Zwitterionicpolymers are polymeric materials that are electrically neutral as a whole and contain both anionic and cationic groups on the side chain of the same monomer. Due to their strong hydration ability and good biocompatibility, among other characteristics,zwitterionicpolymers have been widely studied and applied in biomedical and other fields. Since Alfrey et al. first reported the synthesis ofzwitterionicpolymers in 1950, their unique molecular structures and physicochemical properties have attracted extensive attention and research. First,zwitterionicpolymers have an extremely strong hydration ability and can form a dense hydration layer on the material surface. In addition,zwitterionicpolymers exhibit a unique "anti-polyelectrolyte effect", i.e., the addition of small molecules of salt to aqueous solutions increases their viscosity, unlike the "polyelectrolyte effect" exhibited by anionic and cationic polyelectrolytes. To date,zwitterionicpolymers have shown promising applications in various fields such as antifouling coatings, protein modification, drug delivery, and membrane separation materials.

Drug delivery is an important issue in modern medicine, and the selection of suitable drug carriers can effectively enhance drug solubility, prolong in vivo circulation time, enhance drug efficacy, and reduce side effects. A common drug delivery strategy is to usezwitterionicblock copolymers containing amphiphilic units to form micelles with a core-shell structure by self-assembly, and then encapsulate the drug in its hydrophobic core, such as the common anticancer drug adriamycin (DOX). Also, drug delivery systems based onzwitterionicpolymers can be applied to the delivery of nucleic acid drugs. In addition,zwitterionicpolymers can also be used to construct other structural drug delivery systems: Wu and Cheng at the State University of New York at Buffalo have synthesized a biodegradable poly(lactic acid) (PLA) backbone and synthesized PLA-SB/PTX as a coupling between the anticancer drug paclitaxel (PTX) andzwitterionicpolymers, which can release PTX through biodegradation to kill tumor cells. This coupling can release PTX through biodegradation to kill tumor cells and achieve anti-cancer; Shengfu Chen et al. of Zhejiang University prepared anzwitterionicpolymer hydrogel with triple responsiveness of ionic strength, pH and enzyme using polyamino acid as the backbone, which is expected to achieve targeted release of drugs.