Triple-Emitting Dumbbell Fluorescent Nanoprobe for
Multicolor Detection and Imaging Applications
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Abstract
The
combination of different fluorescent species into one nanostructure
to develop fluorescent nanoparticles with multiple emission signatures
by a single wavelength excitation has become a very popular research
area in the field of multiplex bioanalysis, diagnostics, and multicolor
imaging. However, these novel hybrids must be elaborately designed
to ensure that the unique properties of each component are conveyed,
i.e., fluorescent species and nanoparticles, and are maximized without
serious interactions with each other. Herein, a first triple-fluorescence
dumbbell nanoprobe with large Stokes shift based on incorporating
fluorescein isothiocyanate (FITC) and lanthanide complexes onto Au–Fe<sub>3</sub>O<sub>4</sub> NPs was synthesized. This hybrid displays well-resolved
triple fluorescence emission, with FITC at 515 nm, Tb(III) complex
at 545 nm, and Eu(III) complex at 616 nm under a single-excitation
wavelength and is used for highly selective and sensitive colorimetric
detection of Cu<sup>2+</sup> with a detection limit of 30 nM. Under
different Cu<sup>2+</sup> concentrations, this hybrid exhibited distinguishable
multiple colors under UV light, and the color could change in the
presence of different concentrations of Cu<sup>2+</sup>. This sensor
for ratio/multianalyte microscopic imaging of Cu<sup>2+</sup> in HeLa
cells and BHK cells was also demonstrated. Target molecules, such
as folic acid, can be covalently attached to the fluorescent nanoparticle
surface to serve as an effective probe for simultaneous multicolor
imaging folate receptor-overexpressing HeLa cell lines in vitro