Fluorescent DNA Nanoprobes Decode Apoptotic Signals from Cytochrome c to Caspase-3

Apoptosis is a highly regulated process of programmed cell death crucial for maintaining homeostasis in multicellular organisms. The mitochondrial pathway is a central apoptotic route, where the release of cytochrome c (Cyt c) from mitochondria and subsequent activation of caspase-3 represent irreversible and pivotal events. Precise and dynamic detection of Cyt c and caspase-3 is, therefore, of paramount importance for fundamental biological research, investigation of disease mechanisms, and drug discovery. Conventional techniques, such as Western Blot, enzyme-linked immunosorbent assay, and flow cytometry, while widely used, require cell lysis, making them incapable of monitoring the dynamic processes of these key proteins in living cells in real-time, thereby losing critical spatiotemporal information. The emergence of fluorescent DNA nanoprobes has recently provided a revolutionary solution to this challenge. Leveraging the exceptional programmability, excellent biocompatibility, and precise molecular recognition capabilities of DNA molecules, these probes can be engineered to respond to Cyt c or caspase-3 with high specificity and sensitivity. Incorporated with signal transduction mechanisms like fluorescence resonance energy transfer (FRET), they enable the real-time, quantitative, and visualization of Cyt c release kinetics, caspase-3 activation, and even the signaling link between them within the live cell environment. This review systematically summarizes recent advances in fluorescent DNA nanoprobes for detecting apoptosis-related Cyt c and caspase-3, elaborates on their design principles, sensing mechanisms, and application advantages, and discusses current challenges and future perspectives.