Selective protein adsorption property and structure of "nano- crystalline hydroxy-carbonate apatite

The selective protein adsorption property and the local structure around carbonate ions of nanocrystalline hydroxy-carbonate apatite were examined in this study. Considerable change in the selectivity in the adsorption of BSA and β₂-MG was observed due to the incorporation of the carbonate ions in hydroxyapatite lattice. Since the protein adsorption property seems to be related to the surface charge density of hydroxyapatite due to the carbonation, the chemical states of the incorporated carbonate ions were examined by the ³¹C CP-MAS NMR spectroscopy. At least four peaks assignable to carbonate ions in A-site(OH^-) and B-site(PO ₄^3-) were observed in ¹³C CP-MAS NMR spectrum. Thus, we must take into consideration that the surface charge distribution and the decrement of polar groups such as OH^- groups due to the distribution of carbonate ions in both A- and B-sites of the hydroxyapatite lattice are particularly favorable for β₂-MG adsorption rather than for BSA adsorption.