Inorganic plasma with physiological CO2/HCO3− buffer

The substitution of tris/HCl buffer by CO2/HCO3− buffer in inorganic plasma was studied. An appropriate gas mixture of CO2/N2 was continuously bubbled in Kokuboʹs SBF solution prepared without addition of Tris/HCl. This method enables buffering the solution within the 7.3–7.4 pH interval and, at the same time, reaching a HCO3− concentration between 24 and 27 mmol dm−3, which are the normal concentrations reported for blood plasma. Mineralisation studies on calcium phosphate ceramics using this solution showed that, in the presence of such hydrogencarbonate concentrations, the formation of a mineralisation layer on the ceramic occurs via a carbonated octacalcium phosphate, that evolves to carbonated hydroxyapatite. The results suggest that mineralisation studies in this new carbonate-containing simulated inorganic plasma mimic biomineralisation more closely than traditional SBF.