AIE Nanoparticles with High Stimulated Emission Depletion Efficiency and Photobleaching Resistance for Long-Term Super-Resolution Bioimaging

Stimulated emission depletion (STED) nanoscopy is a typical super-resolution imaging technique that has become a powerful tool for visualizing intracellular structures on the nanometer scale. Aggregation-induced emission (AIE) luminogens are ideal fluorescent agents for bioimaging. Herein, long-term super-resolution fluorescence imaging of cancer cells, based on STED nanoscopy assisted by AIE nanoparticles (NPs) is realized. 2,3-Bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenyl)amino)phenyl) fumaronitrile (TTF), a typical AIE luminogen, is doped into colloidal mesoporous silica to form fluorescent NPs. TTF@SiO₂ NPs bear three significant features, which are all essential for STED nanoscopy. First, their STED efficiency can reach more than 60%. Second, they are highly resistant to photobleaching, even under long-term and high-power STED light irradiation. Third, they have a large Stokes' shift of ≈150 nm, which is beneficial for restraining the fluorescence background induced by the STED light irradiation. STED nanoscopy imaging of TTF@SiO₂ -NPs-stained HeLa cells is performed, exhibiting a high lateral spatial resolution of 30 nm. More importantly, long-term (more than half an hour) super-resolution cell imaging is achieved with low fluorescence loss. Considering that AIE luminogens are widely used for organelle targeting, cellular mapping, and tracing, AIE-NPs-based STED nanoscopy holds great potential for many basic biomedical studies that require super-resolution and long-term imaging.