Optical recording of neural responses to gold-nanorod mediated photothermal neural inhibition

Abstract

Background: Photothermal stimulation is a heat-mediated neuromodulation technique. When photothermal effects are induced on neuronal membrane, it can either excite or inhibit neural spiking activities. It has been demonstrated that gold nanorod mediated photothermal stimulation could decrease the electrical activity of cultured neural network. We investigated the effect of photothermal inhibition on neural activity using calcium imaging technique.

New method: Hippocampal neurons were cultured on a gold-nanorod-coated-microelectrode array and near-infrared laser was illuminated to induce neural inhibition. The neuronal responses at a single-cell resolution were measured by an extracellular recording and calcium imaging simultaneously.

Results: The photothermal effect on neural spikes were confirmed by electrical recording and calcium imaging. The decrease in neural spikes in electrical recordings during NIR illumination was correlated with the neighboring neural activity quantified by calcium spikes.

Comparison with existing method(s): Optical recording at the single cell resolution was attempted during photothermal stimulation to confirm the neural suppression effect.

Conclusions: Heat mediated suppression of neural activity was optically validated in single cell level. The present study will be helpful to understand the emerging photothermal neuromodulation technology.

Keywords: Calcium imaging; Cell culture; Gold nanorod; Microelectrode array; Neuromodulation; Photothermal effect.