Reversibly Charge-Switching Polyzwitterionic/Polycationic Coatings for Biomedical Applications: Optimizing the Molecular Structure for Improved Stability.

Materials that can be switched between a polycationic/antimicrobial and a polyzwitterionic/protein-repellent state have important applications, e.g., as biofilm-reducing coatings in medical devices. However, the lack of stability under storage and application conditions so far restricts the lifetime and efficiency of such materials. In this work, a polynorbornene-based polycarboxybetaine with an optimized molecular structure for improved hydrolytic stability is presented. The polymer is fully characterized on the molecular level. Surface-attached polymer networks are obtained by spin-coating and UV cross-linking. These coatings are highly uniform and demonstrate charge-switching in zeta-potential studies. Storage stability in the dry state, as well as in aqueous systems at pH 4.5 and 7.4 for 28 days, is demonstrated. At pH 8, hydrolytic degradation is observed. Overall, the materials are substantially more stable than the corresponding ester-based systems.