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Gradient micropattern immobilization of a thermo-responsive polymer to investigate its effect on cell behavior.

A gradient micropattern immobilization technique using a photomask was developed to investigate by microscopic observation the effect of the surface concentration of an immobilized thermo-responsive polymer. Poly(N-isopropylacrylamide-co-acrylic acid) was chosen as the thermo-responsive polymer, and was conjugated with 4-azidoaniline to form a photo-reactive thermo-responsive polymer (PIA-Az). The PIA-Az was coated onto a polystyrene plate, and immobilized using UV irradiation in the presence of a gradient micropattern photomask. The immobilization was performed with and without gelatin. Mouse fibroblast STO cells cultured on the plate did not adhere to the surface when PIA-Az had a high surface density, and no cell detachment was observed in any region when the temperature was lowered. However, on the gelatin coimmobilized surfaces, the cells adhered to all surfaces independent of the PIA-Az density, and detached from the high PIA-Az surface density areas when the temperature was lowered. The present technique demonstrates the effect of the surface concentration-dependent immobilization of the molecules. We show that cell detachment can be regulated by perturbating a small part of the cell-immobilized polymer interface.