For centuries, optical microscopy has greatly advanced our understanding of the micro world. But super-resolution techniques have practical limitations when imaging nano-scale dynamics in living cells and other biological samples. For example, they require acquisition times spanning from a few seconds to several hours and more than 100,000 times higher illumination intensity than sunlight. This has led to slow imaging speeds and caused great damage to biological samples, so super-resolution live imaging at high speeds is still challenging.
Cellular organelles interact with one another and the cytoskeleton to carry out various physiological functions. Visualizing these interactions requires noninvasive, long duration imaging of the intracellular environment at high spatiotemporal resolution, and low background. To achieve these contradicting goals, Dong Li, a professor at the Institute of Biophysics, Chinese Academy of Sciences, developed grazing incidence structured illumination microscopy (GI-SIM) that achieves a spatial resolution of 95 nm at a frame rate of 266 Hz for hundreds to thousands of frames. Compared to commonly used TIRF/TIRF-SIM techniques, GI-SIM probes ~10× further beyond the basal cell membrane and collects ~10× greater fluorescence signals. Compared to spinning disk confocal microscopy, GI-SIM achieves ~2× better spatial resolution and ~10× faster imaging speeds. Compared to other super-resolution (SR) methods, GI-SIM achieves sub-100 nm resolution over cellular-sized fields of view at ~100× faster speed over ~10-100 fold as many frames.
These optical imaging techniques fulfill unmet needs for imaging intracellular dynamics with ultra-high spatial and temporal resolution with minimal invasiveness, therefore opening a new window for the study of minute, highly dynamic interactions within cultured cells or multicellular organisms. Li and his team are now further pushing the envelope of super-resolution live imaging, enabling researchers to see the biological processes in intact tissues or multicellular organisms.