Open AccessSimultaneous super-linear excitation-emission and emission depletion allows imaging of upconversion nanoparticles with higher sub-diffraction resolution
Author(s) -
Martin Plöschner,
Denitza Denkova,
Simone De Camillis,
Minakshi Das,
Lindsay M. Parker,
Xianlin Zheng,
Yiqing Lu,
Samuel Ojosnegros,
James A. Piper
Publication year - 2020
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.400651
Subject(s) - sted microscopy , optics , diffraction , materials science , stimulated emission , microscopy , biological imaging , resolution (logic) , image resolution , photon upconversion , spectral imaging , wavelength , laser , optoelectronics , fluorescence , physics , computer science , artificial intelligence
Upconversion nanoparticles (UCNPs) are becoming increasingly popular as biological markers as they offer photo-stable imaging in the near-infrared (NIR) biological transparency window. Imaging at NIR wavelengths benefits from low auto-fluorescence background and minimal photo-damage. However, as the diffraction limit increases with the wavelength, the imaging resolution deteriorates. To address this limitation, recently two independent approaches have been proposed for imaging UCNPs with sub-diffraction resolution, namely stimulated emission-depletion (STED) microscopy and super linear excitation-emission (uSEE) microscopy. Both methods are very sensitive to the UCNP composition and the imaging conditions, i.e. to the excitation and depletion power. Here, we demonstrate that the imaging conditions can be chosen in a way that activates both super-resolution regimes simultaneously when imaging NaYF 4 :Yb,Tm UCNPs. The combined uSEE-STED mode benefits from the advantages of both techniques, allowing for imaging with lateral resolution about six times better than the diffraction limit due to STED and simultaneous improvement of the axial resolution about twice over the diffraction limit due to uSEE. Conveniently, at certain imaging conditions, the uSEE-STED modality can achieve better resolution at four times lower laser power compared to STED mode, making the method appealing for biological applications. We illustrate this by imaging UCNPs functionalized by colominic acid in fixed neuronal phenotype cells.