Stable red nanoparticles loaded neutral luminescent radicals for fluorescence imaging

Although neutral luminescent radicals have arisen much attention recently, their applications in fluorescence imaging are rarely reported due to their insolubility in water and weak luminescence in polar solvents. Herein, we encapsulated a luminescent radical and its precursor into nanoparticles (NPs) by an amphiphilic polymer matrix, DSPE-PEG2000, to avoid aggregation-caused quenching and poor solubility in water to further achieve its application in cell-imaging. The obtained radical NPs exhibited strong red emission, excellent stability and remarkable biocompatibility under physiological conditions. The radical NPs were incubated with live HCT116 cells and showed good cellular uptake, thus making fluorescence imaging possible in vitro. The results confirm the feasibility of stable neutral luminescent radical as a promising candidate for the application in fluorescence imaging.