A Thiophilic Hg²⁺-Activated Fluorescent Probe for Multiscale Bioimaging: From Living Cells and Mice to Tomato Plants

Mercury ions (Hg²⁺) have been demonstrated to disrupt key physiological and biochemical processes in plants, and therefore, early detection and real-time monitoring of Hg²⁺ concentration dynamics in plants, particularly in crops, are of critical importance. Currently, very few reported fluorescent probes have been applied for Hg²⁺ detection in crops, and in-depth investigations into Hg²⁺ accumulation behavior in plants remain scarce. To address this gap, we developed a novel "Turn-On" Hg²⁺-activated molecular probe, LBR, and systematically evaluated its performance. The probe exhibited high sensitivity and selectivity in vitro and was successfully applied to rapid, real-time fluorescence imaging of Hg²⁺ in HeLa cells. At the in vivo level, the probe further enabled noninvasive, real-time detection of Hg²⁺ in mouse models. More importantly, owing to its excellent tissue permeability and minimal susceptibility to chlorophyll interference, the probe was successfully employed for in situ, multiscale visual monitoring of Hg²⁺ dynamics in tomato plants: at the tissue level, it achieved Hg²⁺ imaging in root and stem sections; at the organ level, it accomplished Hg²⁺ distribution tracing in whole roots and entire plants. The study confirmed that under Hg²⁺ exposure, the accumulation of Hg²⁺ in plant tissues increases with both exposure duration and concentration. In summary, this work not only provides an efficient fluorescent probe for Hg²⁺ but also establishes a multiscale detection system spanning cells, animals, and living plants. It offers a robust methodological tool for further investigating the distribution, accumulation, and transport mechanisms of Hg²⁺ in plant systems.