Maximizing Specific Loss Power for Magnetic Hyperthermia by Hard–Soft Mixed Ferrites

Maximized specific loss power and intrinsic loss power approaching theoretical limits for alternating-current (AC) magnetic-field heating of nanoparticles are reported. This is achieved by engineering the effective magnetic anisotropy barrier of nanoparticles via alloying of hard and soft ferrites. 22 nm Co_0.03Mn_0.28Fe_2.7O₄/SiO₂ nanoparticles reach a specific loss power value of 3417 W g⁻¹ _metal at a field of 33 kA m⁻¹ and 380 kHz. Biocompatible Zn_0.3Fe_2.7O₄/SiO₂ nanoparticles achieve specific loss power of 500 W g⁻¹ _metal and intrinsic loss power of 26.8 nHm² kg⁻¹ at field parameters of 7 kA m⁻¹ and 380 kHz, below the clinical safety limit. Magnetic bone cement achieves heating adequate for bone tumor hyperthermia, incorporating an ultralow dosage of just 1 wt% of nanoparticles. In cellular hyperthermia experiments, these nanoparticles demonstrate high cell death rate at low field parameters. Zn_0.3Fe_2.7O₄/SiO₂ nanoparticles show cell viabilities above 97% at concentrations up to 500 µg mL⁻¹ within 48 h, suggesting toxicity lower than that of magnetite.