Abstract
Conventional microelectrode arrays (MEAs) cannot always access desired neurons due to low electrode density and small electrode number. To overcome this problem, we have proposed and developed a light-addressable planar electrode on a glass substrate. The electrode has a 3-layer structure, namely a transparent SnO2 layer, an hydrogenated amorphous silicon (a-Si:H) layer, and a low-conductive passivation layer. Illumination to the a-Si:H layer increases the conductivity of a-Si:H and generates a virtual electrode at the surface of the illuminated site. In the present study, we evaluated the photoelectric property of the developed electrode and estimated the spatial resolution of the light-addressed stimulation. Illumination to the electrode increased stimulus intensity by up to 60-folds. This illumination-induced intensity change sufficiently followed high-frequency illumination switching. The simultaneous fluo-4 Ca2+-imaging, thus, successfully monitored post-stimulus fluorescence transients by instantaneously shutting out the excitation light during stimulus pulse application. By monitoring stimulus induced responses of cell aggregations, we estimated the spatial resolution of the light-addressed stimulation at 10 μm or more with an addressing illumination spot of 70 μm in diameter.
