Fluorescence imaging is a powerful tool for understanding fundamental processes in cellular biology. Materials used in imaging range from small organic molecules to proteins and nanoparticles (NPs). Polymeric nanoparticles with embedded dyes benefit from easy fabrication, high biocompatibility and design versatility. Light-emitting dyes integrated into the scaffolds by covalent attachment help to prevent dye leaching. A dual emissive iodide-substituted difluoroboron �-diketonate dye with covalently attached poly(lactic acid) (PLA), BF2b(I)bmPLA, has been being used for tumor hypoxia imaging. Both fluorescence (?F = 425 nm) and phosphorescence (?P = 525 nm) were exploited in ratiometric imaging. Recently a more redshifted naphthyl-substituted material, BF2n(Br)bmPLA, was prepared. Emission wavelengths (?F = 480 nm, ?P = 565 nm) are well aligned with the blue and green channels of a CCD camera for inexpensive and convenient imaging. By combining these two dyes via co-precipitation (i.e. one solution containing both polymers), energy transfer to and emission from the redshifted naphthyl dye is observed and the intensity of naphthyl dye phosphorescence relative to fluorescence increases. Though the dynamic range for oxygen sensing is only 0-3% for NPs made from BF2n(Br)bmPLA alone, when NPs were formed from the co-precipitation of BF2n(Br)bmPLA and BF2b(I)bmPLA, a 0-21% (i.e. air; ambient) oxygen range was observed. On the other hand, when these two dye-polymers are nanoprecipitated sequentially, one after another from separate solutions, core-shell materials may result. There is no evidence of energy transfer in this case. Instead, the observed optical properties are additive. The luminescence and oxygen sensing properties of the respective boron NPs and their admixtures fabricated in these different ways will be discussed. 

Energy transfer and oxygen sensing range modulation in luminescent boron �-diketonate-PLA hybrid nanoparticles

248th National Meeting (2014)

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