A visible-light-excited Eu³⁺ complex-based luminescent probe for highly sensitive time-gated luminescence imaging...

Although considerable efforts have been made for the development of lanthanide complex-based luminescent probes, a major drawback of the current probes is the requirement for UV excitation. In this work, a visible-light-excited Eu³⁺ complex-based luminescent probe, [Eu(HDPH)₃(DPBT)] (HDPH: 1,1,1,2,2,3,3-heptafluoro-6-(2,4-dimethoxyphenyl)-4,6-hexanedione; DPBT: 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine), has been designed and synthesized for the highly sensitive and selective time-gated luminescence imaging detection of peroxynitrite (ONOO^-) in living cells. The probe exhibits a strong visible excitation peak at 400 nm, with the excitation window extending to beyond 460 nm. Upon reaction with ONOO^-, the luminescence of the probe at 610 nm is greatly quenched because the excited state of the Eu³⁺ complex is deactivated by the interaction between the 2,4-dimethoxyphenyl moiety and ONOO^-. The dose-dependent luminescence decrease of the probe shows good linearity with a detection limit of 1.8 μM for ONOO^-, and the probe can specifically distinguish ONOO^- from other reactive oxygen/nitrogen species (ROS/RNS). The [Eu(HDPH)₃(DPBT)]-loaded HepG2 cells were prepared, and then the exogenous ONOO^- in HepG2 cells was successfully imaged in time-gated luminescence mode. The photostability results of the [Eu(HDPH)₃(DPBT)]-loaded HepG2 cells demonstrate the practical applicability of the visible-light-excited probes for long-term cell imaging.