Antimicrobial zwitterionic hydrogel coatings for kidney disease-associated catheters: current challenges and advances

Zwitterionic hydrogel coatings comprise three-dimensional networks of zwitterionic polymers that bear balanced anionic and cationic groups. These coatings exhibit superior hydration capacity, high drug-loading efficiency, excellent biocompatibility, and remarkable salt resistance. As a result, they have demonstrated significant potential for antimicrobial biomedical applications, i.e., wound dressings, drug delivery, and modifications of medical catheters and implants. In particular, in the context of kidney disease-associated catheters, zwitterionic hydrogel coatings display dual antimicrobial mechanisms: bacterial-repelling and bactericidal effects. Special emphasis is placed on smart coatings, including pH-responsive degradation and drug release, charge-switchable zwitterionic monomer applications, and self-healing functionalities. However, the mechanical properties of zwitterionic hydrogel coatings remain suboptimal. This limitation has been effectively mitigated through strategies consisting of crosslinking optimization, monomer modification to create triazole-zwitterionic hydrogels, and the development of multiple crosslinked zwitterionic hydrogel networks. Additionally, this critical review provides a detailed introduction to recently developed versatile adhesion methods, such as mussel-inspired chemistry, interfacial interpenetration and polycation-reinforced surface bridging strategies, for achieving robust hydrogel integration of hydrogels on catheters. Finally, key prospects for advancing catheter coating design toward clinical translation are outlined.