General Strategy to Achieve Color-Tunable Ratiometric Two-Photon Integrated Single Semiconducting Polymer Dot for Imaging Hypochlorous Acid

It is highly desired and challenging to construct integrated (all-in-one) single semiconducting-polymer-derived dot (Pdot) without any postmodification but with desired performances for bioapplications. In this work, eight hypochlorous acid (HClO)-sensitive integrated polymers and corresponding polymer-derived Pdots are designed through molecular engineering to comparatively study their analytical performances for detecting and imaging HClO. The optimized polymers-derived Pdots are obtained through regulating donor-acceptor structure, the content of HClO-sensitive units, and the position of HClO-sensitive units in the polymer backbone. The designed Pdots display distinguished characteristics including multicolours with blue, yellow, and red three primary fluorescence colors, determination mode from single-channel to dual-channel (ratiometric) quantification, ultrafast response, low detection limit, and high selectivity for ClO- sensing based on specific oxidation of ClO--sensitive unit 10-methylphenothiazine (PT) accompanied by altering the intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) processes in Pdots. The prepared integrated Pdots are also applied for two-photon ClO- imaging in HeLa cells and one- and two-photon ClO- imaging produced in acute inflammation in mice with satisfactory results. We believe that the present study not only provides excellent integrated fluorescent nanoprobes for ClO- monitoring in living systems but also extends a general strategy for designing integrated semiconducting polymers and Pdots with desired performances for biological applications.