Development of a novel lysosome-targetable time-gated luminescence probe for ratiometric and luminescence lifetime detection of nitric oxide .

Rapid, multiplexed, sensitive and specific identification and quantitative detection of nitric oxide (NO) are in great demand in biomedical science. Herein, a novel multifunctional probe based on the intramolecular LRET (luminescence resonance energy transfer) strategy, , was designed for the highly sensitive and selective ratiometric and luminescence lifetime detection of lysosomal NO. Before reaction with NO, the emission of the rhodamine moiety in is switched off, which prevents the LRET process, so that the probe emits only the long-lived Tb luminescence. However, upon reaction with NO, accompanied by the turn-on of rhodamine emission, the LRET from the Tb-complex moiety to rhodamine moiety occurs, which results in a remarkable increase of the rhodamine emission and decrease of the Tb emission. After the reaction, the intensity ratio of the rhodamine emission to the Tb emission, /, was found to be 28.8-fold increased, and the dose-dependent enhancement of the / value showed a good linearity upon the increase of NO concentration. In addition, a dose-dependent luminescence lifetime decrease was distinctly observed between the average luminescence lifetime of the probe and NO concentration, which provides a ∼10-fold contrast window for the detection of NO. These unique properties allowed to be conveniently used as a time-gated luminescence probe for the quantitative detection of NO using both luminescence intensity ratio and luminescence lifetime as signals. The applicability of for ratiometric time-gated luminescence imaging of NO in living cells was investigated. Meanwhile, dye co-localization studies confirmed a quite precise distribution of in lysosomes by confocal microscopy imaging. Furthermore, the practical applicability of was demonstrated by the visualization of NO in . All of the results demonstrated that could serve as a useful tool for exploiting and elucidating the function of NO at sub-cellular levels with high specificity, accuracy and contrast.