Hydroxyapatite [HA, Ca10(PO4)6(OH)2] is the main constituent of the mineral phase in mammalian bones and teeth enamel. In the present work, in order to study the interfacial reactions between HA and bioglasses (Hench’s mechanism), ab-initio electronic structure methods have been applied to describe hydroxyapatite (001) and (100) surfaces, with the periodic ab-initio CRYSTAL code (Gaussian basis set and B3LYP functional). Actually, HA growth is elongated in the [0001] direction in bone matrix and in tooth enamel, but it is known that some proteins (e.g., multiphosphorylated) bind preferentially to (100) crystal faces. Models with different thickness have been characterised, both free and in interaction with water molecules (Figure). The computed water binding energy is ~20/30 kcal/mol, in agreement with microcalorimetric data. The calculated vibrational frequencies of adsorbed water, in comparison with those of free water, show a remarkable agreement with the experimental IR data. For the future, we will aim at modelling amino acids adsorptions and at simulating the interaction between HA and silica based materials, thus approaching to Hench’s reaction steps.
Calcium hydroxyapatite in bioglasses: ab-initio characterization of free (001) and (100) surfaces and their interaction with water
UGLIENGO, Piero;CORNO, MARTA;
2005-01-01
Abstract
Hydroxyapatite [HA, Ca10(PO4)6(OH)2] is the main constituent of the mineral phase in mammalian bones and teeth enamel. In the present work, in order to study the interfacial reactions between HA and bioglasses (Hench’s mechanism), ab-initio electronic structure methods have been applied to describe hydroxyapatite (001) and (100) surfaces, with the periodic ab-initio CRYSTAL code (Gaussian basis set and B3LYP functional). Actually, HA growth is elongated in the [0001] direction in bone matrix and in tooth enamel, but it is known that some proteins (e.g., multiphosphorylated) bind preferentially to (100) crystal faces. Models with different thickness have been characterised, both free and in interaction with water molecules (Figure). The computed water binding energy is ~20/30 kcal/mol, in agreement with microcalorimetric data. The calculated vibrational frequencies of adsorbed water, in comparison with those of free water, show a remarkable agreement with the experimental IR data. For the future, we will aim at modelling amino acids adsorptions and at simulating the interaction between HA and silica based materials, thus approaching to Hench’s reaction steps.
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