A magnetic composite FA@Fe3O4 is formed by coupling magnetic iron oxide (Fe3O4) with folic acid (FA) through a facile hydrothermal synthesis process. The morphology, particle size, elemental composition, and magnetocaloric properties have been characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffractometry (XRD), vibrating sample magnetometry (VSM), X-ray photoelectron spectrometry (XPS), and Fourier transform infrared spectroscopy (FTIR). Microscopic images showed that the Fe3O4 NPs were spherical, and their average size could be tuned from 13 ± 4 nm to 230 ± 4 nm by varying the OAm/EG ratio. According to the FTIR and XPS results, FA was chemically bonded to the amide bond on the surface of Fe3O4. The particles display ferromagnetic characteristics. Notably, FA@Fe3O4 retains favorable magnetic properties after FA modification, showing superparamagnetic behavior with a saturation magnetization of 64–69 emu/g. Although this value is somewhat lower than that of unmodified Fe3O4 (71.0 emu/g), no significant degradation in the magnetic performance was observed. According to the results of the MTT cytotoxicity evaluation experiment, FA@Fe3O4 exhibits low cytotoxicity (cell viability >80% at 0.25 mg/mL). What is more, FA@Fe3O4 magnetic fluid has good stability and superparamagnetic properties and is expected to mediate targeted hyperthermia therapy for malignant tumors.
Wang et al. (2026) studied this question.