Fig. 6: Examples of plasmonic/thermoplasmonic nanotools.

a Numerical investigation of the effects of photothermal stimulation on brain modulation by a thermoplasmonic optical fiber (Reprint permitted under Term of Use from ref. ¹¹⁵). b Illustration of a thermoplasmonic fiber tip for NIR in vitro localized photothermal neural stimulation on microelectrode array (MEA) chips. Direct inhibition of the network of neurons occurred as a result of localized heat generated by the gold nanorod (GNR)-coated fiber tip. Neurons far from the fiber tip remained unaffected. c Extinction spectrum and infrared thermographic image of the fiber delivering NIR light. The white arrow in the inset shows the localized temperature change at the tip (Reprinted with permission from ref. ¹¹⁷). d A schematic of the SPR system for neuromodulation and detection of the reflection intensity of the laser beam through a multichannel photodetector array (Reprinted with permission from ref. ⁴¹). e Distributed gold nanorods (GNRs) in the vicinity of the plasma membrane of nerve tissues absorb light energy at 980 nm. Pulsed infrared illumination photothermally heats GNRs, increasing the local temperature at the membrane and inhibiting neural activity. TEM image of a cross-sectional view of rat sciatic nerve after injecting GNRs. Compound nerve action potentials recorded from a rat sciatic nerve in vivo with and without gold nanorods, upon exposure energy of 0.641 J. cm⁻² (Reprinted with permission from ref. ¹²⁰). f Schematics of the inkjet-printed thermoplasmonic interface for patterned neuromodulation (Reprinted with permission from ref. ¹²²). g Schematic showing the enhancement of the fluorescence spectra of voltage-sensitive dye on a layer-by-layer (LbL) substrate when neurons are on a GNR-coated nanoplasmonic substrate. The corresponding peak values of fluorescence of voltage-sensitive dye with respect to the different numbers of LbL are plotted (Reprinted with permission from ref. ¹²⁴). h Simultaneous microelectrode recording and calcium imaging from cultured neurons with NIR light-sensitive GNRs during photothermal illumination (Reprinted with permission from ref. ¹⁰⁰). i Scanning electron microscopy images (SEM) images of Au nanowire (AuNW) electrodes obtained with anodic aluminum oxide templates. (A) Top, and (B) cross-section view of an ordered network of parallel AuNWs of 1.2 μm in length and 160 nm in diameter standing over a flexible Au base. (C) SEM images from primary neural cell cultures at high cell seeding conditions. SEM images from cultures at low cell seeding conditions on top (D) and 45^∘ tilted (E) views. Scale bars: 2 μm (A), 0.5 μm (A-inset), 5 μm (B) and 1 μm (B-inset), 200 μm (C, left), 100 μm (C, middle), 10 μm (C, right), 4 μm (D and E, left) and 400 nm (D and E, right) (Reprinted with permission from ref. ¹³³).