On-off affinity binding modulation on thermoresponsive polymer-grafted surfaces for capture and release of proteins and cells.

This review describes new types of thermoresponsive surfaces modified with biologically active ligands to thermally modulate on-off affinity binding between ligands and receptors. To achieve the thermal regulation of affinity binding, molecules of thermoresponsive polymer poly(N-isopropylacrylamide) (PIPAAm) are typically used to tune the degree of steric hindrance in response to temperature. The coil-to-globule transition of surface-grafted PIPAAm chains induces dynamic changes in the degree of steric hindrance in the vicinity of the immobilized ligand, resulting in the thermoresponsive modulation of on-off affinity interactions with receptors, and the subsequent on-off switching of the capture and release of proteins and cells on the surface. Thermoresponsive biomaterial surfaces to modulate on-off affinity binding between ligands and receptors has potential to realize the creation of functional cell sheet-based tissues, as well as novel separation system of specific proteins and cells without any labeling. These materials will thus be beneficial for clinical use in cell-based therapies, including tissue engineering and regenerative medicine.