Quaternary ammonium salt-functionalized fluorescent probes: Integrating the functions of cysteine detection,...

Abnormal cysteine (Cys) levels are implicated in the pathogenesis of cardiovascular diseases and metabolic disorders, with mitochondrial Cys perturbation being a critical indicator of redox imbalance and disease risk. Fluorescent probes have emerged as a key method for detecting Cys and a research hotspot in recent years. Current development trends are increasingly focusing on enhancing aqueous solubility and achieving multifunctionality. Herein, we report a series of cationic fluorescent probes engineered by integrating a quaternary ammonium-functionalized phthalimide fluorophore with a 2,4-dinitrofluorobenzene recognition moiety. Among these probes, CBTA exhibited high sensitivity and selectivity toward Cys, achieving a limit of detection of 2.25 × 10^-7 M. Its practical utility was validated in real sample analyses, which yielded recovery rates of 94 %-110 % and confirmed its specificity. Mitochondrial colocalization experiments confirmed that CBTA exhibited effective mitochondrial targeting capability, with a Pearson's correlation coefficient of 0.79. All these quaternized probes demonstrated significant antibacterial activity, with NDTA achieving a remarkable 100 % inhibition rate. This study presents an integrated platform that synergistically combines fluorescent sensing, targeted imaging, and antibacterial functionality, holding potential applications in fluorescence detection and disease diagnosis and treatment.