Crystallization of smooth amorphous calcium phosphate microspheres to core-shell hydroxyapatite microspheres

Area of Science:

• Biomineralization
• Materials Science
• Crystallography

Background:

• Calcium phosphates (Ca-P) are vital biological minerals in hard tissues.
• Controlling Ca-P crystallization is key for advanced material functionality.
• The amorphous calcium phosphate (ACP) to hydroxyapatite (HA) transformation mechanism remains unclear.

Purpose of the Study:

• To elucidate the crystallization mechanism of amorphous calcium phosphate (ACP) to hydroxyapatite (HA).
• To investigate the kinetics and underlying mechanisms of ACP microsphere transformation.
• To synthesize pure HA microspheres with a core-shell structure.

Main Methods:

• Hydrothermal treatment of amorphous calcium phosphate (ACP) microspheres.
• Utilizing sodium trimetaphosphate and l-glutamic during synthesis.
• Analysis of ACP to HA phase transformation using microscopy and kinetic studies.

Main Results:

• Pure hydroxyapatite (HA) microspheres with core-shell structures were successfully synthesized.
• The transformation proceeds via dissolution and re-crystallization of ACP.
• Crystallization advances through nanometre-sized clusters and directional arrangement of nanocrystalline whiskers.

Conclusions:

• The study reveals a detailed mechanism for HA crystal genesis from ACP precursors.
• Hydrothermal treatment time and additives influence the transformation kinetics.
• Findings provide crucial insights into hydroxyapatite formation under specific synthesis conditions.