UV-enhanced oxidative quenching of PFO–PFPV Pdots for ratiometric quantification and imaging of hypochlorous acid in living cells

It is imperative to develop methods for quantifying and imaging hypochlorous acid/hypochlorite (HOCl/ClO−) in living systems to clarify its roles in physiological and pathological processes and optimize therapeutic interventions for related diseases. Herein, we develop a ratiometric semiconducting polymer dot (Pdot)-based fluorescent probe with dual-emission at blue and green regions, PFO–PFPV Pdot, which is prepared from two fluorescent conjugated polymers including poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) and poly[(9,9-dioctyl-2,7-divinylene-fluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] (PFPV), for detecting and imaging HOCl in living cells. The presence of HOCl can selectively oxidize PFPV components in Pdots and the oxidation reaction can be enhanced by UV irradiation, which interrupts the fluorescence resonance energy transfer (FRET) from PFO to PFPV and results in the fluorescence quenching of PFPV at green emission region and recovery of PFO at blue emission region. On the basis of the ratios of fluorescence intensities at PFPV and PFO as a function of HOCl concentrations, a ratiometric fluorimetry for HOCl detection with a low detection limit of 56.8 nM is proposed. Furthermore, the developed fluorescent probe is also used for ratiometric fluorescence imaging of exogenous and endogenous HOCl in RAW264.7 cells with satisfactory results. The developed PFO–PFPV Pdots show high specificity and sensitivity, low cytotoxicity, and good biocompatibility for HOCl detection.