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.