Leeds Centre for Crystallization

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Biomineralization

Biomineralization describes the production of inorganic solids by organisms, and is extremely common in nature, with over 60 biominerals having been identified among all five of the animal kingdoms.

Bones, teeth and seashells are common examples. Of known minerals, approximately 20% are amorphous and 80% crystalline, although the number of amorphous minerals may be an underestimate due to the problems of detecting amorphous materials in the presence of crystalline ones.

Biominerals are typically characterised by unique morphologies, and display properties optimised for their function. For example, biominerals fulfilling structural roles typically possess remarkable mechanical properties which can rival those of engineering materials. The magnetite crystals providing magnetotactic bacteria with a magnetic dipole and enabling navigation in the earth’s magnetic field are always a single magnetic domain in size. Of note also is the ability of organisms to selectively precipitate minerals such as SrSO4 and BaSO4 that are significantly undersaturated in the surrounding environment of the organism.

Perhaps the most immediately striking aspect of biominerals is the range of truly exquisite and elaborate morphologies observed, which are frequently entirely disparate from their synthetic counterparts. Structurally, biominerals are typically composite materials, being intimately associated with organic macromolecules, and are often hierarchically organised on a scale from Angstroms to millimeters. The organic macromolecules are a vital component of the mineral, being involved in nucleation and growth control, and definition of mechanical properties. In consequence, although precipitated under ambient conditions, biominerals often exhibit superior mechanical properties, which is particularly important when they are being exploited for skeletal roles.

Nature clearly achieves this remarkable degree of control over crystallization at low temperature, atmospheric pressure and with mild reaction conditions.  Identification of the strategies used by Nature to generate biominerals can therefore enable us to control biomineralization in the body, leading for example to bone and tooth regeneration.  We can also profit from these strategies to develop novel, green, materials syntheses which operate under ambient conditions.

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