l-DOPA-Based Polymer Coatings via Oxidative Radical Polymerization and Their Antifouling Applications

Bioinspired coatings that mimic the adhesive properties of mussels have received considerable attention for surface modification applications. While polydopamine chemistry has been widely used to develop functional coatings, 3,4-dihydroxyphenyl-l-alanine (l-DOPA), a key component of mussel adhesive proteins, has received less attention because, compared to dopamine, it is relatively difficult to form effective coatings on solid substrates in mildly alkaline solutions. Although several methods have been explored to improve the efficiency of l-DOPA coatings, there is still a need to expand the l-DOPA-based surface chemistry. Herein, we report a simple yet efficient approach to forming poly(l-DOPA)/polymer coatings via radical polymerization with various acrylic monomers. In this one-step, dip-coating process, free radicals generated by the oxidation of l-DOPA either coupled to form poly(l-DOPA) or initiated the polymerization of the acrylic monomers, resulting in polymer coatings on a wide range of substrates. The feasibility of this coating process was confirmed by ellipsometry, contact angle goniometry, X-ray photoelectron spectroscopy, and atomic force microscopy. As a potential application, the antifouling properties of the poly(l-DOPA)/poly(oligo(ethylene glycol) methacrylate) coatings were investigated against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), showing a significant reduction in bacterial adhesion. We think that this study broadens the scope of l-DOPA-based surface chemistry and provides a new avenue for the development of biomimetic functional coatings in materials science and surface engineering.