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Near-infrared deep brain stimulation via upconversion nanoparticle–mediated optogenetics

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Science  09 Feb 2018:
Vol. 359, Issue 6376, pp. 679-684
DOI: 10.1126/science.aaq1144
  • Fig. 1 UCNP-mediated NIR upconversion optogenetics for deep brain stimulation.

    (A) Schematic principle of UCNP-mediated NIR upconversion optogenetics. (B) Transmission electron microscopy (TEM) images of the silica-coated UCNPs. (Inset) High-resolution TEM image showing the core-shell structure. (C) Schematic design of a blue-emitting NaYF4:Yb/Tm@SiO2 particle. (D) Emission spectrum of the NaYF4:Yb/Tm@SiO2 particles under excitation at 980 nm. (Inset) Upconversion emission intensity of UCNPs [0.18 mg, 200 mg/ml in 900 nl of phosphate-buffered saline (PBS)] as a function of excitation intensity at 980 nm. (E) Size distribution of the UCNPs measured by dynamic light scattering. No aggregation is observed in water, PBS, or bovine serum albumin (BSA, 1 mg/ml in PBS) solution. (F) Scheme of in vivo fiber photometry for measuring UCNP-mediated NIR upconversion in deep brain tissue. The tip of an optic fiber transmitting NIR excitation light was positioned at various distances from the VTA where UCNPs were injected, and their emission was recorded by a second optic fiber. (G) Upconversion emission at the VTA upon 980-nm NIR irradiation (25-ms pulses at 20 Hz, 2.0-W peak power) from varying distances. (H) Measured (n = 4 mice) and simulated intensity of upconversion emission at the VTA as a function of the distance from the NIR irradiation source. Data are presented as mean ± SEM.

  • Fig. 2 NIR excitation of VTA DA neurons in vitro.

    (A) Experimental scheme. AAV-DIO-ChR2-EYFP was injected into the VTA of TH-Cre transgenic mice for Cre-dependent expression of ChR2 in DA neurons. Four weeks later, 900 nl of 200 mg/ml blue-emitting NaYF4:Yb/Tm@SiO2 UCNPs was injected into the VTA. Horizontal acute slices containing the VTA were prepared, and in vitro whole-cell recordings were performed. (B) Electron micrographs of UCNPs distributed in the VTA tissue. Black arrows indicate clusters of UCNPs. The upper image shows the distribution of the majority of UCNPs in extracellular space, and the lower image shows the uptake of UCNPs by an axon. (C) Voltage-clamp traces of neurons from VTA slice preparations in response to 100-ms NIR stimulation at various intensities. NIR light triggered photocurrents only in ChR2-transfected neurons in the presence of UCNPs. The traces for ChR2(−) and UCNP(−) controls in black were recorded under 8.22-W/mm2 NIR irradiation. (D) Increase in photocurrent amplitude with elevated intensity of the NIR stimulation (n = 6 cells). (E) Current-clamp traces of a ChR2-expressing DA neuron in response to trains of 10 NIR pulses at different frequencies (20-ms pulses at 10 and 20 Hz, 10-ms pulses at 50 Hz, 8.22-W/mm2 peak power) in the presence of UCNPs. Brief red lines indicate NIR pulses. (F) Spike probability as a function of the frequency of NIR stimulation (n = 6 cells). Data are presented as mean ± SEM.

  • Fig. 3 Transcranial NIR stimulation of VTA DA neurons in vivo.

    (A) In vivo experimental scheme for transcranial NIR stimulation of the VTA in anesthetized mice. (B) Confocal images of the VTA after transcranial NIR stimulation under different conditions. Extensive NIR-driven c-Fos (red) expression was observed only in the presence of both UCNPs (blue) and ChR2 expression (labeled with EYFP, green). Scale bars: 100 μm. (C) Percentage of c-Fos–positive neurons within cell population indicated by DAPI (4′,6-diamidino-2-phenylindole), corresponding to the four conditions presented in (B) (n = 3 mice each, F3,8 = 10.40, P < 0.01). (D) Scheme of in vivo FSCV to measure DA transients in ventral striatum during NIR stimulation of the VTA. (E) Relative DA signals in ventral striatum under NIR and blue-light stimulation of the VTA as a function of the distance from the light source to the VTA target. (F) A trace of background-subtracted current measured by FSCV in the ventral striatum of a nomifensine-pretreated mouse in response to transcranial NIR stimulation of the VTA (15-ms pulses at 20 Hz, 700-mW peak power). Vertical dashed lines marked by a horizontal orange line in between indicate the start and end of 2-s transcranial NIR stimulation. (G and H) Transient DA concentrations in ventral striatum in response to transcranial VTA stimulation under different conditions. Each color corresponds to a condition shown in (I). Significant DA release temporally locked to NIR stimulation was detected only in the presence of both UCNPs and ChR2 expression. (I) Cumulative DA release within 15 s after the start of transcranial stimulation under the five conditions presented in (G) and (H) (F4,10 = 32.93, P < 0.0001). Data are presented as mean ± SEM.

  • Fig. 4 Expanding in vivo upconversion optogenetics to multiple neural systems.

    (A) Schematic of a green-emitting NaYF4:Yb/Er@SiO2 particle. (B) Illustration of transcranial NIR inhibition of hippocampal (HIP) activity during chemically induced seizure. (C) Confocal images of the hippocampus following transcranial NIR stimulation under different conditions. Significant decrease in c-Fos (red) expression was observed only in the presence of both UCNPs (green) and Arch expression (labeled with EYFP, blue). Scale bars: 400 μm. (D) c-Fos expression under the four conditions presented in (C) (n = 3 mice each, F3,8 = 94.02, P < 0.0001). (E) Illustration of transcranial NIR stimulation of medial septum (MS) for generation of theta oscillations. (F) Confocal images showing the overlap between ChR2-expressing PV interneurons (labeled by EYFP, green) and UCNPs (blue) in the MS of a PV-Cre mouse. Scale bars: 50 μm. (G) Hippocampal LFP in response to 8-Hz transcranial NIR stimulation (15-ms pulses, 10 s, 3.0-W peak power, 360-mW average power) of MS under different conditions. Top: Raw LFP trace from mouse with both UCNP and ChR2 injection. Bottom: Z-scored power in the theta range averaged across 30-s trials in all three conditions. (H) Transcranial NIR entrainment of hippocampal theta in a frequency-dependent manner. (I) Illustration of transcranial NIR stimulation of hippocampal engram for memory recall. (J) Confocal image showing the overlap between UCNPs (blue) and ChR2 expression (labeled with EYFP, green) in the DG of a mouse that underwent habituation, fear conditioning, and test sessions presented in (K). Scale bar: 200 μm. (K) Mice were on Dox food and habituated with NIR stimulation (15-ms pulses at 20 Hz, 250-mW peak power) in context A for 5 days, then off Dox food for 2 days and fear conditioned in context B. Mice were put back on Dox food and tested for 5 days in context A with transcranial NIR stimulation. (L to N) After fear conditioning, only c-fos-tTA mice with both ChR2 expression and UCNP injection showed increased freezing during 3-min NIR-on periods. Orange lines indicate the NIR-on epochs. (O) Summary of freezing levels of the three groups during test NIR-on epochs (F2,26 = 105.9, P < 0.0001). Data are presented as mean ± SEM.

Supplementary Materials

  • Near-infrared deep brain stimulation via upconversion nanoparticle–mediated optogenetics

    Shuo Chen, Adam Z. Weitemier, Xiao Zeng, Linmeng He, Xiyu Wang, Yanqiu Tao, Arthur J. Y. Huang, Yuki Hashimotodani, Masanobu Kano, Hirohide Iwasaki, Laxmi Kumar Parajuli, Shigeo Okabe, Daniel B. Loong Teh, Angelo H. All, Iku Tsutsui-Kimura, Kenji F. Tanaka, Xiaogang Liu, Thomas. J. McHugh

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Supplementary Text
    • Figs. S1 to S18
    • Tables S1 and S2
    • References

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