Time-gated luminescence probe for ratiometric and luminescence lifetime detection of Hypochorous acid in lysosomes of live cells.

Time-gated luminescence (TGL) probes based on lanthanide complexes have appealed wide attention in the detection of biologically relevant analytes because of their inimitable photophysical properties. In this work, a TGL probe (TR-HOCl) based on intramolecular Förster resonance energy transfer (FRET) system for specific determination of hypochlorous acid (HOCl) was designed and synthesized, in which a rhodamine derivative (energy acceptor) was conjugated to a luminescent Tb complex (energy donor). After reacting with HOCl, the Tb emission of TR-HOCl at 540 nm declined while the rhodamine emission at 580 nm increased, which leaded to an increase of the TGL intensity ratio of rhodamine to Tb complex (I/I) up to ~9-fold. The dose-dependent increase of I/I gives a nice linearity in HOCl concentration range of 0.5-45 μM. The detection limit of for HOCl was determined to be 0.34 μM. Interestingly, the average luminescence lifetime of the Tb emission decreased (from 588 μs to 254 μs) accompanied with the FRET process and the value gave a fine linearity to the variation of HOCl concentration. Additionally, TR-HOCl showed great selectivity for recognition of HOCl over other ROS, RNS, biothiols and other interference. These properties endow TR-HOCl to be conveniently applied for high accurate recognition of HOCl with ratiometric TGL and luminescence lifetime dual-signal output. Finally, TR-HOCl was successfully applied for the TGL determination of HOCl in HepG2 cells. The co-localization experiments of TR-HOCl with LysoSensor Green revealed the lysosome-localizing property of the probe in live cells. The study demonstrated that TR-HOCl could be a competent tool for investigating roles of HOCl in various physiological processes.