Recent efforts in the area of photothermal therapy (PTT) follow two important aims: (i) selective targeting of plasmonic nanoparticles to the tumor and (ii) real-time guidance of PTT operation through employing multimodal imaging modalities. In the present study, we utilized a multifunctional theranostic nanoplatform constructed from iron (III) oxide-gold (Fe2O3@Au) core-shell nanoparticles to fulfill these aims. The Au shell exhibits surface plasmon resonance, a property that is exploited to realize PTT. The magnetic core enables Fe2O3@Au to be employed as a magnetic resonance imaging (MRI) contrast agent. Furthermore, the magnetic core has the potential to establish a magnetic drug targeting strategy through which Fe2O3@Au can be directed to the tumor site by means of magnetic field. To test these potentials, Balb/c mice bearing CT26 colorectal tumor model were intravenously injected with Fe2O3@Au. Immediately after injection, a magnet was placed on the tumor site for 3 h to concentrate nanoparticles, followed by the near infrared (NIR) laser irradiation. MRI study confirmed the accumulation of nanoparticles within the tumor due to T2 enhancement capability of Fe2O3@Au. The in vivo thermometry results demonstrated that the tumors in magnetic targeting group had a significantly higher temperature elevation rate upon NIR irradiation than non-targeted group (~ 12 °C vs. 8.5 °C). The in vivo antitumor assessment revealed that systemic injection of Fe2O3@Au in combination with magnetic targeting and NIR irradiation resulted in complete remission of tumor growth. Therefore, Fe2O3@Au can establish a targeted PTT strategy for efficient eradication of tumor cells under the guidance of MRI.
Keywords: Cancer; Iron oxide–gold core–shell nanoparticles; Magnetic resonance imaging; Magnetic targeting; Photothermal therapy.