Closed-loop control of neural spike rate of cultured neurons using a thermoplasmonics-based photothermal neural stimulation

Abstract

Objective. Photothermal neural stimulation has been developed in a variety of interfaces as an alternative technology that can perturb neural activity. The demonstrations of these techniques have heavily relied on open-loop stimulation or complete suppression of neural activity. To extend the controllability of photothermal neural stimulation, combining it with a closed-loop system is required. In this work, we investigated whether photothermal suppression mechanism can be used in a closed-loop system to reliably modulate neural spike rate to non-zero setpoints. Approach. To incorporate the photothermal inhibition mechanism into the neural feedback system, we combined a thermoplasmonic stimulation platform based on gold nanorods (GNRs) and near-infrared illuminations (808 nm, spot size: 2 mm or 200 μm in diameter) with a proportional-integral (PI) controller. The closed-loop feedback control system was implemented to track predetermined target spike rates of hippocampal neuronal networks cultured on GNR-coated microelectrode arrays. Main results. The closed-loop system for neural spike rate control was successfully implemented using a PI controller and the thermoplasmonic neural suppression platform. Compared to the open-loop control, the target-channel spike rates were precisely modulated to remain constant or change in a sinusoidal form in the range below baseline spike rates. The spike rate response behaviors were affected by the choice of the controller gain. We also demonstrated that the functional connectivity of a synchronized bursting network could be altered by controlling the spike rate of one of the participating channels. Significance. The thermoplasmonic feedback controller proved that it can precisely modulate neural spike rate of neural activity in vitro. This technology can be used for studying neuronal network dynamics and might provide insights in developing new neuromodulation techniques in clinical applications.

NiSe and CoSe Topological Nodal‐Line Semimetals: A Sustainable Platform for Efficient Thermoplasmonics and Solar‐Driven Photothermal Membrane Distillation

“…[ 1 ] Upon illumination at the plasmon frequency, metal NPs display enhanced light absorption, enabling efficient light‐to‐heat conversion. [ 1a ] Recently, thermoplasmonic effects have been successfully exploited mainly for biomedical applications, such as photothermal cancer therapy, [ 2 ] neural stimulation, [ 3 ] bacteria killing, [ 4 ] intracellular delivery of miRNA, [ 5 ] photothermal biosensors for SARS‐CoV‐2 detection. [ 6 ] Additionally, thermoplasmonic effects also play a pivotal role in photothermal actuators, [ 7 ] nanofurnaces for heterogeneous catalysis, [ 8 ] and solar‐driven water evaporation.…”

Enhancement of Thermoplasmonic Neural Modulation Using a Gold Nanorod-Immobilized Polydopamine Film

“…Recently, the finetuning of neural activity control using the closed-loop system was shown, which was equipped with a proportional-integral (PI) controller. 27 With our enhanced photothermal effects with the use of the pDA and GNRs combination, we believe that we may control the neural activity in more energy-efficient conditions.…”

“…Moreover, the substrate with GNRs immobilized on the pDA film not only allows a total inhibition of neural activity with the least laser power but also the reduced spike rate when stimulated with the less laser power density required for full inhibition. Recently, the fine-tuning of neural activity control using the closed-loop system was shown, which was equipped with a proportional-integral (PI) controller . With our enhanced photothermal effects with the use of the pDA and GNRs combination, we believe that we may control the neural activity in more energy-efficient conditions.…”

“…To compare the result with the photothermal inhibition experiment, the same temperature change was induced by adjusting the laser power with the different illumination areas. To do so, we used the photothermal conversion equation from our previous work to adjust the laser power . Briefly, the temperature change at the illuminated surface was expressed as the product of beam diameter and laser power density, and the target laser power density was calculated.…”

“…To do so, we used the photothermal conversion equation from our previous work to adjust the laser power. 27 Briefly, the temperature change at the illuminated surface was expressed as the product of beam diameter and laser power density, and the target laser power density was calculated. Laser power densities used for two different beam diameters are shown in the Supporting Information (Table S1).…”