Simultaneous imaging of intracellular pH and O2 using functionalized semiconducting polymer dots.

We developed novel functionalized semiconducting polymer dots (Pdots) for the simultaneous imaging of intracellular pH and oxygen. The Pdots comprised a semiconducting polymer of poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO), amino terminated polystyrene, fluorescein isothiocyanate (FITC) as a pH sensitive dye, and Pt(ii) meso-tetra(pentafluorophenyl)porphine (PtTFPP) as an oxygen sensitive dye. In the sensing Pdots, PFO was used as a donor for Förster resonance energy transfer. The emission wavelengths of the PFO, FITC and PtTFPP matched the three color channel of the red, green and blue chip, which offered great advantage for dual sensing using conventional fluorescence microscopy. The nanosensor was taken up by cells via endocytosis, and exhibited high brightness, small particle size, triple color under a single excitation, a large two-photon absorbance cross-section and low-toxicity to cells. These salient features demonstrated the potential utility of the Pdots for dual pH and O2 imaging in cells.