Linear magnetic nanoparticle structures for theranostic applications of nanomodified implants in magnetic particle imaging and magnetic hyperthermia

Abstract

Magnetic particle imaging (MPI) combined with magnetic hyperthermia (MH) is a promising hybrid modality for theranostic applications. It enables localized and controlled heat deposition in the target area and allows accurate treatment planning. In this regard it must be considered that the MPI signal and MH heating output is dependent on magnetic nanoparticle (MNP) interactions and MNP mobility. For MNP immobilized in implants, these effects have a tremendous impact on the quality of diagnosis and therapy.
In fiber-based implants, linear MNP agglomerations are formed during production, which are roughly aligned with the major axis direction of the fibers. The MPI and MH investigations of these fibers showed that the MPI frequency spectrum of the MNP signal is dependent on the fiber orientation relative to the direction of the excitation field. This effect was attributed to the interaction between the linearly aligned MNP inside the fibers. The results were confirmed by independent measurements with linearly aligned MNP inside hydrogels. In accordance with experimental results, simulation showed the same trends on MPI and MH heating output. The determined influence of the interactions must therefore be considered for future models. Based on extensive investigations, it will be possible to develop a model that reliably reflects the relations between measured signals and the MNP properties of the linear structures and thus enables accurate MPI images and prediction of MNP heating behavior inside the implants.