Light-Addressed Stimulation Under $\hbox{Ca}^{\bf 2+}$ Imaging of Cultured Neurons

Abstract

Light addressing is an emerging and sophisticated technique that can induce pinpoint and/or patterned neuronal activation in cultured neurons. We previously developed a light-addressable electrode using hydrogenated amorphous silicon (a-Si:H), which was sandwiched between a tin oxide (SnO(2)) substrate and a passivation layer of zinc antimonate (ZnOSb(2)O(5)) dispersed epoxy. This research developed an experimental system that simultaneously implemented light-addressed stimulation and Ca(2+) imaging of neuronal activities. The translucent and thin laminated structure of our electrode permitted optical accesses from two directions: Ca(2+) imaging from above and light addressing from beneath. The submillisecond bright/dark switching property of our electrode offered light-addressed stimulation without causing interference with Ca(2+) imaging. To provide patterned illumination for light addressing, a digital micromirror device was installed in the system as an active photomask. The system could induce pinpoint neuronal activation at a cellular level.

Novel interfaces for light directed neuronal stimulation: advances and challenges

“…For p-type silicon, electrons, which are the minority charge carriers, generate photocurrent upon application of reversed bias. Neuronal stimulation, based on this effect, was demonstrated by several groups utilizing either single crystal, [95][96][97] ( Figure 1A and B) or hydrogenated amorphous silicon (a-Si:H) [98][99][100][101] ( Figure 1C and 1D). …”

“…97,103 However, owing to its poor stability in the physiological solution, it requires a passivation layer. 97 Light addressed recordings of cardiac myocytes, using an array of titanium nitride (TiN) microelectrodes on an a-Si:H photoconductive layer, was reported by Bucher et al 96,104 An a-Si:H layer was sandwiched between indium tin oxide (ITO) leads on a glass substrate, and a layer of microelectrodes embedded in carbonic silicon oxide (SiOx:C) insulation as demonstrated in Figure 1C. The spontaneous activity of cardiac myocytes was recorded upon illumination of the photoconductor with a 488 nm laser beam with a spot diameter of 1.6 µm and intensity of 1.6 mW.…”

“…The spontaneous activity of cardiac myocytes was recorded upon illumination of the photoconductor with a 488 nm laser beam with a spot diameter of 1.6 µm and intensity of 1.6 mW. 96,104 An alternative passivation layer composed of low conductivity zinc antimonite (ZnOSb 2 O 5 ) was suggested by Suzurikawa et al 97,98 An a-Si:H layer was sandwiched between a tin oxide (SnO 2 ) coated glass substrate and a zinc antimonate passivation layer, as demonstrated in Figure 1D. This waterproof, low-conductivity passivation layer prevents spreading currents along the plane.…”

“…Neuronal activation was achieved using 470-495 nm light with intensity of 800 mW/cm 2 , and voltage pulses of 3 V for 1 ms, as verified using calcium imaging. In a subsequent study, the authors further improved the simultaneous light stimulation and the Ca +2 imaging experimental system 97 by incorporation of a digital micro-mirror device to achieve patterned illumination for neuronal activation. Neuronal responses decreased dramatically at approximately 10 µm from the illumination border, suggesting spatial resolution of a single-cell.…”

Digital micromirror based near-infrared illumination system for plasmonic photothermal neuromodulation

“…In contrast, other neuromodulation techniques, which are free of genetic modification, have been developed using photovoltaic and photothermal mechanisms. Photoelectric methods stimulate neurons by generating photocurrents, and it has been reported that photovoltaic materials or photoconductive materials can be used to stimulate retinal ganglion cells [3,4] or cultured neurons [5,6]. Photothermal stimulation is a new method to modulate neural activity by generating heat locally at the periphery of the cell through external light and provide either excitatory or inhibitory stimulus to the cell.…”