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

Vida Čadež,Maja Sikirić,Ina Erceg,Darija Domazet Jurašin,Suzana Šegota,Daniel Lyons,Atiđa Selmani,Damir Kralj

doi:10.3390/cryst8060254

Vida Čadež, Maja Sikirić + Show 6 more

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https://doi.org/10.3390/cryst8060254

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Journal: Crystals	Publication Date: Jun 17, 2018
Citations: 24	License type: CC BY 4.0

Affiliation: Rudjer Boskovic Institute

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.

Highlights

Biomineralization, the process of hard tissue formation in living organisms, continues to be a source of inspiration for materials scientists
Calcium concentrations are small or absent; An abrupt decrease in pH associated with the secondary precipitation of crystalline phase upon amorphous calcium phosphate (ACP); Final slight pH change associated with solution-mediated growth and phase transformation
In the systems that were mechanically stirred, an additional initial stage was observed in which a significant decrease of pH was observed, pointing to a possible difference in the mechanisms of ACP

Summary

Introduction

Biomineralization, the process of hard tissue formation in living organisms, continues to be a source of inspiration for materials scientists. The inspiration derives from the fact that biominerals have excellent properties, which to a great degree are still not matched by any man-made materials. They are formed in an economical way at low temperatures and pressures, thereby inspiring novel routes of green synthesis [1]. Amorphous calcium phosphate (ACP) attracts special attention as it is a precursor in the formation of vertebrates’ hard tissue [3,4,5,6,7,8]

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