Composition-dependent wettability of nature-inspired homo poly(amino acid) coating and its influences on bacterial adhesion

A variety of natural proteins have shown anti-adhesive functionality against the non-specific adsorption by proteins and bacteria. A deep understanding of the contribution of amino acid composition to the antifouling performance of a natural protein is crucial for engineering a protein-based coating layer. Herein, we synthesized five types of homo poly(amino acid)s via the ring-opening polymerization of alpha-amino acid N-carboxy anhydride (NCA) to include exclusively one type of amino acid from lysine (K), glutamic acid (E), tyrosine (Y), alanine (A), and phenylalanine (F). Homo poly(amino acid)s were covalently immobilized on the surfaces of quartz and polyurethane (PU), respectively. The amino acid composition effects on the wetting and anti-bacterial adhesion of a homo poly(amino acid) coating layer were evaluated. We found that the wettability of homo poly(amino acid) coating layers exhibited a dependence on the intrinsic properties of amino acid side-chain, such as the hydration free energy and dipole moment of side-chain. The activity of a homo poly(amino acid) coating layer against bacterial adsorption was found to be independent of the wetting property of the amino acid side-chain. Our findings are different from the conventional opinion that the hydration property of a material surface coating layer correlates to its anti-bacterial functionality, emphasizing the complexity of the amino acid composition contribution to the activity against the non-specific adsorption of bacteria for a protein-mimicking system.

Automated summary

The study found that the wetting and anti-bacterial adhesion of a homo poly(amino acid) coating layer were affected by the amino acid composition, but the anti-bacterial adhesion activity was not necessarily related to the wetting property of the amino acid side-chain.