Iron Oxide-Gold Core-Shell Nanoparticles as Multimodal Imaging Contrast Agent

Nanoparticles (NPs) are emerging as a potential medical tool for novel diagnostic, drug delivery, and therapeutic approaches. Among them, a spherical NP with a core-shell structure is a way to combine multiple functionalities on the nanoscale. In this paper, we describe the preparation characterization and applications of core-shell iron oxide-gold nanoparticles (<formula formulatype="inline"><tex Notation="TeX">${\rm Fe}_{3}{\rm O}_{4}$</tex></formula>@Au NPs). A comprehensive set of experiments, including transmission electron microscopy, dynamic light scattering, small angle neutron scattering, and ultraviolet visible spectroscopy is applied to characterize their chemical, physical, and optical properties. We also study their applicability as contrast agents for magnetic resonance imaging (MRI): the measurement of longitudinal and transverse relaxation times of <formula formulatype="inline"><tex Notation="TeX">${\rm Fe}_{3}{\rm O}_{4}$</tex></formula>@Au NPs in vitro and in vivo allowed the assessment of longitudinal <formula formulatype="inline"><tex Notation="TeX">$({\rm R}_{1})$</tex></formula> and transverse <formula formulatype="inline"> <tex Notation="TeX">$({\rm R}_{2})$</tex></formula> relaxivities at 1.5 and 3 T. Finally, a procedure for functionalizing NPs with integrin targeting cyclic Arginine-Glycine-Aspartate peptidomimetic is reported, leading to the development of nanoscale probes for <formula formulatype="inline"><tex Notation="TeX">$\alpha_{v}\beta_{3}$</tex></formula> integrin, particularly attractive in terms of resolution and 3-D imaging capabilities. The resulting multifunctional nanoprobes offer suitable blood-circulation time and contrast for microimaging as well as for gradient-echo MRI, and could enable new imaging magnetoplasmonic applications.