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We combined the unique natural oxygen transporting function of red blood cells (RBCs) with photosensitive nanocomposites to create biomaterials with strong singlet oxygen (1O 2) generation. During cold storage for a long time, structural changes to RBCs may occur, which reduce their oxygen carrying capacity. The nanocomposite developed herein featured dual emission characteristic, which enabled evaluation of the status of the RBCs. On the basis of energy transfer from the conjugated polymer to iridium(III) complexes, the formed nanocomposites show intense, long-lived and oxygen-sensitive emission. When modified with 1,2-distearoyl- sn -glycero-3-phosphoethanolamine- N -[methoxy(polyethyleneglycol)-2000], the nanocomposites non-invasively entered RBCs through hydrophobic interactions. We measured the quenching effect of oxygen on the emission of the iridium(III) complexes. The differential fluorescent signals and fluorescence lifetime images indicated the storage history of the RBCs. RBCs in good condition stored oxygen. When engineered with nanocomposites, RBCs generated large amounts of cytotoxic 1O 2 upon irradiation. These decorated RBCs might serve as a new kind of photosensitive biomaterial. Image 1 • The nanocomposites show intense dual-emission based on efficient energy transfer. • The nanocomposites possess oxygen-sensitive luminescence properties. • The oxygen-carrying ability of stored RBCs can be analyzed by the nanocomposites. • The oxygen supply in modified RBCs generated vast cytotoxic 1O 2 upon irradiation. [ABSTRACT FROM AUTHOR]

Abstract The mixing of donor and acceptor molecules in fluorescent nanoparticles offers an effective route to adjusting the emission properties of the nanoparticles. In this work, the electron donor 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and the electron acceptor 2,4-bis[4-(diphenylphosphinyl)phenyl]-6-[4-(hexyloxy)phenyl]-1,3,5-triazine (BPOTZ-OR) were coprecipitated to form fluorescent nanoparticles. Efficient exciplex emission occurred in the nanoparticles owing to the good electron affinity and appropriate stacking distance between TAPC and BPOTZ-OR. The exciplex emission and monomer emission were easily tuned by simply changing the BPOTZ-OR/TAPC molar ratio. An appropriate combination produced white-light emission. The large red-shift of the emission from the exciplex, good stability under physiological conditions, and low toxicity suggest potential for this kind of nanoparticle to be an effective fluorescent probe for cell imaging. Graphical abstract Image 1 Highlights • Exciplex emission nanoparticles upon appropriate stacking distance were prepared. • Multicolor emission can be obtained by adjusting the donor-acceptor molar ratio. • The exciplex nanoparticles showed excellent performance in live cell imaging. [ABSTRACT FROM AUTHOR]