Effect of protein and cell behavior on pattern-grafted thermoresponsive polymer.

A thermoresponsive copolymer, poly(Nisopropylacrylamide-co-acrylic acid), was coupled with azidoaniline. The azidophenyl-derivatized copolymer was grafted in a specific pattern on a polystyrene matrix by photolithography. The surface micropattern appeared and disappeared interchangeably, as observed under a phase-contrast microscope, by varying the temperature between 10 degrees C and 37 degrees C. The copolymer-grafted polystyrene surface was hydrophobic at 37 degrees C and hydrophilic at 10 degrees C. Albumin and fibronectin adsorption on the matrix was investigated using the fluorescent-labeling method. Fibronectin adsorbed onto both the grafted and nongrafted regions, while albumin adsorbed more onto the nongrafted regions than the grafted regions. Protein adsorption did not affect surface wettability. Mouse fibroblast STO cells were cultured on tissue culture plates pattern-grafted with the thermoresponsive copolymer. Fibronectin adsorption enhanced cell spreading, while albumin reduced it. When the temperature was lowered, the cells selectively detached from the surface areas grafted with the thermoresponsive copolymer when cultured in serum-free medium; the cells partially detached from these areas when cultured in serum-containing medium. The effect of serum proteins on cell detachment was similar to that caused by a mixture of albumin and fibronectin. Albumin adsorption did not affect the detachment of cells, while fibronectin adsorption inhibited it. The results of the present study indicate that a pattern-grafted, thermoresponsive, azidophenyl-derivatized copolymer can effectively facilitate selective cell detachment under some conditions such as serum-free culture or preadsorption of albumin. The pattern-grafting technique will be useful for qualitative microscopic comparison of surfaces prepared differently on one chip under the same conditions.