Self-assembly of hierarchical magnetic nano- to microstructures: biogenic and biomimetic synthesis of magnetite chains
Magnetotactic bacteria form intracellular chains of magnetosomes, which display a hierarchically ordered nano- and microstructure over several levels, up to the magnetic control of coordinated alignment and motility of entire populations of cells. The bacterial magnetic structures are formed by biomineralization from membrane-enveloped, biomineralized magnetic nanocrystals, which in turn by self-assembly align into more complex structures. Bacterial magnetosome formation is under strict biological control, which is associated with unprecedented material properties. However, despite of enormous efforts by material sciences, the biogenic magnetic nanoparticles, and in particular, the resulting complex magnetic structures have not been replicated yet by conventional technological approaches. In this project, we suggest a biomimetic approach for the synthesis of hierarchically structured magnetic nanomaterials, which is inspired by the bacterial system. After identification and thorough characterization of the relevant structures and molecular building blocks, we aim to reconstitute in vitro the assembly of magnetic nanocrystals purified from bacteria. In particular, this will involve the bacterial proteins MamK and MamJ which are known to collectively form the cytoskeletal network controlling alignment of magnetosome chains in vivo. Next, biological constituents of the system will be partially substituted and combined with novel material components, such as modified polymeric structures and biomimetic magnetic nanoparticles. Ultimately, we will apply the principles of biological assembly to design hierarchically ordered two- and three-dimensional nano- and microstructures with novel and tailored mechanical, physico-chemical, and magnetic material characteristics.