Oxygen vacancy enhanced magnetic heating efficiency of ferrite nanoparticles for self-regulating temperature hyperthermia

Precise and controllable temperature is required for using magnetic hyperthermia in cancer therapy. Magnetic nanoparticles typically need to have a Curie temperature of 42–50 °C to self-regulate hyperthermia temperature via magnetic phase transition. For now, the most studied iron oxide nanoparticles are not suitable for self-regulating hyperthermia applications due to their high Curie temperature of several hundred Celsius degrees. Doping nonmagnetic metal ions into iron oxide nanoparticles is an effective way to decrease Curie temperature, but often leads to low saturation magnetization and poor magnetic heating efficiency, limiting its usage in hyperthermia applications. Magnetic nanoparticles with excellent magnetic heating efficiency and suitable Curie temperature are highly desirable. This paper proposes an approach for enhancing magnetic heating efficiency by regulating oxygen vacancy concentration. Mn0.46Zn0.54Al0.25Fe1.75O4 nanoparticles with Curie temperature at 44.5 °C are prepared by co-precipitation method. Effective regulation of oxygen vacancy concentrations is achieved through hydrogen peroxide oxidation and carbothermal reduction treatments. Research results suggest that increasing oxygen vacancies significantly enhance the magnetism due to the transformation of magnetic couplings on nanoparticles, while barely affecting the Curie temperature. These nanoparticles exhibit high magnetic heating efficiency under an alternating magnetic field, almost 1.5 times of clinical-grade iron oxide nanoparticles, and can self-regulate hyperthermia temperature at 48–49 °C. This work may provide some references for further research on self-regulating temperature magnetic hyperthermia.