Real-time imaging and tracking of ultrastable organic dye nanoparticles in living cells

Semiconductor quantum dots and upconversion nanoparticles have been broadly used for live cell imaging due to their color tunability and photostability etc. However, these inorganic materials often contain heavy metals and potentially have metabolism problems. To overcome these issues, herein, we report a type of organic dye nanoparticles (NPs) with coating of a thin silica layer and folic acid targeting molecules on the surface for live cell imaging. These organic NPs possess superior characteristics of high fluorescence intensity, large Stokes shift, good photostability, emission in the NIR range, and targeted delivery, enabling them to be a powerful fluorescent probe for living cell imaging. In our study, we successfully demonstrate their applications in investigating cell division, exploring the cellular uptake kinetics and pathway of NPs, observing the distribution of NPs, and live-time tracking the trajectory of specific NPs. Considering the excellent properties and unique clathrin- and caveollae-independent intracellular uptake pathway, we expect that this type of organic dye NPs will play an important role in live cell imaging.