Mitochondria–Nucleus\nMigration Probe for Ultrasensitive\nMonitoring of mtDNA Damage in Living Cells

Mitochondrial\nDNA (mtDNA) damage is a prevalent phenomenon that\nhas been proven to be implicated in a wide spectrum of diseases. However,\nthe progressive attenuation of probe signals in response to mtDNA\ndamage within living cells inherently limits the sensitivity and precision\nof current probes for detecting mtDNA damage. Herein, we employ an\ninnovative organelle signal ratio imaging approach, utilizing the\nmitochondria–nucleus migration probe MCQ, to achieve unparalleled\nsensitivity in detecting mtDNA damage in living cells. MCQ exhibited\nan initial preferential binding to mtDNA, facilitated by its cationic\nquinolinium moiety, but migrated to the nucleus upon mtDNA damage.\nThis unique migration behavior not only enhanced the spatial identifiability\nof mtDNA damage but also amplified detection sensitivity and precision\nsignificantly by harnessing the intensified nucleus signal against\nthe attenuated mitochondrial signal. This innovative approach established\na positive correlation between the signal and mtDNA damage, enabling\nthe detection of even subtle mtDNA damage at the early stage of apoptosis\nwith a remarkable 23-fold enhancement following just 5 min H<sub>2</sub>O<sub>2</sub> induction in living cells, whereas conventional methods\nrelying solely on the fading of mitochondrial signals proved insufficient.\nFurthermore, MCQ’s ability to monitor the occurrence of mtDNA\ndamage achieved the intricate differentiation between apoptosis and\nferroptosis. By monitoring mtDNA damage, drug-induced apoptosis in\ncancer cells was further conducted using MCQ to evaluate the therapeutic\nefficacy of four anticancer drugs at very low concentrations. This\ninnovative strategy not only paves the way for ultrasensitive detection\nof mtDNA damage but also holds immense promise for early monitoring\nof mtDNA damage-associated diseases.