Specific characteristics of wet nanocrystalline apatites. Consequences on biomaterials and bone tissue

The analysis of wet nanocrystalline apatites by spectroscopic techniques (FTIR, solid state NMR) reveals fine, transient, structural details testifying for the existence of a structured hydrated layer on the surface of nanocrystals probably related although not identical, to the structure of octacalcium phosphate. On drying this layer loses its very fragile structure and gives a disordered assembly of ions corresponding to non-apatitic environments. The existence of a hydrated layer with mobile ionic entities due to an enhanced surface reactivity, gives nanocrystalline apatites very specific and interesting properties, which are used by living organisms in mineralised tissue and which can be utilised in material science. They allow strong intercrystalline interactions, specific adsorption properties and adhesion to other surfaces.