Hyperthermia of Magnetic Nanoparticles: Experimental Study of the Role of Aggregation

Magnetic hyperthermia is a promising tool as an adjuvant therapy for multimodal cancer treatment. However, the heating efficiency of magnetic nanoparticles in biological conditions remains poorly understood, especially regarding the influence of their dispersion state. In this work, dynamic light scattering (DLS) and hyperthermia experiments were coupled to highlight the role of aggregation of iron oxide nanoparticles on their heating properties. Bare, poly(acrylic acid) coated, and poly(acrylic acid- co -maleic acid) coated nanoparticles were studied. Interparticular interactions were investigated by varying both ionic strength and pH. Our results show that the specific loss power (SLP) of nanoparticles in small loose aggregates is similar to that of well-dispersed nanoparticles while the formation of large and dense aggregates observed by DLS leads to a significant decrease of the SLP. However, for intermediate aggregation states, DLS experiments alone do not allow fully grasping the links between heating properties and aggregation. Small angle X-ray scattering experiments (SAXS) were then performed to get further information about aggregate structure. It appears that the compactness of aggregates plays a crucial role, with closer nanoparticles leading to a more important decrease of heating efficiency.