SiQDs-(K/L-P)ox Fluorescent Probe: Mitochondria Targeting for ONOO- Imaging in HepG2 Cells

The targeting ability of SiQDs-(K/L-P)ox fluorescent probe was investigated through a colocalization experiment. Figure 5b presents fluorescence micrographs of HepG2 cells incubated with 50 μg/mL SiQDs-(K/L-P)ox and organelle-specific fluorescent dyes, including mitochondrial, lysosomal, and nuclear staining. The overlapping image of the probe and Mito Tracker Red displayed a high correlation with a Pearson coefficient of 0.99. Additionally, the intensity of the cells in the red and yellow channels was closely synchronized, as seen in the fluorescence image. The colocalization images of the probe with Lyso Tracker Red demonstrated that the 514 nm channel overlapped well with the 552 nm channel, and the fluorescence intensity image showed high uniformity with a Pearson coefficient of 0.78.

However, the fluorescence intensities of Hoechst 33342 and SiQDs-(K/L-P)ox barely overlapped in the selected region, and the Pearson coefficient was only 0.59. This indicates that the probe cannot be localized in the nucleus. Since mitochondria are the primary site for the formation and reaction of ONOO- in living cells, SiQDs-(K/L-P)ox is suitable for imaging ONOO- in living cells.