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.

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The pheochromocytoma cell line PC12 displays neuronal characteristics. PC12 cells differentiate their phenotype from a proliferating cell to a neurite-bearing neuron upon treatment with nerve growth factor (NGF). The neurite outgrowth of PC12 cells on polystyrene tissue culture flasks and extracellular matrix protein-adsorbed glass plates was reversibly controlled using visible light. The percentage of cells with neurites decreased with increasing light intensity. Furthermore, neurite outgrowth was dramatically suppressed with light intensities over 300 Lux (approximately 130 microW). Neurite outgrowth occurred in the absence of irradiation by visible light, but did not occur or was limited with irradiation, depending on the membranes on which PC12 cells were cultured. These results hold promise for the creation of patterned neuronal networks corresponding to patterned irradiation of visible light on nerve cells.

A reproducible method to quantify DNA in DNA and protein solutions at ppb levels using flow cytometry analysis is reported herein. After DNA and protein solutions were dyed with fluorescent probe (PicoGreenTM) intercalating, flow cytometric scattergrams of DNA at fluorescent intensities of 525 nm and 575 nm showed a higher intensity of emission at 525 nm than those of proteins. DNA quantitation was performed using calf thymus DNA with two standard curves. The high standard curve showed a semi-logarithmic plot from 1 to 50 ppb with a correlation coefficient of 0.993, whereas the low standard curve described the second-power equation from 0.1 to 5 ppb DNA with a correlation coefficient of 0.998. A flow cytometry analysis of the DNA concentration was powerful for estimating the DNA concentration in a protein solution containing salts, such as saline, because the present flow cytometry analysis showed less than a 37% decline when the DNA solution contained 0.15 mol/L NaCl. The DNA content in albumin, cellulase, γ-globulin, and pepsin was estimated to be 0.078 ± 0.006, 0.26 ± 0.04, 3.0 ± 0.4, and 1.2 ± 0.1 μg-DNA/g-protein (n = 4), respectively, based on flow cytometry analysis of the protein solutions.