Mitochondria–Nucleus Migration Probe for Ultrasensitive Monitoring of mtDNA Damage in Living Cells

Mitochondrial DNA (mtDNA) damage is a prevalent phenomenon that has been proven to be implicated in a wide spectrum of diseases. However, the progressive attenuation of probe signals in response to mtDNA damage within living cells inherently limits the sensitivity and precision of current probes for detecting mtDNA damage. Herein, we employ an innovative organelle signal ratio imaging approach, utilizing the mitochondria-nucleus migration probe MCQ, to achieve unparalleled sensitivity in detecting mtDNA damage in living cells. MCQ exhibited an initial preferential binding to mtDNA, facilitated by its cationic quinolinium moiety, but migrated to the nucleus upon mtDNA damage. This unique migration behavior not only enhanced the spatial identifiability of mtDNA damage but also amplified detection sensitivity and precision significantly by harnessing the intensified nucleus signal against the attenuated mitochondrial signal. This innovative approach established a positive correlation between the signal and mtDNA damage, enabling the detection of even subtle mtDNA damage at the early stage of apoptosis with a remarkable 23-fold enhancement following just 5 min H₂O₂ induction in living cells, whereas conventional methods relying solely on the fading of mitochondrial signals proved insufficient. Furthermore, MCQ's ability to monitor the occurrence of mtDNA damage achieved the intricate differentiation between apoptosis and ferroptosis. By monitoring mtDNA damage, drug-induced apoptosis in cancer cells was further conducted using MCQ to evaluate the therapeutic efficacy of four anticancer drugs at very low concentrations. This innovative strategy not only paves the way for ultrasensitive detection of mtDNA damage but also holds immense promise for early monitoring of mtDNA damage-associated diseases.