Recent advances in the design mechanisms of mitochondrial fluorescent probes: A review

Mitochondria are central regulators of cellular energy metabolism, redox balance, and signal transduction, and fluorescent probes have become indispensable tools for visualizing their structure and function with high spatial and temporal precision. Because mitochondrial physiological parameters, including membrane potential, pH, viscosity, reactive species, and ion fluxes, arise from distinct microenvironmental features, their accurate detection requires probe designs based on different photophysical mechanisms. Although several reviews have summarized probes for specific mitochondrial indicators, systematic discussions focused on the underlying photophysical design mechanisms remain scarce. In this review, we comprehensively summarize the major mechanisms that govern mitochondrial probe performance, including photoinduced electron transfer (PET), intramolecular charge transfer (ICT), Förster resonance energy transfer (FRET), aggregation-induced emission (AIE), and excited-state intramolecular proton transfer (ESIPT). Particular emphasis is placed on their design principles, analytical characteristics, representative applications, and inherent advantages and limitations from a bioanalytical perspective. It is respected that this mechanism-oriented review will provide useful guidance for the rational development of next-generation mitochondrial fluorescent probes for precise imaging and sensing.