Achieving low-power single-wavelength-pair nanoscopy with NIR-II continuous-wave laser for multi-chromatic probes

Abstract

Stimulated emission depletion (STED) microscopy is a powerful diffraction-unlimited technique for fluorescence imaging. Despite its rapid evolution, STED fundamentally suffers from high-intensity light illumination, sophisticated probe-defined laser schemes, and limited photon budget of the probes. Here, we demonstrate a versatile strategy, stimulated-emission induced excitation depletion (STExD), to deplete the emission of multi-chromatic probes using a single pair of low-power, near-infrared (NIR), continuous-wave (CW) lasers with fixed wavelengths. With the effect of cascade amplified depletion in lanthanide upconversion systems, we achieve emission inhibition for a wide range of emitters (e.g., Nd3+, Yb3+, Er3+, Ho3+, Pr3+, Eu3+, Tm3+, Gd3+, and Tb3+) by manipulating their common sensitizer, i.e., Nd3+ ions, using a 1064-nm laser. With NaYF4:Nd nanoparticles, we demonstrate an ultrahigh depletion efficiency of 99.3 ± 0.3% for the 450 nm emission with a low saturation intensity of 23.8 ± 0.4 kW cm−2. We further demonstrate nanoscopic imaging with a series of multi-chromatic nanoprobes with a lateral resolution down to 34 nm, two-color STExD imaging, and subcellular imaging of the immunolabelled actin filaments. The strategy expounded here promotes single wavelength-pair nanoscopy for multi-chromatic probes and for multi-color imaging under low-intensity-level NIR-II CW laser depletion.

Upconversion nanoparticles for super-resolution quantification of single small extracellular vesicles

“…Lanthanide-doped upconversion nanoparticles (UCNPs) has been discovered with nonlinear photoswitchable properties, and suitable for STED-like superresolution nanoscopy with sub-30 nm optical resolution in resolving the cluster of single UCNPs [22]. It has been further demonstrated to imaging cytoskeleton structures [23], actin fibres [24], actin filaments [25] of Hela cells, sub-cellular structures of neuronal cells [26], and even deep tissues [27,28]. Compared with the conventional dyes used in STED, a number of so-discovered new nonlinear optical properties can typically reduce the excitation power density by over three orders of magnitude, in the range of 10 5 W/cm 2 .…”

Recent Development in Sensitizers for Lanthanide-Doped Upconversion Luminescence

“…Thus, exploration of new sensitizers with large absorption cross sections and high energy transfer efficiencies to activators still remains promising. From the widened concept point of view where any luminescent entity may work as sensitizers, development of new sensitizers and corresponding modulation principles beyond the above-discussed may not only facilitate disclosure of brand-new UCL profiles, it will also push forward discovery of novel energy transfer mechanisms and characteristic applications. Advances of UCL can be greatly driven by the demand from practical applications. Thus, exploration of conceptually new applications beyond currently prevalent ones, such as remote temperature sensing, bioimaging, theranostics, anti-counterfeiting, display, and so on, shall surely push forward the development of new sensitizers (and activators), for example, optical tweezers, optical cooling, thermal photovoltaics, optogenetics, super-resolution multicolor nanoscopic imaging, in situ motor protein tracking and machine learning, as well as information encryption and deep learning decoding. − Some common but long-lasting issues, such as the temporal behavior of sensitizer (and activator) ions during the excitation and emission processes, tunable UCL with intense and single emission, improvement of the quantum efficiency, standardization of UCL measurement (e.g., excitation power density, emission intensity, lifetime, etc. ), and so forth, need also to be clarified toward arbitrary UCL modulation and commercial applications. , …”

“…Advances of UCL can be greatly driven by the demand from practical applications. Thus, exploration of conceptually new applications beyond currently prevalent ones, such as remote temperature sensing, bioimaging, theranostics, anti-counterfeiting, display, and so on, shall surely push forward the development of new sensitizers (and activators), for example, optical tweezers, optical cooling, thermal photovoltaics, optogenetics, super-resolution multicolor nanoscopic imaging, in situ motor protein tracking and machine learning, as well as information encryption and deep learning decoding. − …”

Solvatochromic Near-Infrared Aggregation-Induced Emission-Active Acrylonitriles by Acceptor Modulation for Low-Power Stimulated Emission Depletion Nanoscopy

“…Some technique achievements, such as time-gated detection and double depletion, etc., have been reported to decrease the depletion power for STED nanoscopy. − Nevertheless, there is a long way for these techniques to be promoted. Hence, developing fluorescent materials for STED super-resolution imaging is a straightforward and convenient strategy.…”