Influence of the Surface Material and Illumination upon the Performance of a Microelectrode/Electrolyte Interface in Optogenetics

doi:10.3390/mi12091061

. 2021 Aug 31;12(9):1061.

doi: 10.3390/mi12091061.

Influence of the Surface Material and Illumination upon the Performance of a Microelectrode/Electrolyte Interface in Optogenetics

Junyu Shen¹, Yanyan Xu¹, Zhengwen Xiao¹, Yuebo Liu¹, Honghui Liu¹, Fengge Wang¹, Wanqing Yao¹, Zhaokun Yan¹, Minjie Zhang¹, Zhisheng Wu^{1

2}, Yang Liu^{1

2}, Sio Hang Pun³, Tim C Lei⁴, Mang I Vai^{3

5}, Peng Un Mak⁵, Changhao Chen³, Baijun Zhang^{1

2}

Affiliations

¹ School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China.
² State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China.
³ State Key Laboratory of Analog and Mixed-Signal VLSI, Institute of Microelectronics, University of Macau, Macau 999078, China.
⁴ Department of Electrical Engineering, University of Colorado Denver, Denver, CO 80204, USA.
⁵ Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau 999078, China.

PMID: 34577704
PMCID: PMC8471589
DOI: 10.3390/mi12091061

Influence of the Surface Material and Illumination upon the Performance of a Microelectrode/Electrolyte Interface in Optogenetics

Junyu Shen et al. Micromachines (Basel). 2021.

. 2021 Aug 31;12(9):1061.

doi: 10.3390/mi12091061.

Authors

Affiliations

¹ School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China.
² State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China.
³ State Key Laboratory of Analog and Mixed-Signal VLSI, Institute of Microelectronics, University of Macau, Macau 999078, China.
⁴ Department of Electrical Engineering, University of Colorado Denver, Denver, CO 80204, USA.
⁵ Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau 999078, China.

PMID: 34577704
PMCID: PMC8471589
DOI: 10.3390/mi12091061

Abstract

Integrated optrodes for optogenetics have been becoming a significant tool in neuroscience through the combination of offering accurate stimulation to target cells and recording biological signals simultaneously. This makes it not just be widely used in neuroscience researches, but also have a great potential to be employed in future treatments in clinical neurological diseases. To optimize the integrated optrodes, this paper aimed to investigate the influence of surface material and illumination upon the performance of the microelectrode/electrolyte interface and build a corresponding evaluation system. In this work, an integrated planar optrode with a blue LED and microelectrodes was designed and fabricated. The charge transfer mechanism on the interface was theoretically modeled and experimentally verified. An evaluation system for assessing microelectrodes was also built up. Using this system, the proposed model of various biocompatible surface materials on microelectrodes was further investigated under different illumination conditions. The influence of illumination on the microelectrode/electrolyte interface was the cause of optical artifacts, which interfere the biological signal recording. It was found that surface materials had a great effect on the charge transfer capacity, electrical stability and recoverability, photostability, and especially optical artifacts. The metal with better charge transfer capacity and electrical stability is highly possible to have a better performance on the optical artifacts, regardless of its electrical recoverability and photostability under the illumination conditions of optogenetics. Among the five metals used in our investigation, iridium served as the best surface material for the proposed integrated optrodes. Thus, optimizing the surface material for optrodes could reduce optical interference, enhance the quality of the neural signal recording for optogenetics, and thus help to advance the research in neuroscience.

Keywords: microelectrode/electrolyte interface; optical artifact; optogenetics; optrode; photostability; surface material.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

**Figure A1**
5 μm × 5 μm AFM images of microelectrodes made of (a) Ti, (b) Cr, (c) Au, (d) Pt, (e) Ir.

**Figure 1**
(a) Top view and (b) cross-sectional view of the monolithic integrated planar optrode. (c) The picture of the proposed encapsulated integrated planar optrode. (d) The micrograph of the top area and (e) the micrograph of the wire-bonded area on the optrode.

**Figure 2**
(a) Theoretical model for the charge transfer mechanism on the microelectrode/electrolyte interface, in which the upper part displays faradaic processes and the lower part an EDL capacitor. (b) Equivalent circuit for the charge transfer mechanism on the interface.

**Figure 3**
(a) The proposed testing system for electrical characterizations with a semiconductor device analyzer or LCR meter in PBS with shielding. (b) The testing system for optical artifacts with amplifier and data acquisition card in PBS with shielding, while the optical artifacts are generated by a light-emitting diode driven by a pulse generator.

**Figure 4**
Electrochemical impedance spectroscopy (EIS) of microelectrodes with different surface materials, including Ti, Cr, Au, Pt and Ir.

**Figure 5**
(a) Experimental values and fitting result of Z_M/E versus C_d (V_Ref = 0 and V_Level = 50 mV at 1 kHz). The insert is the C_d-V_Ref curve of microelectrodes with different surface materials measured within the range of −50 to 50 mV, representing the EDL capacitor. (b) Z_M/E-V_Ref curves of microelectrodes with different surface materials measured within the range of 0 to 500 mV, characterizing the critical values and electrical stability of faradaic processes. (c) Z_M/E values of microelectrodes with different surface materials measured before and after the faradaic processes (V_Ref = 0 and V_Level = 50 mV at 1 kHz).

**Figure 6**
The change of C_d versus the wavelength (V_Ref = 0 and V_Level = 50 mV at 1 kHz) of microelectrodes caused by different surface materials.

**Figure 7**
(a) The optical signal used in the testing system and the recorded optical artifacts of optrodes made by different surface materials, including (b) Ti, (c) Cr, (d) Au, (e) Pt, (f) Ir.

**Figure 8**
The correlation analyses between optical artifacts and (a) Z_M/E, (b) the critical value V_c, (c) C_d and (d) the growth rate of C_d, respectively.

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References

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1. Zhang F., Aravanis A.M., Adamantidis A., Lecea L.D., Deisseroth K. Circuit-breakers: Optical technologies for probing neural signals and systems. Nat. Rev. Neurosci. 2007;8:577–581. doi: 10.1038/nrn2192. - DOI - PubMed
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[1] Yizhar O., Fenno L.E., Davidson T.J., Mogri M., Deisseroth K. Optogenetics in neural systems. Neuron. 2011;71:9–34. doi: 10.1016/j.neuron.2011.06.004. - DOI - PubMed

[2] Yizhar O., Fenno L.E., Davidson T.J., Mogri M., Deisseroth K. Optogenetics in neural systems. Neuron. 2011;71:9–34. doi: 10.1016/j.neuron.2011.06.004. - DOI - PubMed

[3] Zhang F., Aravanis A.M., Adamantidis A., Lecea L.D., Deisseroth K. Circuit-breakers: Optical technologies for probing neural signals and systems. Nat. Rev. Neurosci. 2007;8:577–581. doi: 10.1038/nrn2192. - DOI - PubMed

[4] Zhang F., Aravanis A.M., Adamantidis A., Lecea L.D., Deisseroth K. Circuit-breakers: Optical technologies for probing neural signals and systems. Nat. Rev. Neurosci. 2007;8:577–581. doi: 10.1038/nrn2192. - DOI - PubMed

[5] Seymour J.P., Wu F., Wise K.D., Yoon E. State-of-the-art MEMS and microsystem tools for brain research. Microsyst. Nanoeng. 2017;3:16066. doi: 10.1038/micronano.2016.66. - DOI - PMC - PubMed

[6] Seymour J.P., Wu F., Wise K.D., Yoon E. State-of-the-art MEMS and microsystem tools for brain research. Microsyst. Nanoeng. 2017;3:16066. doi: 10.1038/micronano.2016.66. - DOI - PMC - PubMed

[7] Mickle A.D., Gereau R.W. A bright future? Optogenetics in the periphery for pain research and therapy. Pain. 2018;159((Suppl. 1)):S65–S73. doi: 10.1097/j.pain.0000000000001329. - DOI - PMC - PubMed

[8] Mickle A.D., Gereau R.W. A bright future? Optogenetics in the periphery for pain research and therapy. Pain. 2018;159((Suppl. 1)):S65–S73. doi: 10.1097/j.pain.0000000000001329. - DOI - PMC - PubMed

[9] Sahel J.-A., Boulanger-Scemama E., Pagot C., Arleo A., Galluppi F., Martel J.N., Esposti S.D., Delaux A., de Saint Aubert J.-B., de Montleau C., et al. Partial recovery of visual function in a blind patient after optogenetic therapy. Nat. Med. 2021;27:1223–1229. doi: 10.1038/s41591-021-01351-4. - DOI - PubMed

[10] Sahel J.-A., Boulanger-Scemama E., Pagot C., Arleo A., Galluppi F., Martel J.N., Esposti S.D., Delaux A., de Saint Aubert J.-B., de Montleau C., et al. Partial recovery of visual function in a blind patient after optogenetic therapy. Nat. Med. 2021;27:1223–1229. doi: 10.1038/s41591-021-01351-4. - DOI - PubMed

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Influence of the Surface Material and Illumination upon the Performance of a Microelectrode/Electrolyte Interface in Optogenetics

Affiliations

Influence of the Surface Material and Illumination upon the Performance of a Microelectrode/Electrolyte Interface in Optogenetics

Authors

Affiliations

Abstract

Conflict of interest statement

Figures

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Cited by

References

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