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Amel Bendali, Elisabeth Dubus, Julie Dégardin, Gaelle Lissorgues-Bazin, Lionel Rousseau, Milan Djilas, Philippe Bergonzo, Ryad Benosman, Serge Picaud, José-Alain Sahel; Retinal Prostheses: Diamond Biocompatibility And 3D Structure. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5528.
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In AMD and inherited dystrophies like RP, partial preservation of the inner retina has been demonstrated. This finding has led to developing various models of retinal implants to restore vision. As diamond exhibits good biocompatibility and an interesting potential window, we investigated its possible use on retinal implants. Diamond biocompatibility for retinal cells was investigated first with cultures and then in vivo using the P23H rat, a model of RP. We also investigated how the tissue reacts to 3D-shaped implants increasing the spatial resolution of stimulating electrodes.
Diamond samples and diamond coated soft electrodes were produced at CEA (Saclay) and ESIEE (Noisy le Grand). Retinal cell cultures from adult rats were seeded on diamond. Soft implants with diamond and metallic electrodes were introduced in the subretinal space of P23H rats for 8 weeks, to assess the glial reaction. In parallel, 3D-shaped polyimide implants were also tested in vivo. The implants were examined in vivo by OCT in implanted P23H rats prior to the histological study (bipolar cells and glia stained).
Pure RGC cultures showed that retinal neurons can survive on diamond independently of glial cells. As on glass, the high survival rate and the long neuritic outgrowth on diamond demonstrated its good biocompatibility for retinal neurons, even without a protein coating. Our soft polyimide implants were successfully inserted into the subretinal space of P23H rats. Metal and diamond coatings were compared, as well as 3D-shaped versus flat electrodes. OCT images showed a nice integration of the tissue within the 3D structures of the implant. Immunostaining of both bipolar and glial cells indicated that the degenerated retina was able to mould into the 3D-structures where numerous bipolar cells were observed.
Our cell cultures showed a comparable survival and neuritic outgrowth of adult retinal neurons on diamond or glass independently of any coating. The diamond coating allowed a good integration of soft polyimide implants within the subretinal space of P23H rats. 3D-shaped implants allowed a nice integration of the degenerated tissue so that local stimulation is likely to occur. Therefore, this study supports that diamond-coated and 3D-shaped implants could provide biocompatible neuroprostheses for very focal neuronal stimulations.
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