Achieving high-efficiency emission depletion nanoscopy by employing cross relaxation in upconversion nanoparticles

Qiuqiang Zhan,Xingyun Peng,Rui Pu,Hans Ågren,Bingru Huang,Haichun Liu,Chao Zhou,Baoju Wang,Qiusheng Wu,Sailing He

doi:10.1038/s41467-017-01141-y

Abstract

Stimulated emission depletion microscopy provides a powerful sub-diffraction imaging modality for life science studies. Conventionally, stimulated emission depletion requires a relatively high light intensity to obtain an adequate depletion efficiency through only light–matter interaction. Here we show efficient emission depletion for a class of lanthanide-doped upconversion nanoparticles with the assistance of interionic cross relaxation, which significantly lowers the laser intensity requirements of optical depletion. We demonstrate two-color super-resolution imaging using upconversion nanoparticles (resolution ~ 66 nm) with a single pair of excitation/depletion beams. In addition, we show super-resolution imaging of immunostained cytoskeleton structures of fixed cells (resolution ~ 82 nm) using upconversion nanoparticles. These achievements provide a new perspective for the development of photoswitchable luminescent probes and will broaden the applications of lanthanide-doped nanoparticles for sub-diffraction microscopic imaging.

Highlights

Stimulated emission depletion microscopy provides a powerful sub-diffraction imaging modality for life science studies
This approach has led to many far-field super-resolution fluorescence microscopy techniques, such as stimulated emission depletion microscopy (STED)[14,15,16], single-molecule localization nanoscopy[17,18,19], and saturated structured illumination microscopy[20, 21], which breaks the diffraction limit and makes it possible to image at a spatial resolution of down to a few nanometers
In our previous study on another upconversion system (NaYF4:Yb3+, Er3+), the first optical depletion of Er3+ emission was shown by inducing excited-state absorption (ESA), intrinsically different from the mechanism we propose in the present study, but the efficiency needed improvement for applications[27]

Summary

Introduction

Stimulated emission depletion microscopy provides a powerful sub-diffraction imaging modality for life science studies. Exploitation of optical switching to control the transition of luminophores between two optically distinguishable states (on/off) is an exciting and popular way to circumvent the diffraction limit[11,12,13] This approach has led to many far-field super-resolution fluorescence microscopy techniques, such as stimulated emission depletion microscopy (STED)[14,15,16], single-molecule localization nanoscopy (such as PALM/STORM and MINFLUX)[17,18,19], and saturated structured illumination microscopy[20, 21], which breaks the diffraction limit and makes it possible to image at a spatial resolution of down to a few nanometers. Error bars represent ± 1 s.d. g The power-dependent depletion efficiency and the background 455-

Methods

Results

Conclusion