Magnetic Nanoparticles in Biomedical Applications

Magnetic nanoparticles are being used in various applications in the life sciences, including magnetic imaging, hyperthermia treatment, drug targeting and blood purification. In the case of a comparison of commercial products that are designed for magnetic imaging, we demonstrate that superparamgnetic particles that are on the boundary to single domain behavior, i.e., those with high susceptibility, show the best contrast properties.

nanopart1 — Relaxivity ratio as a function of (a) the initial slope of the moment normalized magnetization curve, up to 20 mT; and (b) average TS, the temperature for the onset to magnetic blocking.

In other studies, we have examined magnetic properties of magnetic nanoparticles of different compositions and particle sizes, to understand which factors lead to better heating performance. Particles that have high saturation magnetization and low coercivity heat more efficiently with the application of an AC magnetic field.

nanopart2 — Heating efficiency as a function of MS/BC, demonstrating low coercivity leads to more efficient heating in an alternating field.

Collaborations: A.M. Hirt, F. Starsich, & S. Pratsinis (Particle Technology Laboratory, ETHZ); Prof. A. Fink (BioNanomaterials, Adolphe Merkel Institute, Univ. Fribourg); Prof. J. Klohs (Institute for Biomedical Engineering, ETHZ)

F.H.L. Starsich, C. Eberhard, K. Keevend, A. Boss, A.M. Hirt, I.K. Hermann, S.E. Pratsinis, Reduced magnetic coupling in ultra-small iron oxide T1 MRI contrast agents, ACS Applied Bio Materials, 1, 783-791, doi: 10.1021/acsabm.8b00244, 2018.
F.H.L. Starsich, C. Eberhard, A. Boss, A.M. Hirt, I.K. Hermann, S.E. Pratsinis, Coercivity determines magnetic particle heating, Advanced Healthcare Materials, 7, 1800287, doi.org/10.1002/adhm.201800287, 2018.
A.M. Hirt, M. Kumari, D. Heinke, A. Kraupner, Enhanced methods to estimate the efficiency of magnetic nanoparticles in imaging, Molecules, 22, 2204, doi: 10.3390/molecules22122204, 2017.
V. Malik, A. Pal, O. Proavaz, J.J. Crassous, S. Granville, B. Groberty, A.M. Hirt, H. Dietsch, P. Schurtenberger, Hybrid magnetic iron oxide nanoparticles with tunable field-directed self-assembly. Nanoscale, 9, 14405-14413, doi: 10.1039/c7nr04518b, 2017.
F. Crippa, T.L. Moore, M. Mortato, C. Geers, L. Haeni, A.M. Hirt, B. Rothen-Rutishauser, A. Petri-Fink, Dynamic and biocompatible thermo-responsive magnetic hydrogels that respond to an alternating magnetic field. Journal of Magnetism and Magnetic Materials, 427, 212-219, doi: 10.1016/j.jmmm.2016.11.023, 2017.