Bifunctional Gold Nanoshells with a Superparamagnetic Iron Oxide−Silica Core Suitable for Both MR Imaging and Photothermal Therapy

Abstract

We describe the synthesis, characterization, and use of hybrid nanoparticles with a superparamagnetic iron oxide (SPIO)−silica core and a gold nanoshell. These multifunctional nanoparticles, designated SPIO−Au nanoshells, displayed superparamagnetic characteristics and a significant absorbance in the near-infrared (NIR) region of the electromagnetic spectrum. In addition, they exhibited high transverse relaxivities, R 2, and a large R 2 / R 1 ratio, and therefore, they could be imaged by MRI to obtain T 2 -weighted images. Moreover, the SPIO−Au nanoshells showed efficient photothermal effects when exposed to NIR light. The use of SPIO−Au nanoshells, with their combination of unique magnetic and optical properties, should enhance the efficacy of nanoshell-mediated photothermal therapy by making it possible to direct more nanoparticles to tumors through the application of external magnetic field and by permitting real-time in vivo MRI imaging of the distribution of the nanoparticles before, during, and after photothermal therapy.