Influence of Gold Nanoshell on Hyperthermia of Superparamagnetic Iron Oxide Nanoparticles

A gold nanoshell around superparamagnetic iron oxide nanoparticles (SPIONs) was synthesized, and small-angle X-ray scattering (SAXS) analysis suggests a gold coating of approximately 0.4−0.5 nm thickness. On application of low frequency oscillating magnetic fields (44−430 Hz), a 4−5-fold increase in the amount of heat released with gold-coated SPIONs (6.3 nm size) in comparison with SPIONs (5.4 nm size) was observed. Details of the influence of frequencies of oscillating magnetic field, concentration, and solvent on heat generation are presented. We also show that in the absence of oscillating magnetic field, both SPIONs and SPIONs@Au are not particularly cytotoxic to mammalian cells (MCF-7 breast carcinoma cells and H9c2 cardiomyoblasts) in culture, as indicated by the reduction of 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium by viable cells in a phenazine methosulfate-assisted reaction.