Fluorescent/Phosphorescent Dual-Emissive Probe for Simultaneous and Independent Sensing of Intracellular Hypochlorite and pH via Time-Resolved Luminescence Imaging

Abstract

In this work, we present a dual-emissive polymeric probe capable of simultaneous and independent sensing of intracellular hypochlorite and pH. The probe integrates an anthracene–carboxamide-based fluorescent compound with a phosphorescent iridium(III) complex. The fluorescence and phosphorescence spectra are significantly overlapped at 500 to 650 nm, but their lifetimes differ substantially at 14.8 and 1113.6 ns, respectively, thereby allowing for monitoring in different time intervals through time-resolved luminescence analysis. The fluorescence is quenched upon oxidation by hypochlorite, whereas an acidic environment favors protonation of pyridyl groups on the iridium(III) complex, which causes phosphorescence quenching. During hypochlorite sensing, a linear plot of the fluorescence/phosphorescence ratio over hypochlorite concentration was obtained. During pH sensing, the pK_a value was calculated to be about 4.6. The utilization of this probe for imaging cellular endogenous hypochlorite and intracellular pH values was demonstrated. The short-lived and long-lived signals were successfully extracted via time-resolved luminescence imaging microscopy, thereby allowing independent, simultaneous, and quantitative analysis of fluorescence and phosphorescence signals and their response toward hypochlorite and pH values. This study offers potential implications for the development of biosensing and bioimaging applications and paves the way for the simultaneous multiplexed detection of physiological and pathological activities within living cells.