electron microscopy observations. The chlorination of these PDA films was performed by their immersion in a sodium hypochlorite aqueous solution, in order to immobilize Cl(+I) into the (co)polymers (PDA or PDA-PEI). Finally, antibacterial assays towards the Gram-negative bacteria Escherichia coli (E. coli) and the Gram-positive bacteria Staphylococcus epidermidis (S. epidermidis) were conducted to compare the bactericidal properties of these three N-halamine coatings. Regardless of the bacteria tested, the PDA coating with the best antibacterial properties is the coating obtained using periodate.