Factors behind the spontaneous synthesis of spherical brushite from wheat bran aqueous extract: The role of zinc.

Coprecipitation biomineralization was induced using nondialyzed and dialyzed aqueous wheat bran extracts as scaffolds, to which zinc (Zn) was added in a 0%-15% concentration range. Spherical particles of brushite were precipitated up to 3% Zn concentration in the nondialyzed extracts. At 5% and 10% Zn, spherical or spheroidal brushite particles were precipitated, but the internal microstructure changed from stacked plates to laid parallel strands; a secondary weddellite phase was formed. Brushite with 0.018% Zn content was formed even without external additions due to the natural presence of Zn in the nondialyzed extracts. The Zn content of doped brushite particles was between 0.74% and 1% by weight for the 3%-10% added Zn range. Higher concentrations of Zn inhibited crystal growth. In dialyzed extracts, brushite spherical particles were formed only without added external Zn. However, crystal morphology was very similar, and the radial arrangement was maintained. Amorphous material with varied elemental composition precipitated only when Zn was added to the dialyzed extracts. Lattice parameters of brushite were close to those found in the literature, with minor variations for b and c. The results show the evidence of the role of Zn in the spherical morphology of brushite.