Simultaneously Antimicrobial, Protein-repellent and Cell-compatible Polyzwitterion Networks: More Insight on Bioactivity and Physical Properties.

A poly(oxanorbornene)-based polyzwitterion with primary ammonium and carboxylate groups () has been reported previously as the first simultaneously antimicrobial and protein-repellent polyzwitterion. Here, additional physical and biological properties of three poly(oxanorbornene)-based polyzwitterions with different functional groups (, the polycarboxybetaine , and the polysulfobetaine ) are compared to understand the molecular origins of this unusual bioactivity. Additionally, the three polyzwitterions and the antimicrobial, polycationic are exposed to proteins, bacteria suspensions, human plasma and serum. These interactions are investigated by surface plasmon resonance spectroscopy. In protein adhesion studies, neither fibrinogen nor lysozyme adhere irreversibly to , yet reversible interaction with lysozyme is observed at pH 7 and 8. In the presence of bivalent cations, reversible fibrinogen adhesion on and is observed, but not on . This might explain why mammalian cells grow on and , but not on . does not show human plasma adhesion, while and have 0.27 and 0.48 ng mm adhered plasma, and even 6.3 ng mm. Both and show strong serum adhesion, while no serum adhered to , and only little to . This could be related to the pH difference between serum and plasma, to which the pH-responsive primary ammonium groups are susceptible, while the permanently charged NR groups are unaffected. Both and showed none or only little bacterial adhesion. is also intrinsically antimicrobial against . and . bacteria and thus is also simultaneously protein-repellent and antimicrobially active. Thus, while the carboxylate groups of and seems to be a prerequisite for the dual antimicrobial activity and protein-repellency, the pH-responsiveness of the primary ammonium group seems to make the molecule vulnerable for protein adhesion in fluids that are slightly out of the physiological range.