Overgrowth of iron(III) phosphate on collagen

Abstract

The interaction between polymeric matrices and inorganic salts is of considerable interest both for the development of novel materials and for understanding fundamental mechanisms underlying biological mineralization processes. In the present work the overgrowth of iron(III) phosphate dihydrate in aqueous supersaturated solutions at 25 °C, seeded by collagen fibrils was examined. Collagen was found to be an effective nucleator of iron(III) phosphate dihydrate, which was exclusively formed at pH 2.00. Induction times preceding iron(III) phosphate dihydrate precipitation were inversely proportional to the solution supersaturation and a surface energy to 89 mJ m^–2 was calculated from this dependence on the basis of the classical nucleation theory. A comparable value was obtained from precipitation kinetics data. The rates of iron(III) phosphate dihydrate overgrowth were proportional to the solution supersaturation and an apparent order of 2 was obtained for the precipitation process. This value for the order of precipitation along with the strong indication for the existence of fixed active growth sites, may suggest a surface controlled, spiral growth mechanism.