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Targeted and efficient activation of channelrhodopsins expressed in living cells via specifically-bound upconversion nanoparticles

Abstract

Optogenetics is an innovative technology now widely adopted by researchers in different fields of the biological sciences. However, most light-sensitive proteins adopted in optogenetics are excited by ultra-violet or visible light which has a weak tissue penetration capability. Upconversion nanoparticles (UCNPs), which absorb near-infrared (NIR) light to emit shorter wavelength light, can help address this issue. In this report, we demonstrated the target selectivity by specifically conjugating the UCNPs with channelrhodopsin-2 (ChR2). We tagged V5 epitope to the extracellular N-terminal of ChR2 (V5-ChR2m) and functionalized the surface of UCNP with NeutrAvidin (NAv-UCNPs). After the binding of biotinylated antibody against V5 onto the V5-ChR2m expressed in the plasma membrane of live HEK293T cells, our results showed that the NAv-UCNPs were specifically bound to the membrane of cells expressing V5-ChR2m. Without the V5 epitope or NAv modification, no binding of UCNPs onto the cell membrane was observed. For the cells expressing V5-ChR2m and bound with NAv-UCNP, both 488 nm illumination and the upconverted blue emission from UCNP by 980 nm excitation induced an inward current and elevated the intracellular Ca2+ concentration. Our design reduces the distance between UCNP and light-sensitive protein to a molecular level, which not only minimizes the NIR energy required but also provides a way to guide the specific binding for optogenetics applications. Keywords: optogenetics, channelrhodopsin, near-infrared, upconversion nanoparticles, target selectivity  

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Publication details

The article was received on 08 May 2017, accepted on 04 Jun 2017 and first published on 07 Jun 2017


Article type: Paper
DOI: 10.1039/C7NR03246C
Citation: Nanoscale, 2017, Accepted Manuscript
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    Targeted and efficient activation of channelrhodopsins expressed in living cells via specifically-bound upconversion nanoparticles

    K. Yadav, A. Chou, R. K. Ulaganathan, H. Gao, H. Lee, C. Pan and Y. Chen, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR03246C

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