Zinc ferrite nanoparticles embedded in hydroxyapatite for magnetic hyperthermia and sensitive to ionizing radiation

Here we report the development of a bifunctional magnetic composite that induces magnetic hyperthermia and shows stable paramagnetic defects after the irradiation with X-ray source. The composite is formed by Zn0.16Fe2.84O4 nanoparticles of 18 (3) nm of diameter embedded in a micrometric carbonated hydroxyapatite matrix. As the magnetic nanoparticles are fixed in the matrix, their magnetic properties were adjusted by the size and composition in order to induce local heating by magnetic losses in presence of an AC magnetic field due to the Neel relaxation mechanism. This behavior was confirmed by measuring the Specific Power Absorption (SPA) of 0.1 wt% of magnetic nanoparticles dispersed in media with different viscosity as chloroform (eta = 0.56 cP) and butter oil (eta = 174 cP) obtaining ~111(15) W/g in both cases. Consistently, the magnetic hydroxyapatite composite presents a comparable SPA= 126(19) W/g value. On the other hand, the carbonated hydroxyapatite and the magnetic carbonated hydroxyapatite composite were subjected to X-ray radiation with an equivalent dose of 3 kGy and the generated paramagnetic defects were evaluated by electron paramagnetic resonance spectroscopy. It was observed that the CO2 radical is the main defect produced by the irradiation, and its concentration stabilized after a month. These results confirm the potential of this composite to act as a local nanoheater and as a sensor of ionizing radiation, showing interesting possibilities to be used in studies of nanomedicine where the combination of magnetic hyperthermia and radiotherapy is proposed for oncological treatments. (C) 2022 Elsevier B.V. All rights reserved.