Zwitterionic polymers, comprising hydrophilic anionic and cationic groups with the same total number of positive and negative charges on the same monomer residue, have received increasing attention due to their distinctive physico-chemical properties, including high hydration, good biocompatibility, good antifouling and good antibacterial properties, and thus show great potential as a novel type of biomedical material. Unique topological polymers with block, star, dendritic, comb, brush and cyclic structures not only meet the requirements of material structure accuracy but also provide a theoretical research template for the development of materials science. Topological structures can facilitate polymers with precise and adjustable structures, hydrodynamic size, lower viscosity, more active sites, less intermolecular entanglement, and increased colloidal stability, which can effectively achieve drug encapsulation, improve the drug-loading efficiency, achieve faster internalization, and reduce the in vitro cytotoxicity. Therefore, the synthesis of topological polymers with precise structures has become an inevitable requirement for the development of materials and their biomedical applications. The article mainly reviews the properties and application of zwitterionic polymers and their derivatives with different topological structures. In particular, the recent progress of these polymers in drug delivery, antitumor properties, biomedical diagnosis and antifouling coatings are described and introduced. Finally, the current problems in these applications are discussed, and the potential research prospects of zwitterionic-based topological polymers in current research are put forward.

Enhanced joint synergistic lubrication combined with anti-inflammatory therapy is an effective strategy to delay the progression of early osteoarthritis (OA) but has been rarely reported. The hydration lubrication of zwitterions and inherent super-lubrication properties of the cyclic brush, as well as the enhancement of the steric stability of the cyclic topology, can effectively improve the drug loading and utilization; herein we report a pH-responsive cyclic brush zwitterionic polymer (CB) with SBMA and DMAEMA as brushes and a cyclic polymer (c-P(HEMA)) as the core template, possessing a low coefficient of friction (0.017). After loading with hydrophobic curcumin and hydrophilic loxoprofen sodium it demonstrates high drug-loading efficiency. In vitro and in vivo experiments confirmed the triple function of the CB on superlubrication, sequence controlled release and anti-inflammatory effects demonstrated by Micro CT, histological analysis and qRT-PCR. Overall, the CB is a promising long-acting lubricating therapeutic agent, with potential for OA treatment or other diseases.