Preparation, characterization and protein adsorption properties of nanostructured magnesium whitlockite

This article presents the preparation and characterization of various calcium-magnesium phosphate suspensions with particular focus on nanostructured magnesium whitlockite as potential protein adsorbent. The phosphates were synthesized by precipitation from mixed Ca(II)/Mg(II) solutions with disodium hydrogen phosphate followed by thermal treatment at 95 or 115 °C for 1 or 3 h. Structural characterization was performed by means of transmission electron microscopy with elemental and electron diffraction analysis, X-ray powder diffraction and infrared spectroscopy. It was found that nanocrystalline magnesium whitlockite was obtained at initial Ca/Mg molar ratio from 65/35 up to 85/15. The crystallite sizes of magnesium whitlockite were estimated from X-ray diffraction and were found to vary from 5 to 45 nm depending on the heating temperature and time at constant Ca/Mg initial molar ratio of 75/25. The nanocrystalline magnesium whitlockite samples exhibited a relatively high protein adsorption capacity, which is an important prerequisite for applications in protein delivery.