Iron-gold (Fe2O3@Au) core-shell nano-theranostic for magnetically targeted photothermal therapy under magnetic resonance imaging guidance

Introduction: Photothermal therapy (PTT) is a nanotechnology-assisted cancer hyperthermia approach in which the interaction between laser light and plasmonic nanoparticles generates a localized heating for thermoablation of the tumor. Recent efforts in the area of PTT follow two important aims: (i) exploitation of targeting strategies for preferential accumulation of plasmonic nanoparticles within the tumor and (ii) enabling real-time guidance of PTT operation through employing multimodal imaging modalities. Materials and Methods: In the present study, we utilized a multifunctional theranostic nanoplatform constructed from a magnetic core and Au shell (Fe2O3@Au) in order 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 used as magnetic resonance imaging (MRI) contrast agent. Furthermore, the magnetic core can also be used to achieve a magnetic drug targeting strategy through which Fe2O3@Au would be concentrated in the tumor site by means of magnetic field. Balb/c mice bearing CT26 colorectal tumor model were intraperitoneally injected with Fe2O3@Au. Immediately after injection, a magnet (magnetic field strength of 0.4 Tesla) was placed on the tumor site for 6 hours in order to concentrate Fe2O3@Au, and thereafter the tumors were irradiated with the near infrared (NIR) laser source (808 nm; 2 W/cm2; 3 min). This experiment was conducted for three sessions. Results: MRI confirmed the accumulation of nanoparticles within the tumor due to T2 enhancement capability of Fe2O3@Au. The temperature of the tumors without magnetic targeting was increased by ~7°C after NIR irradiation, whereas the tumors in magnetic targeting group showed a temperature rise of ~12°C. Conclusion: The in vivo antitumor assessment revealed that intraperitoneal injection of Fe2O3@Au nanoparticles and their targeting via magnetic field toward the tumor followed by NIR irradiation remarkably inhibited tumor growth and induced extensive necrosis. Therefore, Fe2O3@Au can establish a targeted MRI-guided PTT strategy.