Dye sensitized luminescent europium nanoparticles and its time-resolved fluorometric assay for DNA

The preparation and detection of highly luminescent aqueous europium nanoparticle labels for the time-resolved fluorometric assays has been demonstrated. The luminescent complexes included in the nanoparticle were composed of a dye sensitizer and a polyaminocarboxylate-based chelator with excellent water-solubility and a high binding constant for lanthanides. The luminescence of europium is greatly enhanced by the sensitization of the dye. The structure design of two functional entities in the single molecule made the lanthanide complex to have both strong luminescence and good aqueous solubility. SiO2 nanoparticles containing europium complexes were prepared by the reverse microemulsion method. One particle of ∼55 nm in diameter has a luminescent intensity corresponding ∼1300 free europium complexes and 0.61 ms fluorescence lifetime. The DNA time-resolved fluorometric assay with this nanoparticle label was carried out by magnetic microbeads as solid phase carrier. The detection sensitivity with the nanoparticles is improved more than 50-fold compared with the conventional dye FITC molecules. This luminescent nanoparticle label based on dye sensitization can be applied in ultrasensitive time-resolved fluorometric assays and imaging.