Synthesis and Characterization of Zn‐Doped Fe ₃ O ₄ Nanoparticles for Magnetic Hyperthermia: In Vitro Test Against Thermoresistant <i>Pseudomonas aeruginosa</i> and <i>Candida albicans</i>

ABSTRACT Superparamagnetic iron oxide nanoparticles (SPIONs) present significant potential for magnetic fluid hyperthermia (MFH) therapies, owing to their high magnetic saturation, superior colloidal stability, and crystallinity. This work reports the solvothermal synthesis of Zn‐doped Fe 3 O 4 nanoparticles, which demonstrated high crystallinity and a saturation magnetization of 71.40 emu g −1 . Under alternating magnetic fields (AMFs), a suspension of these nanoparticles (15 mg mL −1 ) achieved temperature increments of 11.65°C and 23.92°C at applied field conditions of 166.12 kHz/13.24 kA m −1 and 263.6 kHz/13.91 kA m −1 , respectively. These MFH conditions subsequently induced the release of ferrous/ferric ions at concentrations of 3.76 and 11.86 mg L −1 . The efficacy of the MFH treatment, driven by the nanoparticles, was evaluated against the pathogens Pseudomonas aeruginosa (thermoresistant bacteria) and Candida albicans . The study revealed a biphasic antimicrobial mechanism: initially, microbial growth occurs due to the release of iron ions, which microbes use for natural survival; this is followed by cytotoxic effects, combined with direct thermal ablation and the generation of reactive oxygen species (ROS), resulting in potent microbial inhibition.