Two-Photon Semiconducting Polymer Dots with Dual-Emission for Ratiometric Fluorescent Sensing and Bioimaging of Tyrosinase Activity.

Semiconducting polymer dots (Pdots) with one-, two-photon excitation and dual-emission have been synthesized by coprecipitation of two conjugated polymers including poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovinylene-1,4-phenylene)] (CN-PPV) and have been further functionalized with l-tyrosine methyl ester (Tyr-OMe) via electrostatic assembly for ratiometric fluorescent sensing and bioimaging of tyrosinase activity. Tyrosinase-catalyzed oxidation of Tyr-OMe effectively modulate the dual-emission fluorescence of PFO/CN-PPV@Tyr-OMe Pdots from orange to blue through a selective photoinduced electron transfer (PET) process. A two-photon ratiometric sensor at almost zero-background interference and bioimaging of tyrosinase activity have been demonstrated, suggesting the potential biomedical applications of the prepared functionalized Pdots.