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Physics, chemistry and biology of Soft Matter
Paper
J. Mater. Chem., 1999, 9, 2573 - 2582, DOI: 10.1039/a901309a
The functionalization of titanium with EDTA to induce biomimetic mineralization of hydroxyapatite
Chuanbin Mao, Hengde Li, Fuzhai Cui, Qinglin Feng and Chunlai Ma
A new process is developed to functionalize an inorganic substrate with an organic polycarboxylic chelating agent to obtain a biomimetic template for mimicking biomineralization for the synthesis of films or coatings. A titanium plate is first placed in ethylenediaminetetracetic acid (EDTA) solution to effect chemisorption and self-assembly of EDTA molecules on the plate. The plate is then aged in supersaturated hydroxyapatite [(Ca10(PO4)6(OH)2, HA] solution to mimic biomineralization. The functionalization process is found to be very effective in creating a surface with an organized arrangement of carboxylate ions (–COO–) with the orientation of lone pairs of electrons on O perpendicular to or radiating from the substrate surface. The coating is formed through the plate-like outgrowth of HA grains along the [001] direction under the mediation of the functionalized surface, giving rise to the coexistence of two kinds of microstructural patterns in coating. One is a parallel arrangement of the plate-like HA grains with (001) planes preferably parallel to the substrate surface, the other is a radial arrangement of the plate-like HA grains with the [001] direction radiating from one surface core and the (111) planes preferably parallel to the surface. The mineralization mechanism is discussed on the basis of the conformation of the self-assembled EDTA molecules and the interfacial molecular recognition, analogous to the biomineralization, including electrostatic interactions, hydrogen bonding, stereochemical arrangement and geometrical correspondence.
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