Micropatterned immobilization of epidermal growth factor to regulate cell function

Photoreactive epidermal growth factor (EGF) was synthesized by conjugating mouse EGF with photoreactive polyallylamine, which was synthesized by the coupling reaction of polyallylamine with N-[4-(azidobenzoyl)oxy]succinimide. The EGF derivative was pattern-immobilized onto a polystyrene plate by UV irradiation in the presence of a photomask in a prescribed micropattern. The patterned immobilization of EGF on the polystyrene plate was confirmed by immunostaining with anti-EGF antibody. Chinese hamster ovary (CHO) cells overexpressing EGF receptors were cultured on the micropatterned plate. The phosphorylated tyrosine residues of signal proteins, including EGF receptors, were detected only in the cells adhered in the EGF-immobilized area, and cell growth was observed only in the EGF-immobilized area. The cells growing in the EGF-immobilized area were partially stained by anti-phosphotyrosine antibody, when the area of EGF immobilization was smaller than the cell. The partial staining of activated proteins indicates that immobilization of EGF inhibited the free lateral diffusion and internalization of the activated EGF-EGF receptor complex. The enhanced cell growth is due to juxtacrine stimulation realized by immobilized EGF.