Zwitterionic polymers are generally viewed as a new class of nonfouling materials. Unlike their poly(ethylene glycol) (PEG) counterparts, zwitterionic polymers have a broader chemical diversity and greater freedom for molecular design. In this Minireview, we highlight recent microbiological applications of zwitterionic polymers and their derivatives, with an emphasis on several unique molecular strategies to integrate antimicrobial and nonfouling properties. We will also discuss our insights into the bacterial nonfouling performance of zwitterionic polymers and one example of engineering zwitterionic polymer derivatives for antimicrobial wound-dressing applications.

Attack or defend! A smart polymer surface has two reversibly switchable equilibrium states, a cationic N,N-dimethyl-2-morpholinone (CB-Ring) and a zwitterionic carboxy betaine (CB-OH). CB-Ring will kill bacteria upon contact under dry conditions, whereas CB-OH will release the previously attached and dead bacteria and further resist adhesion of bacteria under wet conditions.

Zwitterionic materials have shown their excellent performance in many biological and chemical applications. Zwitterionic materials possess moieties that own both cationic and anionic groups. The associations among zwitterionic moieties through electrostatic interactions play an important role in properties of zwitterionic materials. However, the relationship between the molecular structures and associations of zwitterionic moieties are still not well understood. This work compared thermal- and salt-responsive behaviors of sulfobetaine and carboxybetaine polymers by examining their rheological properties as a function of temperature and their hydrodynamic sizes as a function of salt concentration. Results showed that carboxybetaine polymers do not exhibit stimuli responses as expected from the antipolyelectrolyte behavior of zwitterionic polymers as observed in sulfobetaine polymers. We studied and compared the associations among zwitterionic moieties in these two zwitterionic polymers using molecular dynamic simulations. Simulation results show that the charge-density difference between cationic and anionic groups determines the associations among zwitterionic moieties, which are responsible for different stimuli responses of carboxybetaine and sulfobetaine polymers.

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This work reports a thermoresponsive multifunctional wound dressing hydrogel based on ABA triblock copolymers synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. The inner B block consists of a positively‐charged hydrolysable betaine ester loaded with an antimicrobial drug as its counter ion and the B block is flanked by two outer A blocks of thermoresponsive poly (N‐isopropylacrylamide) (PNIPAM). A solution containing the triblock copolymers can be applied to wound sites and immediately turns into a physical gel at the body temperature. This wound dressing can reduce the risk of wound infection by releasing small‐molecular‐weight antimicrobial drug and facilitate the attachment of mammalian cells during tissue regeneration through its positive surface charge. The cationic betaine ester can then hydrolyze at the wound site to its zwitterionic form, which is known to be biocompatible and nonsticky. The thermoresponsive in situ gelation feature along with controlled drug release, enhanced tissue–hydrogel interactions as well as long‐term biocompatibility make this hydrogel a very promising material for antimicrobial wound dressing applications.