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In this study, fluorescence-encoded magnetic biocompatible nanoparticles (NPs) were constructed from CdSe@ZnS quantum dots (QDs) and Fe3O4 nanoparticles with a one-step reprecipitation-encapsulation method. The resultant hybrid NPs exhibit small size (∼130 nm in diameter), highly bright QDs, two-color emissions (green and red) under single-wavelength excitation, easy separation with a magnet and efficient cellular internalization. Energy transfer between the incorporated QDs was studied to better tailor the encoded fluorescence, and 11 barcodes were obtained by adjusting the ratio of green and red QDs. We used four sets of the barcodes to tag specific cancer cells (HepG2) as a proof-of-concept, and distinguished each set according to respective overlayed fluorescence images using laser confocal microscopy. Moreover, the incorporated Fe3O4 NPs endowed as-constructed optical barcode superparamagnetic property by T2-enhanced magnetic resonance effect with an r2 value of 145.25 s−1 mM−1 at 3 T. These results suggest that the multifunctional NPs are very promising for discriminating different cells and dual-modality imaging. [ABSTRACT FROM AUTHOR]

Singlet oxygen (1O2) detection remains an active area of research in the field of biological and biomedical science. In this work, we reported a novel Off‐On type FRET‐based fluorescent 1O2 nanoprobe comprising the energy‐donating conjugated polymer, poly(9,9‐dioctylfluorenyl‐2,7‐diyl) (PFO), and the energy‐accepting 1O2 indicator, 3‐diphenylisobenzofuran (DPBF). Prior to the reaction with 1O2, the nanoprobe was in Off‐state because fluorescence of PFO (λem=441 nm) was completely quenched by loaded DPBF; in the presence of 1O2, it switched to On‐state due to the depletion of DPBF. The as‐prepared 1O2 nanoprobe had a particle size of ∼59 nm, good biocompatibility, high specificity and sensitivity with a limit of detection of 353 nM. Importantly, the fluorescent nanoprobes were highly sensitive to 1O2 under two‐photon excitation (λex=800 nm). Using a multiphoton confocal microscope, generation of intracellular 1O2 during photodynamic therapy was sensitively detected by recording fluorescence intensity of the nanoprobes. [ABSTRACT FROM AUTHOR]