A thermoresponsive poly(N-vinylcaprolactam-co-sulfobetaine methacrylate) zwitterionic hydrogel exhibiting switchable anti-biofouling and cytocompatibility

Non-specific protein adsorption adversely affects the application of thermoresponsive polymers in the biomedical field. To overcome this disadvantage, thermoresponsive N-vinylcaprolactam (VCL) and anti-biofouling zwitterionic sulfobetaine methacrylate (SBMA) monomers with various VCL/SBMA ratios were used for the synthesis of poly(VCL-co-SBMA) (P(VCL-co-SBMA)) copolymers via free radical solution polymerization. The P(VCL-co-SBMA) copolymers exhibited both a lower critical solution temperature (LCST) and an upper critical solution temperature (UCST) in aqueous solutions. Furthermore, both the UCST and LCST of the copolymer shift to higher temperatures with the increase of PSBMA segments, and they shift to lower temperatures with the increase of salt concentrations in the solution. Based on these results, P(VCL-co-SBMA) hydrogels were prepared using N,N'-methylenebisacrylamide (MBAA) as the crosslinker. Compared with the PVCL hydrogel, the P(VCL-co-SBMA) hydrogels exhibit better mechanical properties. Notably, the P(VCL-co-SBMA) hydrogel retained the temperature sensitivity of PVCL, and it could be modulated by varying the PVCL/PSBMA segment ratios. In addition, all the hydrogels exhibit good cytocompatibility. More importantly, the protein adsorption and cell adhesion of the hydrogel can be controlled by temperature. The non-specific protein adsorption was effectively suppressed at physiological temperatures. The switchable anti-biofouling nature of P(VCL-co-SBMA) hydrogel together with their temperature sensitivity can be potentially used in drug, cell or enzyme delivery.