Aggregation-Induced Emission Luminogen-Embedded Silica
Nanoparticles Containing DNA Aptamers for Targeted Cell Imaging
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Abstract
Conventional
fluorophores usually undergo aggregation-caused quenching
(ACQ), which limits the loading amount of these fluorophores in nanoparticles
for bright fluorescence imaging. On the contrary, fluorophores with
aggregation-induced emission (AIE) characteristics are strongly fluorescent
in their aggregate states and have been an ideal platform for developing
highly fluorescent nanomaterials, such as fluorescent silica nanoparticles
(FSNPs). In this work, AIE luminogens based on salicylaldehyde hydrazones
were embedded in silica nanoparticles through a facile noncovalent
approach, which afforded AIE-FSNPs emitting much brighter fluorescence
than that of some commercial fluorescein-doped silica and polystyrene
nanoparticles. These AIE-FSNPs displaying multiple fluorescence colors
were fabricated by a general method, and they underwent much less
fluorescence variation due to environmental pH changes compared with
fluorescein-hybridized FSNPs. In addition, a DNA aptamer specific
to nucleolin was functionalized on the surface of AIE-FSNPs for targeted
cell imaging. Fluorescent microscopy and flow cytometry studies both
revealed highly selective fluorescence staining of MCF-7 (a cancer
cell line with nucleolin overexpression) over MCF-10A (normal) cells
by the aptamer-functionalized AIE-FSNPs. The fluorescence imaging
in different color channels was achieved using AIE-FSNPs containing
each of the AIE luminogens, as well as photoactivatable fluorescent
imaging of target cells by the caged AIE fluorophore