Abstract
Light-mediated neuromodulation techniques provide great advantages to investigate neuroscience due to its high spatial and temporal resolution. To generate a spatial pattern of neural activity, it is necessary to develop a system for patterned-light illumination to a specific area. Digital micromirror device (DMD) based patterned illumination system have been used for neuromodulation due to its simple configuration and design flexibility. In this paper, we developed a patterned near-infrared (NIR) illumination system for region specific photothermal manipulation of neural activity using NIR-sensitive plasmonic gold nanorods (GNRs). The proposed system had high power transmission efficiency for delivering power density up to 19 W/mm2. We used a GNR-coated microelectrode array (MEA) to perform biological experiments using E18 rat hippocampal neurons and showed that it was possible to inhibit neural spiking activity of specific area in neural circuits with the patterned NIR illumination. This patterned NIR illumination system can serve as a promising neuromodulation tool to investigate neuroscience in a wide range of physiological and clinical applications.
Highlights
Light-mediated neuromodulation techniques provide great advantages to investigate neural circuits due to its high spatial and temporal resolution
The power of light reflected from each small square Digital micromirror device (DMD) area in Fig. 2(a), was measured for every component (9 × 16) and displayed as a contour plot in Fig. 2(a)
For the first time, we developed DMD-based patterned NIR illumination and successfully demonstrated localized inhibition of neural activity using a gold nanorods (GNRs)-coated microelectrode array (MEA) under patterned NIR illumination
Summary
Light-mediated neuromodulation techniques provide great advantages to investigate neural circuits due to its high spatial and temporal resolution. Optogenetic technique modulates membrane potential by genetically modified light-sensitive ion channels. Its highly specified cell targeting ability, ion channel specificity and wavelength specificity open up various neuromodulation approaches from neurophysiology study to clinical trials [1,2]. Other neuromodulation techniques, which are free of genetic modification, have been developed using photovoltaic and photothermal mechanisms. 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. Irradiating infrared light, which generates heats to the surrounding medium for neurons, has been developed to excite [7] as well as inhibit [8] neural activity. Other small photo-absorbing materials such as microbeads or conjugate polymer were demonstrated to modulate neural activity [11,12]
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