Visible-light-triggered recovery of biologically intact cells using smart fluoropolymer-nanocoated materials

Smart biointerfaces have attracted significant interest for regulating interactions with cells and biomacromolecules. Although stimuli-responsive changes in hydrophobicity are promising for this purpose, the effects of hydrophobic enhancement on cell adhesion behavior remain poorly understood. This study investigated a unique cell recovery system involving a visible (Vis)-light-induced change in the hydrophobicity of a smart surface from moderate to strong. To construct smart surfaces, photoresponsive spirobenzopyran-pendant fluoroalkyl polymers were spin-coated on glass coverslips. The surface properties were characterized after irradiation with ultraviolet (UV; 352 nm) or Vis (530 nm) light. Upon alternating exposure to UV and Vis light, the water wettabilities of the 1.0 w/v% polymer-coated surfaces changed (contact angles of 78° and 88°, respectively) owing to photoisomerization between the polar merocyanine and nonpolar spiropyran forms of the installed spirobenzopyrans, consistent with the observed optical properties. Atomic force microscopy showed that the polymer-coated surfaces were nanoscale flat forms without any phase-separated structures, regardless of photoswitching. After UV irradiation, bovine carotid artery endothelial cells adhered and proliferated on the moderately hydrophobic merocyanine-containing fluoropolymer surfaces. However, subsequent Vis irradiation induced spontaneous cell detachment, possibly because of the increase in surface hydrophobicity. Moreover, Vis irradiation of confluent cultured cells produced biologically intact cell sheets that retained a cell-adhesive fibronectin matrix and cell-cell junctions. This noncytotoxic Vis-triggered cell recovery system can contribute to the development of tissue engineering and cell transplantation therapies.