Nanosilver-Enhanced Far-Field Fluorescence Fluctuations for Super-Resolution Microscopy.

Fluctuation-based super-resolution microscopy enhances image resolution using signal fluctuations, yet the inherent fluctuations of fluorophores limit its spatiotemporal resolution. In this work, we reveal a far-field enhancement (FFE) effect via a nanosilver film that significantly boosts fluorescence fluctuations of fluorophores positioned up to 10 μm away. The FFE effect arises from the interference of scattered light from the nanosilver film and photothermal-induced refractive index changes in the imaging medium, which create periodic auxiliary illumination on the sample. This phenomenon enabled the development of far-field enhanced super-resolution microscopy (FFE-SRM), a technique compatible with commonly used fluorophores. FFE-SRM improves temporal resolution up to 10-fold and enhances spatial resolution by about 2-fold over various SRM methods, including stochastic optical fluctuation imaging, super-resolution radial fluctuation, mean-shift super-resolution, and direct stochastic optical reconstruction microscopy. We demonstrated the potential of FFE-SRM by revealing mitochondrial dynamics in live-cell imaging, advancing super-resolution imaging, and cellular process exploration.