Abstract
There is a compelling need for the development of new sensory and neural prosthetic devices which are capable of more precise point stimulation. Current prosthetic devices suffer from the limitation of low spatial resolution due to the non-specific stimulation characteristics of electrical stimulation, i.e., the spread of electric fields generated. We present a visible light stimulation method for modulating the firing patterns of electrically-excitable cells using surface plasmon resonance phenomena. In in-vitro studies using gold (Au) nanoparticle-coated nanoelectrodes, we show that this method (substrate coated with nanoparticles) has the potential for incorporating this new technology into neural stimulation prosthetics, such as cochlear implants for the deaf, with very high spatial resolution. Au nanoparticles (NPs) were coated on micropipettes using aminosilane linkers; and these micropipettes were used for stimulating and inhibiting the action potential firing patterns of SH-SY5Y human neuroblastoma cells and neonatal cardiomyocytes. Our findings pave the way for development of biomedical implants and neural testing devices using nanoelectrodes capable of temporally and spatially precise excitation and inhibition of electrically-excitable cellular activity.
Highlights
Electrical stimulation is used for sensory implants, and, for techniques like electromyography (EMG), a neurological test used to detect and diagnose peripheral neuropathy and related sensorimotor problems, with the annual cost of EMG being approximately 2.8 billion dollars in the US alone[7]
Au NPs synthesized via a liquid phase route were characterized using transmission electron microscopy (TEM) (Fig. 1b) and UV-Vis spectrophotometry
Photocurrents were recorded when an extracellular solution (ECS) having a composition of 140 mM NaCl, 5 mM KCl, 1 mM MgCl2, 2 mM CaCl2, 10 mM HEPES at pH 7.4 maintained with NaOH, was used as the electrolyte instead of phosphate buffer (Fig. 2c) which exhibited a linear relation with applied voltage (Fig. 2e)
Summary
Electrical stimulation is used for sensory implants, and, for techniques like electromyography (EMG), a neurological test used to detect and diagnose peripheral neuropathy and related sensorimotor problems, with the annual cost of EMG being approximately 2.8 billion dollars in the US alone[7]. We stimulated two different cells, SH-SY5Y human neuroblastoma a cell line that has characteristics of neurons, and neonatal cardiomyocytes, with a nanoelectrode and a 532 nm green laser These experiments served as initial, in vitro proof of concept that wireless nanoelectrodes in combination with visible light can be used instead of electrical electrodes or infra-red (IR) lasers, for precise temporal modulation of neural and cardiac cellular responses. Based on these initial breakthrough results, we visualize that future biomedical implants based on LSPR phenomena using nanoelectrodes and light will give superior spatial resolution and more clinically useful focal stimulation. Implantable electrodes such as cochlear implant electrode arrays, which use polymeric materials are designed using the fundamental results demonstrated in this contribution
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