Figure 2. Nanomaterial Based Photothermal Stimulation of Neurons.
(a) Schematic diagram of a gold nanoparticle locally heating the cell membrane, changing the membrane’s capacitance, Cm, and inducing a depolarization event. (b) Equivalent circuit diagram, showing the net surface potential (Vs), capacitive current (Ic), membrane resistance (Rm), reversal potential (Vr) and ionic current (Ii) respectively. (c) Predicted time derivatives of capacitive current for varying laser pulse powers (high to low power, from top to bottom), indicating that Ic is maximized with higher intensity lasers at the time of pulse initiation (d) Corresponding experimentally measured photothermally induced neuronal action potential (25 × 95 gold nanorod, 785 nm, 5 mW, 1 ms laser pulse). (e) Transmission Electron Microscope (TEM) micrograph of hexagonally packed silicon nanowires, with the mesoporous structure enabling rapid localized heating (scale bar 100nm). (f) Membrane potential recordings of DRG neurons photothermally stimulated using mesoporous silicon, at different frequencies (Left, 5.32 µJ), with corresponding normalized Fast-Fourier Transforms (right). Green ticks indicate the time of delivery for the laser pulse. F and F0 are the output and input frequencies receptively. Modified and reproduced with permission from J. Carvalho-de-Souza et al.61 (b-d) and Y. Jiang et al.61 . (e-f). Copyright 2017 Elsevier and 2016 Springer Nature respectively.