Photoresponsive behaviour of zwitterionic polymer particles with photodimerizable groups on their surfaces.

Polymer particles with precise diameters have been used as building blocks for fabricating well-defined and nanostructured materials. Polymer particles as building blocks for medical applications require both easily spatiotemporal manipulation and good biocompatibility. In this study, we designed zwitterionic polymer particles with photodimerizable groups on their surfaces and used ultraviolet (UV) light irradiation to photo-assemble them in aqueous media. After synthesizing zwitterionic polymer particles with diameters ranging from 100-200 nm via soap-free emulsion polymerization, maleimide moieties as photodimerizable groups were introduced onto the particle surfaces. UV light irradiation to an aqueous dispersion of zwitterionic polymer particles with photodimerizable groups induced their photo-assembling because interparticle bonding forms by photodimerization of the photodimerizable groups on the particle surfaces. The zwitterionic surface of their particle-assembled films effectively suppressed protein adsorption, cell adhesion, and platelet adhesion. The photoresponsive behaviour and bioinert surface of the zwitterionic polymer particles with photodimerizable groups indicate that they have several potential applications as bioinert building blocks for designing well-defined and nanostructured biomaterials used in biosensors, bioseparation and cell culture, and for modifying and repairing biomaterial surfaces in situ .