Magnetic particle hyperthermia: nanoparticle magnetism and materials development for cancer therapy

TLDR

Loss processes in magnetic nanoparticles are examined to optimize specific loss power for tumour hyperthermia, noting that field amplitude and frequency limits constrain achievable heating. The study aims to experimentally investigate how alternating field amplitude and frequency affect specific loss power in magnetic nanoparticles for hyperthermia. The authors compare iron‑oxide nanoparticles produced by wet precipitation, grinding, bacterial synthesis, and size fractionation, measuring their structural, magnetic, and specific loss power characteristics across a wide size range to derive guidelines for maximizing SLP. They find that 18‑nm particles with narrow size distribution yield high SLP, bacterial magnetosomes achieve nearly 1 kW g⁻¹, and metallic cobalt particles can surpass this value, with guidelines for maximizing SLP under field constraints.

Abstract

Loss processes in magnetic nanoparticles are discussed with respect to optimization of the specific loss power (SLP) for application in tumour hyperthermia. Several types of magnetic iron oxide nanoparticles representative for different preparation methods (wet chemical precipitation, grinding, bacterial synthesis, magnetic size fractionation) are the subject of a comparative study of structural and magnetic properties. Since the specific loss power useful for hyperthermia is restricted by serious limitations of the alternating field amplitude and frequency, the effects of the latter are investigated experimentally in detail. The dependence of the SLP on the mean particle size is studied over a broad size range from superparamagnetic up to multidomain particles, and guidelines for achieving large SLP under the constraints valid for the field parameters are derived. Particles with the mean size of 18 nm having a narrow size distribution proved particularly useful. In particular, very high heating power may be delivered by bacterial magnetosomes, the best sample of which showed nearly 1 kW g−1 at 410 kHz and 10 kA m−1. This value may even be exceeded by metallic magnetic particles, as indicated by measurements on cobalt particles.