Amorphous Calcium Phosphate and Amorphous Calcium Phosphate Carboxylate: Synthesis and Characterization

Amorphous calcium phosphate (ACP) is the first solidphase precipitatedfrom a supersaturated calcium phosphate solution. Naturally, ACP isformed during the initial stages of biomineralization and stabilizedby an organic compound. Carboxylic groups containing organic compoundsare known to regulate the nucleation and crystallization of hydroxyapatite.Therefore, from a biomimetic point of view, the synthesis of carboxylateions containing ACP (ACPC) is valuable. Usually, ACP is synthesizedwith fewer steps than ACPC. The precipitation reaction of ACP is rapidand influenced by pH, temperature, precursor concentration, stirringconditions, and reaction time. Due to phosphates triprotic nature,controlling pH in a multistep approach becomes tedious. Here, we developeda new ACP and ACPC synthesis approach and thoroughly characterizedthe obtained materials. Results from vibration spectroscopy, nuclearmagnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS),true density, specific surface area, and ion release studies haveshown a difference in the physiochemical properties of the ACP andACPC. Additionally, the effect of a carboxylic ion type on the physiochemicalproperties of ACPC was characterized. All of the ACPs and ACPCs weresynthesized in sterile conditions, and in vitro analysis was performedusing MC-3T3E1 cells, revealing the cytocompatibility of the synthesizedACPs and ACPCs, of which the ACPC synthesized with citrate showedthe highest cell viability.