Molecular Principles Underlying Biomineralization Pathways and Biomimetic Strategies by Solid State NMR

Biomineralization provides numerous and diverse examples where organisms have optimized processes of growth of solid nanophases, both crystalline and amorphous, so that high-performing ceramics are synthesized at ambient temperatures in aqueous conditions yielding materials that are functionally-tailored. Essential to the process is control over all aspects of the resulting biogenic inorganic material, from molecular structure and composition through macroscopic shape, morphology, mechanical and optical properties, stability and more. Of key importance is the elucidation of the atomistic details of the resulting intact biominerals, and of the mechanisms which encode functionality into these materials; e.g. which imprint either for stability or metastability. Many methodologies provide access to mineral properties as a function of growth conditions; but their characterization in terms of atomistic structures and interactions is difficult to address except by solid-state NMR (ssNMR). Our NMR studies expose the structural-chemical state of inorganic-bioorganic interfaces, as in “intracrystalline” mineral-occluded bioorganics, where we directly probe their chemical identity and the interactions between the different components and follow them forward as the materials form, phase separate or transform despite their low concentration, their fundamentally disordered nature, and that they are buried within bulk matrices.

Earlier molecular insights into the mechanisms employed by coccolithophores (intracellular construction of calcitic coccoloiths) and fresh water crayfish (gastroliths - storage organs of bioavailable amorphous calcium carbonate, ACC) will be reviewed. Following, I will describe recent in vitro studies of the mechanisms by which phosphate and water molecules regulate the stability of ACC, and by which biomolecules (Asp, Glu) in the precipitations solution and therein occluded in the lattice control and imprint its characteristics. Both in vitro biomimetic model systems demonstrate fundamental biomineralization pathways.