Poly(oxanorbornene)-Based Polyzwitterions with Systematically Increasing Hydrophobicity: Synthesis, Physical Characterization, and Biological Properties

Surfaces coated with polyzwitterions are known to resist protein adhesion and to be generally bio-inert. In recent reports, several polyzwitterionic coatings with carboxylate groups and intrinsic antimicrobial activity due to the pH-responsivity of that group are described, but the design rules to obtain such activity remain unclear. Therefore, in this work, a set of surface-attached polyzwitterions with carboxylate groups and varying alkyl residues is studied. The gradually increasing hydrophobicity of these surfaces (verified by contact angle and swellability measurements) has an impact on their biological properties. Hydrophilic surfaces (polyzwitterions bearing short alkyl residues) behave like "classical" polyzwitterions: they repel proteins and human cells and are non-toxic to bacteria. The more hydrophobic polyzwitterionic surfaces are protein-adhesive, cell-toxic, and can kill bacteria. This indicates that the hydrophobicity of polyzwitterionic surfaces needs to be balanced precisely to combine protein-repellency and antimicrobial activity in a single material.