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Spiropyran is a photoresponsive molecule, and nonionic spiropyran is reversibly changed by UV irradiation to a hydrophilic polar, zwitterionic merocyanine isomer, and back again by visible light irradiation. A copolymer of nitrobenzospiropyran and methyl methacrylate, poly(NSP-co-MMA) was used as a material with a photosensitive surface. UV irradiation of the photosensitive surface of poly(NSP-co-MMA)-coated glass plates decreased the water contact angles (11 +/- 1 degrees ) and increased diameter of a water drop relative to the unexposed surface. Light-induced detachment of platelets and mesenchymal stem (KUSA-A1) cells on poly(NSP-co-MMA)-coated glass plates was observed upon simple- and patterned-light irradiation, whereas no light-induced detachment of platelets and mesenchymal stem cells was observed on poly(methyl methacrylate)-coated glass plates. This is a result of the change from a closed nonpolar spiropyran to the polar zwitterionic merocyanine isomer induced by UV irradiation. Light-induced detachment of fibrinogen adsorbed on poly(NSP-co-MMA) coated glass plates was also observed in this investigation.

Cell separation from peripheral blood was investigated using surface-modified polyurethane (PU) membranes with different functional groups. Both red blood cells and platelets could pass through unmodified PU and PU-SO 3 H membranes, whereas the red blood cells preferentially passed through PU-N(C 2 H 5 ) 2 and PU-NHC 2 H 4 OH membranes. The permeation ratio of T and B cells was Ͻ25% for the surface-modified and unmodified PU membranes. CD34 ϩ cells have been recognized as various kinds of stem cells including hematopoietic and mesenchymal stem cells. The adhesiveness of CD34 ϩ cells on the PU membranes was found to be higher than that of red blood cells, platelets, T cells, or B cells. Overall, the adhesiveness of blood cells on the PU membranes increased in the following order: red blood cells Յ platelets Ͻ T cells Յ B cells Ͻ CD34 ϩ cells. Treatment of PU-COOH membranes with a human albumin solution to detach adhered blood cells, allowed recovery of mainly CD34 ϩ cells in the permeate, whereas both red blood cells and platelets could be isolated in the permeate using unmodified PU membranes. The PU membranes showed different permeation and recovery ratios of specific cells depending on the functional groups attached to the membranes.

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