Energy Transfer from Magnetic Iron Oxide Nanoparticles: Implications for Magnetic Hyperthermia

Magnetic iron oxidenanoparticles (IONPs) have gainedmomentumin the field of biomedical applications. They can be remotely heatedvia alternating magnetic fields, and such heat can be transferredfrom the IONPs to the local environment. However, the microscopicmechanism of heat transfer is still debated. By X-ray total scatteringexperiments and first-principles simulations, we show how such heattransfer can occur. After establishing structural and microstructuralproperties of the maghemite phase of the IONPs, we built a maghemitemodel functionalized with aminoalkoxysilane, a molecule used to anchor(bio)molecules to oxide surfaces. By a linear response theory approach,we reveal that a resonance mechanism is responsible for the heat transferfrom the IONPs to the surroundings. Heat transfer occurs not onlyvia covalent linkages with the IONP but also through the solvent hydrogen-bondnetwork. This result may pave the way to exploit the directional controlof the heat flow from the IONPs to the anchored molecules i.e.,antibiotics, therapeutics, and enzymes for their activationor release in a broader range of medical and industrial applications.