Tailoring the magnetic hyperthermia performances of gram-bean-extract-mediated highly disperse MFe2O4 (M = Fe, Ni, Mn) nanoferrites

Magnetic hyperthermia requires a long duration of stable therapeutic temperature (43-46 degrees C). Because temperature kinetics mainly depends on the Brownian and Neel relaxation losses of magnetic nanoparticles (MNPs), a thorough control of these losses is essential. This can be achieved by controlling the size, shape, and surface passivation of MNPs. Although extensive studies have been conducted to develop such NPs, a bulk-yield synthesis of highly stable MNPs maintaining stable therapeutic temperatures for a long duration has not been reported. We used an efficient gram-bean-extract-(GBE)-mediated hydrothermal synthesis to obtain a uniform phase-stable bulk production of magnetic nanoferrites, Fe3O4, NiFe2O4, and MnFe2O4 that were smaller than 20 nm. The temperature kinetic plots (TKPs) of the as-hydrothermally (without GBE) synthesized NiFe2O4 and MnFe2O4 NPs (> 20 nm) showed a non-adiabatic increasing trend, which exceeded the safe hyperthermia temperature zone (HTZ; 43-46 degrees C). On the contrary, the GBE-mediated MNPs, particularly MnFe2O4, had faster plateaus earlier in the TKPs, providing the necessary stable HTZ for more than half of the induction heating time. The pectin coatings (from the GBE) on the MNPs passivated the surfaces (preventing oxidation) and reduced the frictional losses (Brownian), which yielded the temperature plateau and stable HTZ at a longer duration. Therefore, the GBE-mediated hydrothermal route can tune the hyperthermia performances to achieve a highly stable HTZ.