advances.sciencemag.org/cgi/content/full/3/3/e1600955/dc1 Supplementary Materials for Flexible and stretchable nanowire-coated fibers for optoelectronic probing of spinal cord circuits Chi Lu, Seongjun Park, Thomas J. Richner, Alexander Derry, Imogen Brown, Chong Hou, Siyuan Rao, Jeewoo Kang, Chet T. Moritz, Yoel Fink, Polina Anikeeva The PDF file includes: Published 29 March 2017, Sci. Adv. 3, e1600955 (2017) DOI: 10.1126/sciadv.1600955 fig. S1. Controlled parameters during the drawing of the PC/COC fiber. fig. S2. Optical transmission spectra of PC/COC fibers at visible wavelengths. fig. S3. Transmission at a wavelength λ = 473 nm for COCE fiber. fig. S4. Impedance of COCE fibers coated with a single layer of AgNW mesh and measured at 0, 10, and 20% extension strain. fig. S5. Spontaneous single units isolated during acute anesthetized recordings (see Fig. 5, C to F). fig. S6. Electrophysiological recording collected from the freely moving mice implanted with fiber probes. fig. S7. Additional in vivo sensory and electromyographic recordings. fig. S8. Electrophysiological recordings of optically stimulated activity. fig. S9. In vivo EMG recordings. fig. S10. Immunohistochemical analysis of the dorsal horn 2 weeks after device implantation surgeries. Legend for video S1 Other Supplementary Material for this manuscript includes the following: (available at advances.sciencemag.org/cgi/content/full/3/3/e1600955/dc1) video S1 (.mp4 format). Optical spinal control of muscle activity.
fig. S1. Controlled parameters during the drawing of the PC/COC fiber. (A) Stress applied to the fiber with a polycarbonate (PC) core and cyclic olefin copolymer (COC) cladding during the thermal drawing process. (B) Drawing speed used to control the stress within the fiber. (C) Resulting fiber diameter correlated to the drawing speed and stress.
fig. S2. Optical transmission spectra of PC/COC fibers at visible wavelengths. (A) Normalized absorption spectra of the PC core and COC cladding fibers and pure PC fibers. (B) Transmission at a wavelength λ = 473 nm for pure PC (1.11 db/cm), PC/COC (0.97 db/cm), and PC/COC (0.97 db/cm) fibers coated with poly(dimethylsiloxane) (PDMS) as a function of length. Loss coefficients for the devices are indicated on the plot. Error bars represent standard error of the mean (s.e.m.). Number of samples is n = 5. fig. S3. Transmission at a wavelength λ = 473 nm for COCE fiber. Loss coefficient is indicated on the plot. Error bars represent standard error of the mean (s.e.m.). Number of samples is n = 3.
fig. S4. Impedance of COCE fibers coated with a single layer of AgNW mesh and measured at 0, 10, and 20% extension strain. Inset: scanning electron microscope (SEM) images of the COCE/AgNW/PDMS fibers under 0%, 10%, and 20% strain.
fig. S5. Spontaneous single units isolated during acute anesthetized recordings (see Fig. 5, C to F). (A, B) Principal component analysis (A) and the corresponding interspike interval histogram (B) for the unit recorded using a flexible probe with a PC/COC core (raw electrophysiological data and action potential shape are shown in Fig. 5C, D of the manuscript). (C, D) Principal component analysis (C) and the corresponding interspike interval histogram (D) for the unit recorded using a stretchable probe with a COCE core (raw electrophysiological data and action potential shape are shown in Fig. 5E, F of the manuscript).
fig. S6. Electrophysiological recording collected from the freely moving mice implanted with fiber probes. Electrophysiological recordings collected during tethered free behavior one day (A, B) and one week (C, D) following implantation. The recordings were performed using AgNW mesh electrodes within flexible probes with PC/COC cores (A, C) and within stretchable probes with COCE cores. Individual neuron action potentials could not be isolated due to the presence of movement artifacts.
fig. S7. Additional in vivo sensory and electromyographic recordings. (A) Sensory evoked potentials (SEPs) recorded similar to Fig. 5G, except the polarity of the biphasic stimulus waveform was reversed as a control. The comparable shapes of the SEPs suggest that stimulus artifact did not significantly affect the sensory recording. (B) SEP recruitment curve of the area under the first positive peaks of recordings shown in (A). (C) Electromyography (EMG) of the gastrocnemius caused by high-frequency optical stimulation (wavelength λ = 473 m, 125 mw/mm 2, 5 ms pulse width, 100 Hz) applied to the spinal cord. In comparison to 10 Hz stimulation (Fig. 5K), the EMG response does not follow each optical pulse due to the kinetics of ChR2. Interestingly, the EMG response in this example increases over time, indicating that the motor system is far from linear time-invariant.
fig. S8. Electrophysiological recordings of optically stimulated activity. (A) Neural activity recorded acutely in the spinal cord of a Thy1-ChR2-YFP mouse stimulated with laser pulses (wavelength λ = 473 nm, 168 mw/mm2, 5 ms pulse width, 100 Hz) delivered through the PC/COC fiber and recorded with the concentric AgNW mesh electrodes. (B) Neural activity recorded acutely in the spinal cord of a Thy1-ChR2-YFP mouse stimulated with laser pulses (wavelength λ = 473 nm, 125 mw/mm2, 5 ms pulse width, 100 Hz) delivered through the COCE fiber and recorded with the concentric AgNW mesh electrodes.
fig. S9. In vivo EMG recordings. (A) EMG signals evoked in Thy1-ChR2-YFP mice by optical stimulation (wavelength λ = 473 nm, 5 ms pulse width, 2 Hz) of the lumber spinal cord via a COCE fiber (size: 200 200 μm2) inserted 300 µm deep into the cord. The delayed EMG response to optical excitation for lower excitation powers is consistent with the commonly accepted ChR2 activation threshold of 1 mw/mm2. Specifically, for lower optical powers the amount of light reaching motor pools is insufficient to activate ChR2-mediated firing, and the observed delayed EMG response is likely a result of sensory feedback. Higher optical powers enable direct activation of motor neurons, and a low-latency EMG response is observed. (B) EMG recruitment curve relating the rectified EMG area in (A) to the optical power. (C) Electromyography (EMG) of the gastrocnemius caused by high-frequency optical stimulation (wavelength λ = 473 m, 125 mw/mm2, 5 ms pulse width, 100 Hz) applied to the spinal cord. In comparison to 10 Hz stimulation (Fig. 5K), the EMG response does not follow each optical pulse due to the kinetics of ChR2. Interestingly, the EMG response in this example increases over time, indicating that the motor system is far from linear time-invariant.
fig. S10. Immunohistochemical analysis of the dorsal horn 2 weeks after device implantation surgeries. GFAP (green) marks astrocytes, and NeuN (red) labels neurons. Scale bar is 100 μm. (A) Confocal micrographs of a transverse section of the lumbar spinal cord without an implant. (B) Transverse section of the lumbar spinal cord from a mouse implanted with a PC/COC/AgNW/PDMS probe for two weeks. The device was positioned on the spinal cord surface. (C) Confocal micrographs of a transverse section of the lumbar spinal cord from a mouse implanted with a PC/COC/AgNW/PDMS probe for two weeks. The device was positioned on the spinal cord surface. (D) Transverse section of the lumbar spinal cord from a mouse implanted with a PC/COC/AgNW/PDMS probe for two weeks. The device was inserted into the spinal cord. (E) Confocal micrographs of a transverse section of the lumbar spinal cord from a mouse implanted with a PC/COC/AgNW/PDMS probe for two weeks. The device was inserted into the spinal cord. No tissue erosion and negligible astrocyte proliferation were observed. video S1. Optical spinal control of muscle activity. Optical pulses (5 ms, 168 mw/mm 2 ) delivered to the lumbar region of the spinal cord of a Thy1-ChR2-YFP transgenic mouse through the cores of the PC/COC/AgNW/PDMS fiber probes evoke twitch muscle contractions at 10 and 100 Hz.