Rational design of a negative photochromic spiropyran-containing fluorescent polymeric nanoprobe for sulfur dioxide derivative ratiometric detection and cell imaging

It is highly desirable to develop high-performance ratiometric fluorescent probes for SO2 derivative detection and realize their application in biological imaging. In this study, we report the rational design of a novel negative photochromic spiropyran derivative, spiro[azahomoadamantane-pyran] (MAHD-SP), with notable orange fluorescence in its stable ring-opened state without UV regulation. The unsaturated double bond of MAHD-SP underwent the Michael addition reaction of the SO2 derivative, making the fluorescence quenching of MAHD-SP obvious. Then, MAHD-SP, a fluorescent conjugated polymer PFO and a polymeric surfactant PEO113-b-PS49 were used to construct a ratiometric fluorescent polymeric nanoprobe (RFPN) via a coprecipitation method. The probe exhibited high sensitivity and selectivity for the ratiometric detection of SO2 derivatives in pure aqueous solutions. Moreover, the good biocompatibility of RFPN can be used to visualize exogenous and endogenous SO2 derivative generation in living cells.