Introducing SMART RHESINs: a novel tracer design for future quantitative magnetic particle imaging (MPI)

Abstract

Magnetic particle imaging (MPI) is a promising modality in medical imaging leveraging magnetic properties of nanoparticles [1]. So far, mainly commercially available or core/shell nanoparticles have been used [2], but the development of specific MPI tracers promises a better signal detection and opens up new possibilities in biomedicine. In our study, we introduce SMART RHESINs, an innovative tracer architecture specifically designed for MPI [3]. In SMART RHESINs, superparamagnetic nanoparticles (MNPs) with a size of ca. 8 nm are encapsulated in hollow polymer nanospheres with sizes from 150-300 nm. This encapsulation shields MNPs from external factors, ensuring viscosity-independent relaxation of magnetic moment vectors, enabling reliable signal quantification irrespective of the surrounding medium. These tracers not only exhibit superparamagnetic properties, but are also luminescent and do not adversely affect cell viability. The surface of these nanoparticles incorporates functional groups facilitating further customization for e.g., targeted applications. SMART RHESINs are therefore ideal as bimodal imaging tracers for e.g., cancer diagnosis and treatment. Our findings suggest that SMART RHESINs can significantly broaden the application of Magnetic Particle Spectroscopy (MPS) and MPI, offering a modular tracer platform with implications for various physical and biomedical scenarios. This MPI-novel nanoparticle design contributes to the advancement of quantitative MPI techniques.