A ratiometric time-gated luminescence probe for hydrogen sulfide based on copper(II)-coupled lanthanide complexes

Time-gated luminescence (TGL) bioassay technique using luminescent lanthanide complexes as probes has exhibited excellent practicability in detection of various analytes in autofluorescence-rich biosamples. Herein, a novel copper(II)-coupled lanthanide complex-based luminescence probe has been developed for the ratiometric TGL detection of hydrogen sulfide (H₂S) in vitro and in vivo. The probe is constructed based on a dual-functional ligand that was synthesized by conjugating di(2-picolyl)amine with terpyridine polyacid (DATP) using the "click chemistry" method. The as-prepared ligand can coordinate to Eu³⁺ and Tb³⁺ ions with its terpyridine polyacid moiety to display long-lived emissions of Eu³⁺ and Tb³⁺ ions, while the further coordination of its di(2-picolyl)amino moiety to Cu²⁺ induces to the luminescence quenching of the Eu³⁺ complexes, which allows the probe consisting of the heterometallic Cu²⁺-DATP-Eu³⁺/Tb³⁺ complexes to be constructed. After the probe was reacted with H₂S to lead to the release of Cu²⁺ from the complexes, the emission of Eu³⁺ at 610 nm was remarkably enhanced, while that of Tb³⁺ at 540 nm was changed slightly. This luminescence response feature allowed the probe to be conveniently applied for the ratiometric TGL determination of H₂S with I₆₁₀/I₅₄₀ as the signal. The applicability of the probe for quantitative detection of H₂S in human sera as well as for imaging of H₂S in living cells and zebrafish were evaluated. All of the results proved the potential of the probe for in vitro and in vivo applications.