Magnetically tunable iron oxide nanotubes for multifunctional biomedical applications

Design of a multifunctional magnetic bionanosystem has become increasingly important towards advancing the future of clinical medicine. While hollow iron oxide nanoparticles with enhanced surface areas allow for more drug molecules to be attached to the particles, their relatively low saturation magnetization (M-s) hinders their practicality in medicinal applications such as drug delivery and hyperthermia therapy. We demonstrate that this limitation can be overcome by utilizing 1D magnetic nanotubes that possess both enhanced surface areas and high M-s. In this study, highly crystalline, tunable aspect ratio Fe3O4 nanotubes have been successfully synthesized using a hydrothermal method. Magnetic measurements showed a clear Verwey transition (similar to 120 K) and high M-s (similar to 75 emu/g) at 300 K, confirming the high quality of the synthesized Fe3O4 nanotubes. Calorimetric experiments on randomly dispersed Fe3O4 nanotubes in water with concentration of 1 mg/mL showed a large Specific Absorption Rate (SAR) value of 400 W/g for an AC magnetic field of 800 Oe, which increased to 500 W/g when the nanotubes were aligned parallel to the DC magnetic field and suspended in a 2% agar solution. Our study shows the possibility of using the Fe3O4 nanotubes as a highly effective multifunctional nanoscale tool for targeted hyperthermia and on-demand drug delivery. (C) 2019 Elsevier B.V. All rights reserved.