Lanthanide-doped upconversion nanoparticles for biological super-resolution fluorescence imaging

Super-resolution fluorescence microscopy is a powerful, non-invasive tool to visualize subcellular structures and probe the dynamics of biomolecules in real time. Owing to their properties of stable multicolor emissions, large anti-Stokes shifts, tunable luminescence lifetimes, and good biocompatibility, lanthanide-doped upconversion nanoparticles (UCNPs) have gained popularity as fluorescent probes for super-resolution microscopy. In this review, we summarize the optical and biological properties of UCNPs and their applications in super-resolution fluorescence microscopy. By comparing the imaging performance of the latest strategies, we highlight that continuing efforts should focus on manipulating upconversion emissions, synthesizing smaller particles with bright luminescence, and integrating UCNPs with different imaging modes to meet the requirements of biological super-resolution imaging.