A near-infrared genetically encoded calcium indicator for in vivo imaging.

Nature biotechnology 2021 Mar

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While calcium imaging has become a mainstay of modern neuroscience, the spectral properties of current fluorescent calcium indicators limit deep-tissue imaging as well as simultaneous use with other probes. Using two monomeric near-infrared (NIR) fluorescent proteins (FPs), we engineered an NIR Förster resonance energy transfer (FRET)-based genetically encoded calcium indicator (iGECI). iGECI exhibits high levels of brightness and photostability and an increase up to 600% in the fluorescence response to calcium. In dissociated neurons, iGECI detects spontaneous neuronal activity and electrically and optogenetically induced firing. We validated the performance of iGECI up to a depth of almost 400 µm in acute brain slices using one-photon light-sheet imaging. Applying hybrid photoacoustic and fluorescence microscopy, we simultaneously monitored neuronal and hemodynamic activities in the mouse brain through an intact skull, with resolutions of ~3 μm (lateral) and ~25-50 μm (axial). Using two-photon imaging, we detected evoked and spontaneous neuronal activity in the mouse visual cortex, with fluorescence changes of up to 25%. iGECI allows biosensors and optogenetic actuators to be multiplexed without spectral crosstalk.

Citation

Anton A Shemetov, Mikhail V Monakhov, Qinrong Zhang, Jose Ernesto Canton-Josh, Manish Kumar, Maomao Chen, Mikhail E Matlashov, Xuan Li, Wei Yang, Liming Nie, Daria M Shcherbakova, Yevgenia Kozorovitskiy, Junjie Yao, Na Ji, Vladislav V Verkhusha. A near-infrared genetically encoded calcium indicator for in vivo imaging. Nature biotechnology. 2021 Mar;39(3):368-377