Nanoflowers versus magnetosomes: comparison between two promising candidates for magnetic hyperthermia therapy

Magnetic Fluid Hyperthermia mediated by iron oxide nanoparticles is one of the mostpromising therapies for cancer treatment. Among the different candidates, magnetite and maghemite nanoparticles have revealed to be some of the most promising candidates due to both their performance andtheir biocompatibility. Nonetheless, up to date, the literature comparing the heating efficiency of magnetiteand maghemite nanoparticles of similar size is scarce. To fill this gap, here we provide a comparison between commercial Synomag Nanoflowers (pure maghemite) and bacterial magnetosomes (pure magnetite)synthesized by the magnetotactic bacterium Magnetospirillum gryphiswaldenseof〈D〉 ≈40–45 nm. Bothtypes of nanoparticles exhibit a high degree of crystallinity and an excellent degree of chemical purity andstability. The structural and magnetic properties in both nanoparticle ensembles have been studied by meansof X–Ray Diffraction, Transmission Electron Microscopy, X–Ray Absorption Spectroscopy, and SQUIDmagnetometry. The heating efficiency has been analyzed in both systems using AC magnetometry at severalfield amplitudes (0–88 mT) and frequencies (130, 300, and 530 kHz).This work was supported in part by the Spanish 'Ministerio de Ciencia, Investigación y Universidades' under Project MAT2017-83631-C3-R, and in part by the Nanotechnology in Translational Hyperthermia (HIPERNANO) under Grant RED2018–102626–T. The work of Elizabeth M. Jefremovas was supported by the Beca Concepción Arenal through the Gobierno de Cantabria–Universidad de Cantabria under Grant BDNS: 406333. The work of Irati Rodrigo was supported by the Programa de Perfeccionamiento de Personal Investigador Doctor (Gobierno Vasco) under Grant POS–2020–1–0028 and Grant IT–1005–16. The work of Lourdes Marcano was supported by the Postdoctoral Fellowship from the Basque Government under Grant POS–2019–2–0017