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Abstract:
Fully green and facile redox chemistry involving reduction of colloidal
iron hydroxide (Fe(OH)(3)) through green tea (GT) polyphenols produced
water-soluble Fe3O4 nanocrystals coated with GT extracts namely
epigallocatechin gallate (EGCG) and epicatechin (EC). Electron donating
polyphenols stoichiometrically reduced Fe3+ ions into Fe2+ ions
resulting in the formation of magnetite (Fe3O4) nanoparticles and
corresponding oxidized products (semiquinones and quinones) that
simultaneously served as efficient surface chelators for the Fe3O4
nanoparticles making them dispersible and stable in water, PBS, and cell
culture medium for extended time periods. As-formed iron oxide
nanoparticles (2.5-6 nm) displayed high crystallinity and saturation
magnetization as well as high relaxivity ratios manifested in strong
contrast enhancement observed in T-2-weighted images. Potential of green
tea-coated superparamagnetic iron oxide nanocrystals (SPIONs) as
superior negative contrast agents was confirmed by in vitro and in vivo
experiments. Primary human macrophages (J774A.1) and colon cancer cells
(CT26) were chosen to assess cytotoxicity and cellular uptake of GT-,
EGCGq-, and ECq-coated Fe3O4 nanoparticles, which showed high uptake
efficiencies by J774A.1 and CT26 cells without any additional
transfection agent. Furthermore, the in vivo accumulation
characteristics of GT-coated Fe3O4 nanoparticles were similar to those
observed in clinical studies of SPIONs with comparable accumulation in
epidermoid cancer-xenograft bearing mice. Given their promising
transport and uptake characteristics and new surface chemistry,
GT-SPIONs conjugates can be applied for multimodal imaging and
therapeutic applications by anchoring further functionalities.
