Our project BIOMAG combines bioengineering techniques and subsequent physicochemical anal-yses to generate and characterize magnetic structures in organisms. Due to the fact that magnetic fields can freely penetrate biological tissues, methods enabling non-invasive imaging and control of molecular processes via magnetic fields are highly sought after. Thus, the two research groups (Institute of Biological Imaging (IBMI), Prof. Dr. Gil Westmeyer; Institute of Hydrochemistry (IWC) and Chair of Analytical Chemistry and Water Chemistry, Prof. Dr. Reinhard Niessner and Dr. Natalia P. Ivleva) collaborating for the project BIOMAG aim to develop biomagnetic interfaces for imaging and molecular actuation of mammalian cells. In particular, we show that the protein ferritin can be used both as a contrast agent for Magnetic Resonance Imaging (MRI) and as an interface to facilitate magnetic interaction with mammalian cells.
Ferritin is a universal intracellular iron storage protein of globular spherical shape with an outer and inner diameter of 12 and 8 nm, respectively, harboring an iron core most likely composed of the iron hydroxide ferrihydrite. However, this natural iron core lacks in magnetic properties, and has thus been replaced with the iron oxides maghemite and/or magnetite, both of which show favorable mag-netic characteristics; the resulting protein has been named magnetoferritin. Raman spectra of ferrihydrite, maghemite and magnetite are unique molecular fingerprints, because each mineral consist of a different lattice structure. Therefore, Raman Microspectroscopy (RM) is a suitable non-destructive analytical tool to determine the exact chemical composition of formed bio-minerals, which allows to distinguish various iron oxides and hydroxides inside the ferritin cavity. Once the formation of magnetite inside the ferritin cavity was confirmed with RM, the magnetic properties of magnetoferritin were tested both in vitro and in cell culture. Determination of the relaxivity values confirmed that magnetoferritin is a more sensitive MRI contrast agent than natural ferritin. This observation was further confirmed by loading both proteins on cells, which led to stronger contrast enhancement for magnetoferritin.
Nistler, A., Hartmann, C., Rümenapp, C. et al.: "Production and characterization of long-term stable superparamagnetic iron oxide-shell silica-core nanocomposites", 2017.