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T. Matsuo, K. Takarabe, T. Uchida; Electric Potential Changes Evoked by Light on the Surface of Photoelectric Dye-Coupled Polyethylene Films (Okayama University-Type Retinal Prostheses). Invest. Ophthalmol. Vis. Sci. 2009;50(13):4220.
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© ARVO (1962-2015); The Authors (2016-present)
We are developing a new type of retinal prostheses using photoelectric dye molecules which absorb light energy and generate electric potentials (Matsuo T, et al as Inventors, US Patent 7,101,533 B2, 2006). Our prototypes, photoelectric dye-coupled polyethylene films, are thin and soft, can be rounded and inserted to the subretinal space through a small retinotomy in standard vitrectomy. A large size of films under the retina would correspond to a large area of the visual field. In general, efficacy, safety, and quality control are three factors for retinal prostheses to be approved as a medical device. We have shown our retinal prostheses to stimulate photoreceptor-lacking retinal tissues and retinal neurons from the standpoint of the efficacy (Artif Organs 2005;29:53-57, 2006;30:695-703). We also revealed no toxicity to neurons and retinal tissues from the standpoint of the safety (J Artif Organs 2008;11:38-44, 11:45-51). In this study, we aim to measure the changes in electric potentials on the surface of our retinal prostheses toward the development of a method for the quality control.
Carboxyl moieties were introduced on the surface of extruded-blown film of high density polyethylene by treatment with fuming nitric acid. A photoelectric dye, 2-[2-[4-(dibutylamino)phenyl]ethenyl]-3-carboxymethylbenzothiazolium bromide (Hayashibara Biochemical Laboratories), was coupled to carboxyl moieties of the film surface through amide linkages by ethylenediamine. Each step of chemical processes was monitored by infrared or visible light absorption spectra. A piece of the film was placed on the stage, and the surface electric potential was scanned and measured by Kelvin Probe (KP Technology Ltd, Wick, UK) under the light and dark conditions.
The two dimensional distribution of electric potentials on the surface of the photoelectric dye-coupled polyethylene films could be measured by the Kelvin Probe. The differences in electric potentials between the condition of room light and the dark condition ranged from 60-100 mV.
The electric potential changes induced by the room light on the surface of the photoelectric dye-coupled polyethylene films are comparable to the range of cell membrane potentials. This study gives further evidence to the efficacy of our retinal prostheses, and the Kelvin Probe method can be used as quality control of our retinal prostheses.
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