A Targeted and FRET- Based Ratiometric Fluorescent Nanoprobe for Imaging Mitochondrial Hydrogen Peroxide in Living Cells

Hydrogen peroxide (H2O2) is a prominent member of the reactive oxygen species family and plays crucial roles in living organisms, thus detecting H2O2 and elucidating its biological functions has become an important area of biological and biomedical research. Herein, a multifunctional fluorescent nanoprobe is demonstrated for detecting mitochondrial H2O2. The nanoprobe is prepared by covalently linking a mitochondria-targeting ligand (triphenylphosphonium, TPP) and a H2O2 recognition element (PFl) onto carbon dots (CDs). For this nanoprobe, the CD serves as the carrier and the FRET donor. In the presence of H2O2, the PFl moieties on a CD undergo structural and spectral conversion, affording the nanoplatform a FRET-based ratiometric probe for H2O2. The nanoprobe displays excellent water dispersibility, high sensitivity and selectivity, satisfactory cell permeability, and very low cytotoxicity. Following the living cell uptake, this nanoprobe can specifically target and stain the mitochondria; and it can detect the exogenous H2O2 in L929 cells, as well as the endogenously produced mitochondrial H2O2 in Raw 264.7 cells upon stimulation by PMA. This study shows that CDs can serve as promising nano-carriers for fabricating practical multifunctional fluorescent nanosensors.