Multi-photon super-linear image scanning microscopy using upconversion nanoparticles

• Published in: arXiv.org 2024-03
• Main Authors: Wang, Yao, Liu, Baolei, Ding, Lei, Chen, Chaohao, Shan, Xuchen, Wang, Dajing, Tian, Menghan, Song, Jiaqi, Zheng, Ze, Xu, Xiaoxue, Zhong, Xiaolan, Wang, Fan
• Format: Article
• Language: English
• Subjects: Continuous radiation; Excitation; Image enhancement; Image resolution; Infrared lasers; Microscopy; Nanoparticles; Photons; Scanning microscopy; Second harmonic generation; Upconversion
• ISSN: 2331-8422

Super-resolution fluorescence microscopy is of great interest in life science studies for visualizing subcellular structures at the nanometer scale. Among various kinds of super-resolution approaches, image scanning microscopy (ISM) offers a doubled resolution enhancement in a simple and straightforward manner, based on the commonly used confocal microscopes. ISM is also suitable to be integrated with multi-photon microscopy techniques, such as two-photon excitation and second-harmonic generation imaging, for deep tissue imaging, but it remains the twofold limited resolution enhancement and requires expensive femtosecond lasers. Here, we present and experimentally demonstrate the super-linear ISM (SL-ISM) to push the resolution enhancement beyond the factor of two, with a single low-power, continuous-wave, and near-infrared laser, by harnessing the emission nonlinearity within the multiphoton excitation process of lanthanide-doped upconversion nanoparticles (UCNPs). Based on a modified confocal microscope, we achieve a resolution of about 120 nm, 1/8th of the excitation wavelength. Furthermore, we demonstrate a parallel detection strategy of SL-ISM with the multifocal structured excitation pattern, to speed up the acquisition frame rate. This method suggests a new perspective for super-resolution imaging or sensing, multi-photon imaging, and deep-tissue imaging with simple, low-cost, and straightforward implementations.