title: Quasi-Continuous Wave Near-Infrared Excitation of Upconversion Nanoparticles for Optogenetic Manipulation of C. elegans.
abstract: Optogenetics is an emerging powerful tool to investigate workings of the nervous system. However, the use of low tissue penetrating visible light limits its therapeutic potential. Employing deep penetrating near-infrared (NIR) light for optogenetics would be beneficial but it cannot be used directly. This issue can be tackled with upconversion nanoparticles (UCNs) acting as nanotransducers emitting at shorter wavelengths extending to the UV range upon NIR light excitation. Although attractive, implementation of such NIR-optogenetics is hindered by the low UCN emission intensity that necessitates high NIR excitation intensities, resulting in overheating issues. A novel quasi-continuous wave (quasi-CW) excitation approach is developed that significantly enhances multiphoton emissions from UCNs, and for the first time NIR light-triggered optogenetic manipulations are implemented in vitro and in C. elegans. The approach developed here enables the activation of channelrhodopsin-2 with a significantly lower excitation power and UCN concentration along with negligible phototoxicity as seen with CW excitation, paving the way for therapeutic optogenetics.
authors: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 117583, Singapore.|NUS Graduate School for Integrative Sciences & Engineering, National University of Singapore, 117456, Singapore.
authors: Akshaya
authors: A
authors: Bansal
authors: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 117583, Singapore.
authors: Haichun
authors: H
authors: Liu
authors: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 117583, Singapore.
authors: Muthu Kumara Gnanasammandhan
authors: MK
authors: Jayakumar
authors: Biophotonics Group, Department of Physics, Lund University, P.O. Box 118, SE-22100, Lund, Sweden.
authors: Stefan
authors: S
authors: Andersson-Engels
authors: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 117583, Singapore.|NUS Graduate School for Integrative Sciences & Engineering, National University of Singapore, 117456, Singapore.
authors: Yong
authors: Y
authors: Zhang
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism* / Q000528:radiation effects*; D000075402:Channelrhodopsins; D005453:Fluorescence; D057809:HEK293 Cells; D006801:Humans; D007259:Infrared Rays; D036641:Microscopy, Fluorescence, Multiphoton; D053758:Nanoparticles / Q000737:chemistry*; D062308:Optogenetics / Q000379:methods*; D013816:Thermodynamics
chemical_list: D000075402:Channelrhodopsins
keywords: nanoparticles; near-infrared; optogenetics; quasi-CW; upconversion