Physical investigation and understanding of biomineralisation proteins and their use for the synthesis of new nanomaterials

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Scientific and economic interest in nanotechnology has grown in recent years. Within this the quest to produce tiny and highly tailored magnetic particles, or nanomagnets is crucial. Nanomagnets have a range of practical uses. Historically they have been used for information storage such as tapes and hard drives. Recently this has expanded, with the development of 3D information storage systems providing high density data storage. There is also much interest in the medical applications of nanomagnets. Magnetic particles are being developed to provide targeted medicine within the body. For example, if drugs are tied to nanomagnets at the molecular level then they can be directed by a magnet to specific sites within the patient. This allows a drug to be delivered to a specific area, without harming the rest of the body. Similarly, nanomagnets can be used in hyperthermic therapies. This is where, after being directed to specific tumour sites, magnetic particles are heated to either destroy a tumour or activate a drug. However, as nanotechnology grows, so too does the need to develop precisely engineered nanomagnets. Different applications demand different shapes and sizes of particles and different magnetic properties. Controlling the composition and dimensions of nanomagnets has therefore become a key goal of researchers. Biomineralisation is the process that occurs in living organisms to produce minerals such as bones. Because genetics control biomineralisation processes the materials produced exhibit very precise, uniform and intricate formations down to the nano-scale. Furthermore, if the genetics are understood it may be possible to change with precision the nature of biomineralised materials. Magnetotactic bacteria biomineralise high quality and uniform nanoparticles of the iron-oxide magnetite within biological fatty shells (or vesicles) within the bacterial cell (termed magnetosomes). Because magnetosomes exhibit considerable uniformity and precision they present a novel and attractive route to produce high quality nanoparticles. However, the biomineralisation method can be inefficient for commercial production and is restricted to the specifications imposed by the bacterial cell leaving little flexibility for further modifications. A protein found to be involved in making nanomagnets in the bacteria has previously been extracted, and mass produced (expressed) and used in a chemical precipitation of magnetic particles. The protein was found to control the particle's size and shape even in this chemical production outside the bacterial cell. This research will identify biomineralisation proteins from the genetic information we have about magnetic bacteria, and investigate these proteins individually by expressing then and using them in a chemical formation of nanoparticles similar to the previous study. From this we will study in detail how the protein physically controls the size and shape of the particles using microscopy, spectroscopy and diffraction techniques. These will study the proteins while they are making the particles, so we can identify which parts of the proteins are responsible for the control over formation. With this information we will develop a combined chemical/biological method of making nanomagnetic particles. The new method will combine the benefits of the precision offered by biomineralisation, with the higher yields and more malleable system with respect to variation, offered by chemical synthesis. Furthermore, once the specific role of each protein has been ascertained, particles can be designed and custom-made with the addition of a recipe of the specific proteins and metal ions. This will offer more control over the particles' characteristics than the biological system. This biomimetic synthetic method will allow for the production of particles on a larger, and more commercially viable, scale than if the bacteria alone were used.