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A new three-dimensional super-resolution imaging technique for live cells

2018-12-10

Recently, the research team led by Prof. LIU Xu and Prof. KUANG Cuifang from the College of Optical Science and Engineering put forward a novel method of performing 3D multi-color live-cell super-resolution volume imaging termed as multi-angle interference microscopy (MAIM), thus offering a powerful device for researches intothe subcellular dynamics of mitochondria and microtubule architectures during cell migration. This finding is published in the November 16 issue of Nature Communications.

Inspired by the Nobel Prize

The Nobel Prize in Chemistry 2014 was awarded jointly to Eric Betzig, Stefan W. Hell and William E. Moerner“for the development of super-resolved fluorescence microscopy.”This technique overcomes the resolution limit of standard optical microscopy and enablesnanoscale imaging of living tissueand innumerable benefits for life sciences and for society. However, it has its own flaws. For example, it is difficult to use for imaging and tracking the real-time evolution of living cells in a large field of view because of the requirements of high excitation intensities of 103–108 W cm−2 (far beyond the safe intensity of 0.1 W cm−2for live-cell imaging), specialized fluorophores and labeling strategies, and a long imaging capturing process.

Meanwhile, althoughthe aforementioned shortcomings can be overcome by 3D structured illumination microscopy (3D SIM), which can image 3D living samples labeled by conventional dyes with an excitation intensity of 1–10 W cm−2, the limited spatial resolution, which is typically improved two fold or less in lateral and axial resolutions, poses a barrier to its biological applications.

Thus, it has become a hard nut to crack for researchers as to how to remedy existing blemishes and how to capture the subcellular dynamics of living cells.

Exploring theprinciple of life through a new lens

Inspired by these challenges, the research team designs and implements a technique for 3D multi-color live-cell super-resolution volume imaging by incorporating SIM with multi-angle evanescent light illumination, termed as MAIM.

The resolution for a standard optical microscope in the visible light spectrum is 250-300 nm laterally and 500-600 nm axially. On this basis, structured illumination microscopy doubles resolution on an axial and lateral scale down.MAIM can map the surface morphology with a sub-100-nm lateral resolution and axial architectures with an approximately 40-nm axial resolution over a 600-nm depth volume.

In terms of temporal resolution, compared with other 3D super-resolution techniques, MAIM is blessed with an exceptional advantage because of the smaller number of required raw images. Moreover, a lower requirement for the surface energy density of the illumination light, which is even lower than that of 3D SIM, enables its use for probing specific long-term dynamics in living cells without photodamage or photobleaching.

3D rapid super-resolution imaging of organelle near the cellular membrane opens the door to subcellular studies, thereby helping reveal the intrinsic features of life, Prof. LIU Xu observes. 

In the past, researchers had to understand the therapeutic effects of a particular drug through an overall result, but in the future, MAIM can be applied to track the subcellular dynamics of mitochondria and microtubule architectures, thus boosting the efficiency of various studies spectacularly, Prof. Liu adds.