Simultaneously targeted imaging cytoplasm and nucleus in living cell by biomolecules capped ultra-small GdOF nanocrystals

Simultaneously targeted imaging cytoplasm and nucleus in living cell by just one photoluminescent nanocrystals has been a giant challenge in nanobiotechnology and nanomedicine. Herein we report a novel Arg-Gly-Asp peptide (RGD) or cysteine (Cys) functionalized ultra-small GdOF nanocrystals for simultaneously targeted imaging cell cytoplasm and nucleus. As-prepared RGD@GdOF and Cys@GdOF nanocrystals possessed high water dispersibility, ultra-small size (about 5 nm) and double emissions (545 nm and 587 nm) with high quantum yield. Such functionalized nanocrystals presented high cellular biocompatibility and were successfully used to label living cells with very high signal to noise ratio. The living cells cytoplasm and nucleus (cancer cells and stem cells) could be imaged simultaneously through the mergence of green and red emission of nanocrystals, based on mechanism of fluorescent intensity difference. These functionalized nanocrystals also exhibited significantly higher photostability and brightness as compared to dyes. Such the ultra-small size, high photostability and intensity, double emissions, excellent biocompatibility and targeted ability, make as-prepared functionalized nanocrystals particularly promising for cellular and molecular-level bioimaging applications.