Metastable equilibrium solubility behavior of bone mineral

Area of Science:

• Biomineralization
• Bone Physiology
• Materials Science

Background:

• Carbonated apatites (CAP) display metastable equilibrium solubility (MES) distributions.
• Bone mineral's solubility behavior requires further investigation using MES concepts.

Purpose of the Study:

• Investigate bone mineral solubility using MES distributions.
• Compare bone mineral to synthetic CAP, considering crystallinity and composition.
• Identify the governing function for bone mineral and CAP dissolution.

Main Methods:

• Harvested bone samples from rats of varying ages (1, 5, 8 months).
• Deproteinated bone samples using hydrazine.
• Synthesized CAP via dicalcium phosphate dihydrate (DCPD) hydrolysis.
• Determined MES distributions by equilibrating samples in buffered solutions at various pHs.
• Calculated ion activity products for octacalcium phosphate, hydroxyapatite, and CAP stoichiometries.

Main Results:

• Bone mineral exhibits MES distribution phenomena.
• Changes in bone mineral crystallinity with age correlated with MES values.
• A synthetic CAP closely mimicked the physicochemical behavior of 8-month-old rat bone mineral.
• Hydroxyapatite stoichiometry accurately described MES results for both CAP and bone mineral.
• Surface complex with hydroxyapatite stoichiometry governs bone mineral solubility.

Conclusions:

• Bone mineral solubility behavior is governed by a surface complex with hydroxyapatite stoichiometry.
• Metastable equilibrium solubility distributions are characteristic of bone mineral.
• Synthetic CAP can serve as a model for bone mineral physicochemical properties.