Stimulus-Responsive Polyelectrolyte Surfaces: Switching Surface Properties from Polycationic/Antimicrobial to Polyzwitterionic/Protein-Repellent

Abstract

Surfaces coated with polyzwitterions are most well-known for their ability to resist protein adsorption. In this article, a surface-attached hydrophobically modified poly(carboxybetaine) is presented. When protonated by changes of the pH of the surrounding medium, this protein-repellent polyzwitterion switches to a polycationic state in which it is antimicrobially active and protein-adhesive. The pH range in which these two states exist are recorded by zeta potential measurements. Adsorption studies at different pH values (monitored by surface plasmon resonance spectroscopy) confirm that the adhesion of protein is pH dependent and reversible, that is, protein can be released upon a pH change from pH 3 to pH 7.4. At physiological pH, the poly(carboxyzwitterion) is antimicrobially active, presumably because it becomes protonated by bacterial metabolites during the antimicrobial activity assay. Stability studies confirm that the here presented material is storage-stable, yet hydrolyses after longer incubation in aqueous media.