Amorphous Calcium Phosphate Formation and Aggregation Process Revealed by Light Scattering Techniques

Abstract

Amorphous calcium phosphate (ACP) attracts attention as a precursor of crystalline calcium phosphates (CaPs) formation in vitro and in vivo as well as due to its excellent biological properties. Its formation can be considered to be an aggregation process. Although aggregation of ACP is of interest for both gaining a fundamental understanding of biominerals formation and in the synthesis of novel materials, it has still not been investigated in detail. In this work, the ACP aggregation was followed by two widely applied techniques suitable for following nanoparticles aggregation in general: dynamic light scattering (DLS) and laser diffraction (LD). In addition, the ACP formation was followed by potentiometric measurements and formed precipitates were characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results showed that aggregation of ACP particles is a process which from the earliest stages simultaneously takes place at wide length scales, from nanometers to micrometers, leading to a highly polydisperse precipitation system, with polydispersity and vol. % of larger aggregates increasing with concentration. Obtained results provide insight into developing a way of regulating ACP and consequently CaP formation by controlling aggregation on the scale of interest.

Comparison of the Effect of the Amino Acids on Spontaneous Formation and Transformation of Calcium Phosphates

“…Therefore the reaction progress can be followed by monitoring the pH changes in the system of interest [33,[43][44][45][46]. Typically, sigmoidal pH vs. time curves are obtained, in which [33,[43][44][45][46][47]: − In the initial precipitation stage (stage I), slight or negligible pH changes are observed, which correspond to the formation of ACP; − A subsequent rapid decrease in pH (stage II) is associated with secondary precipitation of crystalline phase upon the formation of ACP; − A final slight pH change (stage III) corresponds to the solution-mediated crystal growth and phase transformation of the crystalline phase formed in stage II.…”

Atomic force microscopy of food assembly: Structural and mechanical insights at the nanoscale and potential opportunities from other fields

“…Carrageenans, locust bean gum, guar gum, gellan gum, gum arabic, xanthan or pectin fibrous structures were also investigated (Funami, 2010;Gunning & Morris, 2018;Ikeda, Funami, & Zhang, 2005;Liu & Wang, 2011;Wang & Somasundaran, 2007). Crystalline structures of lactose (Dincer, Ogden, & Parkinson, 2014;Gao et al, 2017;Perkins et al, 2007), of saccharose (Masterson & Cao, 2008;Middendorf et al, 2016Middendorf et al, , 2018 or of calcium phosphate assemblies (Li, Wang, & Putnis, 2018;Wang, Lu, Xu, & Zhang, 2011;Čadež et al, 2018) are also accessible using AFM imaging.…”

Critical and diverse roles of phosphates in human bone formation

“…4C), which further aggregate into chains prior to transforming toward a more stable phase. [36][37][38][39] In the late 1990s, it was proposed that crystalline HA forms via the step-wise assembly of Posner's clusters. 34 However, speculation over the exact chemical composition of physiologically derived clusters and the applicability of this model for in vivo biomineral formation has only driven further efforts to understand the chemical structure of these early orthophosphate building blocks.…”