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T. Matsuo, K. Okamoto, T. Tamaki, O. Hosoya, K. M. Tsutsui, T. Uchida; Safety of Photoelectric Dye and Dye-Coupled Polyethylene Films as Prototypes of Okayama University-Type Retinal Prostheses. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1787.
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© ARVO (1962-2015); The Authors (2016-present)
We designed a new type of retinal prostheses: polyethylene films coupled with photoelectric dyes which absorb light and convert photon energy to electric potentials (US Patent, Artificial Organs 2005;29:53-57 & 2006;30:695-703). In this study, we tested the safety of the photoelectric dye in cell culture, and we implanted the prototypes in rat eyes.
The 12-day chick embryonic retinal cells were cultured for 2 days under dark or 9-hours-daily light exposure with a photoelectric dye, 2-[2-[4-(dibutylamino)phenyl]ethenyl]-3-carboxymethylbenzothiazolium bromide, and cells were stained for dead and live cells. The retinal pigment epithelial cells were incubated with the dye for 4 hours and cell membrane permeability was tested by lactate dehydrogenase leakage. The two prototypes, original dye-coupled polyethylene film and dye-coupled recrystallized film, as well as the plain polyethylene film as a control, were implanted into subretinal space of Wistar rat eyes and examined histologically one week and one month after the implantation.
Retinal cells were predominantly neurons, wtih a small number of glial cells. The retinal cells grew significanlty better at dark (P=0.02, two factor ANOVA) whereas the dye presence did not influence cell growth (P=0.18). Only a few retinal cells were dead: the dead cell percentage was significantly smaller with a higher dye concentration (P=0.01, two factor ANOVA) while the percentage did not differ between the dark and light condition (P=0.31). Percent cytotoxicity of retinal pigment epithelial cells was significantly smaller at dark (P=0.02, two factor ANOVA) but did not differ with dye concentrations(P=0.08). In rat eyes with the prototypes, tissue damage was negligible with few apoptotic cells and no inflammatory cells. GFAP was significantly up-regulated at the site of film implantation, compared with the adjacent right and left sites at one week and at one month (P<0.05, one factor ANOVA). Glial encirclement of the films increased significantly from one week to one month (P=0.02, two factor ANOVA) but did not differ among three films (P=0.45). The glial encirclement did not exceed 50% of the film circumference at one month.
The photoelectric dye showed no cytotoxicity or rather had cytoprotective effects, and the prototypes induced no marked tissue reaction.
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