(489b) Flame Aerosol Synthesis of Doped Iron Oxide Nanoparticles As Tracers with High Resolution for Magnetic Particle Imaging

Magnetic particle imaging (MPI) is an emerging diagnostic technique that uses the signal generated solely from superparamagnetic iron oxide nanoparticles (SPIONs). MPI has shown great potential in tumor imaging, cell tracking, and angiography due to its excellent sensitivity, contrast, and safety profile.¹ The biocompatibility of MPI tracers offer additional advantage over other imaging techniques that use harmful ionizing radiation or toxic compounds. However, MPI faces challenges due to its lower resolution compared to other imaging modalities. The MPI signal can be enhanced by tailoring tracer properties such as magnetic moment, saturation magnetization, and anisotropy. An effective approach to modulate these properties is to incorporate elements such as cobalt, nickel, zinc, and magnesium in the SPION lattice.¹ Although, synthesis of MPI tracers with complex stoichiometry presents challenges for large-scale production, it can be circumvented by flame spray pyrolysis (FSP),² a scalable manufacturing technique. This study reports a comprehensive investigation of doped SPIONs as MPI tracers while demonstrating the suitability of FSP for their scalable synthesis.

SPIONs doped with manganese and zinc were synthesized by FSP in two crystal size groups (13-16 nm and 22-33 nm) and their MPI performance was evaluated using the MOMENTUM MPI scanner. Post-synthesis functionalization of the nanoparticle surface with citrate and subsequent filtration significantly enhanced the MPI resolution of SPIONs, with Zn-doped nanoparticles exhibiting the highest resolution. These findings signify the influence of hydrodynamic size, size distribution, and SPION composition on the MPI resolution. 2D MPI scans revealed that small-sized Zn-doped SPIONs exhibited optimal MPI performance, characterized by high resolution and sensitivity. The overall MPI performance of all tracers was closely linked to their hydrodynamic size, magnetic diameter, and susceptibility. Finally, as a proof-of-principle, Zn-doped SPIONs were encapsulated in a water-dispersible nanocarrier using flash nanoprecipitation (FNP), circumventing the need for citrate coating while preserving the MPI performance of the tracer. These findings emphasize the significance of doped SPIONs for improved MPI performance, and highlight the combined potential of FSP and FNP in large-scale production of MPI tracers.

Acknowledgement:

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 101002582). The authors also acknowledge financial support from the Science for Life Laboratory.

References:

(1) Xie, X.; Zhai, J.; Zhou, X.; Guo, Z.; Lo, P.-C.; Zhu, G.; Chan, K. W. Y.; Yang, M.; Xie, X.; Zhai, J.; Zhou, X.; Lo, P.-C.; Yang, M.; Guo, Z.; Zhu, G.; Chan, K. W. Y. Magnetic Particle Imaging: From Tracer Design to Biomedical Applications in Vasculature Abnormality. Adv. Mater. 2023, 2306450.

(2) Mädler, L.; Kammler, H. K.; Mueller, R.; Pratsinis, S. E. Controlled Synthesis of Nanostructured Particles by Flame Spray Pyrolysis. J. Aerosol Sci. 2002, 33 (2), 369–389.