Photo-immobilization of epidermal growth factor enhances its mitogenic effect by artificial juxtacrine signaling

Photo-reactive epidermal growth factor (EGF) was synthesized by coupling EGF with azidobenzoic acid and was immobilized onto the wells of a polystyrene culture plate by photo-irradiation. The photo-immobilized EGF enhanced the growth of anchorage-dependent cells more than native or azidobenzoyl derivatized EGF. A small amount of photo-immobilized EGF was sufficient to enhance the growth of cells and the maximal mitogenic effect was greater than that of native or derivatized EGF. On the other hand, the photo-immobilized EGF did not enhance growth of anchorage-independent cells. In addition, signal transduction in the cells adhered only on the EGF-immobilized surface was observed by staining of phosphotyrosine residues by anti-phosphotyrosine antibodies. These results showed that the enhanced cell growth was due to direct interaction between the cells and the immobilized EGF. Photo-immobilization could be a universal means of fixing growth factors onto an artificial matrix that is devoid of chemically functional groups scaffolding growth factors and could provide a new tool to elucidate signal transduction mechanism and could lead to the development of a new protein-free cell culture system or tissue engineering materials.