Continuous-wave near-infrared stimulated-emission depletion microscopy using downshifting lanthanide nanoparticles

Stimulated-emission depletion (STED) microscopy has profoundly extended our horizons to the subcellular level(1-3). However, it remains challenging to perform hours-long, autofluorescence-free super-resolution imaging in near-infrared (NIR) optical windows under facile continuous-wave laser depletion at low power(4,5). Here we report downshifting lanthanide nanoparticles that enable background-suppressed STED imaging in all-NIR spectral bands (lambda(excitation) = 808 nm, lambda(depletion) = 1,064 nm and lambda(emission) = 850-900 nm), with a lateral resolution of below 20 nm and zero photobleaching. With a quasi-four-level configuration and long-lived (tau > 100 mu s) metastable states, these nanoparticles support near-unity (98.8%) luminescence suppression under 19 kW cm(-2) saturation intensity. The all-NIR regime enables high-contrast deep-tissue (similar to 50 mu m) imaging with approximately 70 nm spatial resolution. These lanthanide nanoprobes promise to expand the application realm of STED microscopy and pave the way towards high-resolution time-lapse investigations of cellular processes at superior spatial and temporal dimensions.

Automated summary

This study introduces downshifting lanthanide nanoparticles that enable background-suppressed STED imaging in all-NIR spectral bands, providing high resolution and zero photobleaching effects, allowing for high-contrast deep-tissue imaging.