Abstract:

BACKGROUND: Nano-hydroxyapatite particles agglomerate so easily that their polymer-based nanocomposites are inferior to cortical bones in mechanical properties.
OBJECTIVE: To prepare stable hydroxyapatite (HA) colloid by new methods.
METHODS: 38 mL calcium nitrate solution (0.05 mol/L) was mixed with an isovolumetric solution of 2-aminoethyl dihydrogen phosphate (ADP), 3-phosphonopropionic acid (CEPA) and L-O-phosphoserine (LOP), respectively. Thereafter, 7.5 mL triammonium phosphate solution (0.15 mol/L) was dropped into each of the mixtures followed by aging at 40 ℃ and 80 ℃ for 4 hours, respectively. The modified HAs (ADP-HA, CEPA-HA, LOP-HA) were purified through centrifugation and water washing, followed by freeze drying.
RESULTS AND CONCLUSION: The as-synthesized products were still HA as proved by Fourier transform infrared spectroscopy and X-ray diffraction analyses, with some modifiers on surface. Zeta potentials showed that the CEPA-HA and LOP-HA were negatively charged while the ADP-HA was positively charged. The CEPA-HA and LOP-HA were re-suspended in water through 4-hour ultrasonication, forming light blue colloids with short-term (3 days) stability at pH 11. The ADP-HA suspension possessed slightly higher stability in acidic solution than that in neutral one, similar to the case in alkaline solution. But its stability in all cases (< 3 hours) was far from an ideal one. Creative methods should be under way to improve HA hydrocolloids’ stability.