The retina has photoreceptor cells which absorb light and convert photon energy to electric potentials on the cell membrane. In this study, in order to develop a prototype of retinal prostheses, a photoelectric dye was immobilized on a polyethylene film surface.

Carboxyl moieties were introduced to polyethylene film surface by reaction with 97% fuming nitric acid at 80C for 20 min in a flask. The fi1m was then washed with water until pH-neutral and dried in air. A photoelectric dye 2-{2-[4-(dibutylamino)phenyl] ethenyl} -3-carboxy methyl- benzothiazolium bromide was then linked to the film through ethylenediamine forming amides in the catalytic presence of dicyclohexylcarbodiimide in chlorobenzene at 35C for 24h.

Intracellular calcium elevation was used as a sign of cell activity response to the dye-immobilized films. Pieces of immature retinal tissues of 12-day-old chick embryos ( loaded with Fluo-4 acetoxymethyl ester; a molecular probe of fluorescence emission) were observed with a fluorescent dissecting microscope in order to monitor intracellular calcium levels in the retinal tissues. Significant elevation of intracellular calcium was observed in the retinal tissues when they were placed on the dye-immobilized films, but without the film, it returned to a low level.　This fact indicated that extracellular calcium ions flew into the retinal cells through voltage-gated calcium channels which the dye-immobilized film triggered on light irradiation.

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