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Séminaire impromptu - Liangyi CHENHigh spatiotemporal resolution fluorescence imaging of biological samples in vivo

Abstract :

 Here we will present two pieces of high-resolution fluorescence microscopy methods we invented for live sample imaging.
The first one is for in vivo imaging, which is a fast, high-resolution, miniaturized two-photon microscope (FHIRM-TPM). With a headpiece weighing 2.15 g and a new type of hollow-core photonic crystal fiber to deliver 920-nm femtosecond laser pulses, the FHIRM-TPM is capable of imaging commonly used biosensors at high spatiotemporal resolution (0.64 μm laterally and 3.35 μm axially, 40 Hz at 256 × 256 pixels). It compares favorably with benchtop two-photon microscopy and miniature wide-field fluorescence microscopy in the structural and functional imaging of Thy1-GFP- or GCaMP6f-labeled neurons. Further, we demonstrate its unique application and robustness with hour-long recording of neuronal activities down to the level of spines in mice engaging in social interaction.

The second method is for live cell long-term super-resolution (SR) imaging. We have developed a deconvolution algorithm for structured illumination microscopy based on Hessian matrixes (Hessian-SIM). It uses the continuity of biological structures in multiple dimensions as a priori knowledge to guide image reconstruction and attains artifact-minimized SR images with less than 10% of the photon dose used by conventional SIM while substantially outperforming current algorithms at low signal intensities. Hessian-SIM enables rapid imaging of moving vesicles or loops in the endoplasmic reticulum without motion artifacts and with a spatiotemporal resolution of 88 nm and 188 Hz. Its high sensitivity allows the use of sub-millisecond excitation pulses followed by dark recovery times to reduce photobleaching of fluorescent proteins, enabling hour-long time-lapse SR imaging in live cells.

Scientific focus :

Dr. Liangyi Chen is a professor and principal investigator in Institute of Molecular Medicine, Peking University. His current research interests are focused on development of novel high spatiotemporal fluorescence imaging techniques for in vivo studies. His lab also use these new technologies to study blood glucose regulation and the pathological process underlying diabetes progression, using both Zebrafish and mouse models. As the corresponding author, Dr. Liangyi Chen has published papers in peer-reviewed journals such as Nature Biotechnology, Nature Methods, Cell Res., Proc Natl Acad Sci U S A., Biophys J., Diabetes and Diabetologia, etc. He has been served as a senior faculty member in the Neuronal Signaling Mechanisms Section in Faculty of 1000 Biology since 2012. He has been invited to give talks in international conferences hosted by academic societies such as OSA, SPIE and Biophysical Society, etc.