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“Look” inside the biological samples using an ultrafast optical clearing method

2019-06-06

Most biological tissue is opaque, and the inside fine structures are invisible even with a microscope. The research team led by GONG Wei, a research fellow with the Center for Neuroscience at the School of Medicine developed an ultrafast optical clearing method (FOCM) with simple protocols and common reagents to enable us to “see” these structures more quickly. Their findings are published in the May 18 issue of the journal of PNAS.

Optical clearing is a versatile approach to improve imaging quality and depth of optical microscopy by reducing scattered light. However, conventional optical clearing methods are restricted in the efficiency-first applications due to dissatisfactory time consumption, irreversible tissue deformation, and fluorescence quenching.

The FOCM can clarify 300-µm-thick brain slices within 2 min without morphological distortion. Besides, the tissue linear expansion can be well controlled by only a 2.12% increase, meanwhile the fluorescence signals of GFP can be preserved up to 86% even after 11 d. The FOCM can also help build the detailed 3D nerve cells model and show the connection between neuron, astrocyte, and blood vessel. When applied to 3D imaging analysis, the foot shock and morphine stimulation can induce distinct c-fos pattern in the paraventricular nucleus of the hypothalamus (PVH). Moreover, thanks to cheap reagents and easy operation, it shows great potential to be a widely-used sample mounting medium for biological optical imaging.

This research enjoys massive acclaim from experts. Comments include “This method may well produce a huge impact on large-scale anatomical analysis of brain connctome” and “Compared with other clearing methods, this method can significantly reduce the fabrication time, remarkably preserve fluorescence and effectively improve the depth of imaging.”

In video

FOCM realized a fast optical clearing within 2 minutes.

3D visualization of C57BL/6 mouse brain slices immunostained for astrocyte

3D visualization of C57BL/6 mouse brain slices immunostained for microglia

3D visualization of Thy1-GFP-M mouse brain slices immunostained for the blood vessel (red) and astrocytes (silver)