A versatile approach to antimicrobial coatings via metal-phenolic networks

This study reports a newly developed approach for an antimicrobial coating using coordination of functional catechol, polyphenols and metal ions in an aqueous solution. Bioinspired zwitterionic sulfobetaine dopamine (SB[sbnd]DA) provides fouling resistance, with tannic acid (TA) and metal ions serving as agents for surface conditioning. Films were formed by adsorption of a metal–phenolic complex network (MPN) on various planar organic and inorganic substrates. Because of its super-hydrophilic and charge-balanced properties, SB[sbnd]DA develops a tightly-bound water layer on top of the complex network to repel nonspecific adsorption. We compare ferrous ion (Fe^II) and ferric ion (Fe^III), estimating their stabilities with phenol groups by measuring the binding constant. Surface hydration of the modified substrates was tested by contact angle goniometer; the surface elemental composition and the chemical states of the modified substrates were confirmed by X-ray photoelectron spectroscopy (XPS). To examine antifouling properties, modified substrates were immersed in solutions containing bacteria or mammalian cells. The adsorbed bacteria and cells were quantified using fluorescence microscopy and cell imaging analysis, showing the good antifouling properties of MPN-assembled zwitterionic coatings. Coatings were applied on various substrates, including silica, metal oxides, and plastics. The results show that zwitterionic SB[sbnd]DA can be coated on different surfaces via assembly of MPN, providing an antimicrobial treatment. This approach for substrate modification offers a facile and environmentally friendly means to realize biocompatible coatings for many types of substrates. The work also provides insight into the construction of hierarchical structures by molecular assembly for functional biointerfaces.