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

## TL;DR

This paper introduces a new stable coating material that can switch between antimicrobial and protein-repellent states for biomedical use.

## Contribution

A polycarboxybetaine polymer with improved hydrolytic stability is developed for reversible charge-switching coatings.

## Key findings

- The polymer shows high stability in dry and aqueous conditions at pH 4.5 and 7.4 for 28 days.
- Charge-switching behavior is confirmed through zeta-potential studies.
- The material is more stable than ester-based systems but degrades at pH 8.

## Abstract

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.