Magnetic Fluorescent Nanoparticles Binding to Amyloid-Beta Peptide: Silica-Coated, Thioflavin-T Functionalized Iron Oxide

Formation and accumulation of extracellular amyloid-beta (
$\text{A}\beta )$
peptide aggregates in the brain are associated with Alzheimer’s disease, a widespread age-related form of dementia, for which there is no effective treatment at present. It is essential to discover ways of visualizing and monitoring the progress of aggregation toward amyloidic plaques while at the same time therapeutic methods inhibiting the aggregation can be explored. Iron oxide nanoparticles Fe
₃
O
₄
with size ~10 nm have been coated with silica SiO
₂
and Thioflavin-T (ThT), a non-toxic fluorescent dye binding to the amyloid-
$\beta $
structures with a possible effect on fibril formation, and then added to
$\text{A}\beta _{\mathrm {1-42}}$
phosphate-buffered saline solution, incubated for 30 min and extracted by magnetic separation. The magnetic ThT silica-coated nanoparticles with size ~20 nm have been characterized structurally and magnetically by powder X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and vibrating sample magnetometer. Their affinity to
$\text{A}\beta _{\mathrm {1-42}}$
peptide, examined by fluorescence microscopy and protein concentration measurements using the BCA Protein Assay Kit has been verified. Successful binding of magnetic silica nanoparticles, doped with ThT, to
$\text{A}\beta _{\mathrm {1-42}}$
peptide provides a nanocarrier potentially exemplifying multiple functions, such as magnetic imaging, magnetic handling, drug delivery, fluorescence imaging,
$\text{A}\beta $
binding, and
$\text{A}\beta $
aggregation inhibition.