Magnetic nanoparticles (MNP) suitable for biomedical applications require specifically designed physicochemical properties. Most importantly, biological compatibility represents the key prerequisite for production of safe nanobiomaterials and, thus for unbiased applications inside neuronal cells. Biochemical recognition elements at the nanoparticle surfaces enables site-specific functionalization with biologically active molecules. Furthermore, engineered membrane permeability facilitates nanoparticles delivery into the cytoplasm. Finally, MNPs are required to sensitively respond to magnetic field gradient to allow remote control of cellular functions inside patients. Fluorescent reporter for localizing MNPs inside cells are ideal for systematically optimizing intracellular properties and magnetic responses.
The combination of all these features in one object that is ~5000 times smaller than the diameter of a hair is the challenge of WP3. To this end, we are developing the production of semi-synthetic MNP based on combining engineered biomaterials. We utilize naturally occuring protein nanocages as a scaffold for synthesis of magnetic nanoparticles (MNPs) by mimicking a natural biochemical process in vitro. This approach yields MNPs with intrinsically biological identity. The green fluorescent protein (GFP), which is proven to be non-toxic, is fused to the surface of MNPs by genetic engineering. GFP is exploited as fluorescent reporter and for site-specific capturing of proteins to the MNP surface.
For this purpose, proteins to manipulate neuronal signalling are fused to a nanobody against GFP, which ensures fast and highly specific capturing to the GFP-coated MNPs. By engineering a viral protein transduction domain into the GFP, we furthermore aim to achieve efficient transfer across the cell outer membrane. Similar strategies are adapted to synthetic MNP with the aim to produce and to establish safe and potent magnetic nanobiomaterials for remote-controlled actuation of signalling pathways inside living cells.