Ultra-photostable, non-cytotoxic, and highly fluorescent quantum nanospheres for long-term, high-specificity cell imaging

A new class of fluorescent quantum nanospheres (QNs) is directly achieved in aqueous phase through a facile one-pot microwave irradiation (MWI) strategy. Multi-color QNs with maximum emission wavelengths ranging from 525 to 610 nm and PLQY of 30-60% are facilely prepared through this new MWI strategy. In addition to strong fluorescence, these QNs possess excellent photostability, preserving ∼90% of the original intensity after 70 min high-power UV irradiation (100 W Xeon lamp). In sharp contrast, the fluorescence of CdTe/CdS/ZnS core-shell-shell quantum dots (QDs), recognized as established fluorescent probes with robust photostability, decrease to ∼50% under the same conditions. Besides, cytotoxicity assessment demonstrates that the prepared QNs exhibit favorable cytocompatibility to K562 cells with high concentration (3 μmol) and long-time incubation (24 h). Furthermore, cellular imaging results demonstrate that the as-prepared QNs are remarkably efficacious for long-term and high-specificity immunofluorescent cellular labeling, and multi-color cell imaging. Our systematical investigation clearly shows that these high-performance QNs may serve as practical and powerful tools for various biological researches, such as in vivo and in vitro imaging.