Substrate independent coating formation and anti-biofouling performance improvement of mussel inspired polydopamine

Mussel inspired polydopamine (PDA) coating has been proven to be a simple and effective method for surface modification of biomaterials. However, the adhesive functional groups remaining on the surface of PDA coating may promote the attachment of nonspecific proteins and microorganisms and hinder anti-biofouling performance. In this study, the PDA coating formation process is monitored in real-time by a sensitive surface plasmon resonance (SPR) technique at different pH values, initial dopamine concentrations and deposition times. The coating morphology is observed by atomic force microscopy (AFM). Nonspecific protein adsorption, platelet and fibroblast cell adhesion, as well as bacteria attachment on the PDA coatings of different thicknesses are measured to evaluate their anti-biofouling performance. Thickness-dependent biofouling of the PDA coatings is demonstrated by the accumulation of adhesive functional groups within the PDA matrix. In order to reduce the biofouling, we treat the PDA coating by FeCl₃ coordination, NaIO₄ oxidation, heating in air and grafting with a phosphorylcholine copolymer bearing active ester groups. The modified surfaces are characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy measurements. Interestingly, all the treatments help to resist protein adsorption significantly. More excitingly, the simple grafting strategy with a phosphorylcholine copolymer can resist more than 99% of platelet, fibroblast, and bacteria cell attachment, 98% of bovine serum albumin and 95% of bovine plasma fibrinogen adsorption on the PDA coating. These results may find applications in the vast area of surface antifouling, especially for most biomedical devices.