Membrane‐Targetable Probes for Hg 2+ Detection in Live Cells and Paper‐Based Devices

Two novel fluorogenic probes ( HGMem‐2 and −3 ) for detecting Hg 2+ were designed, synthesized and characterized. Probes based on a commercially available fluorophore (fluorescein) with high brightness were equipped with/without a photolabile group (2‐nitrobenzyl group), a membrane‐anchoring unit (cholesterol) and a Hg 2+ ‐reactive moiety. Taking advantage of the hydrophobicity of the cholesterol group in the probe, a paper‐based device spotted with HGMem‐2 was developed as a Hg 2+ paper indicators, and showed feasibility in complex cell lysate. Only upon UV photolysis, HGMem‐3 displayed more than 1900‐fold fluorescence enhancement with the addition of Hg 2+ . Furthermore, they exhibited pronounced Hg 2+ ‐selective fluorogenic signalling behavior over other 45 analytes. Importantly, HGMem‐3 was utilized to specifically visualize Hg 2+ near cell membrane in live HepG2 cells with high spatiotemporal resolution, avoiding the influence of reactive species outside cells successfully. Hence, our newly developed membrane‐anchored Hg 2+ sensors provide useful tools for versatile applications in biological and environmental research.