Next Article in Journal
Depression Mechanism of Strontium Ions in Bastnaesite Flotation with Salicylhydroxamic Acid as Collector
Next Article in Special Issue
Structural Transition of Inorganic Silica–Carbonate Composites Towards Curved Lifelike Morphologies
Previous Article in Journal
Mobility and Attenuation Dynamics of Potentially Toxic Chemical Species at an Abandoned Copper Mine Tailings Dump
Previous Article in Special Issue
Liquid Cell Transmission Electron Microscopy and the Impact of Confinement on the Precipitation from Supersaturated Solutions
Article Menu
Issue 2 (February) cover image

Export Article

Open AccessArticle

Pyrophosphate-Inhibition of Apatite Formation Studied by In Situ X-Ray Diffraction

Department of Chemistry and iNANO, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark
Author to whom correspondence should be addressed.
Minerals 2018, 8(2), 65;
Received: 28 August 2017 / Revised: 10 February 2018 / Accepted: 12 February 2018 / Published: 13 February 2018
PDF [2769 KB, uploaded 13 February 2018]


The pathways to crystals are still under debate, especially for materials relevant to biomineralization, such as calcium phosphate apatite known from bone and teeth. Pyrophosphate is widely used in biology to control apatite formation since it is a potent inhibitor of apatite crystallization. The impacts of pyrophosphate on apatite formation and crystallization kinetics are, however, not fully understood. Therefore, we studied apatite crystallization in water by synchrotron in situ X-ray diffraction. Crystallization was conducted from calcium chloride (0.2 M) and sodium phosphate (0.12 M) at pH 12 where hydrogen phosphate is the dominant phosphate species and at 60 °C to allow the synchrotron measurements to be conducted in a timely fashion. Following the formation of an initial amorphous phase, needle shaped crystals formed that had an octacalcium phosphate-like composition, but were too small to display the full 3D periodic structure of octacalcium phosphate. At later growth stages the crystals became apatitic, as revealed by changes in the lattice constant and calcium content. Pyrophosphate strongly inhibited nucleation of apatite and increased the onset of crystallization from minute to hour time scales. Pyrophosphate also reduced the rate of growth. Furthermore, when the pyrophosphate concentration exceeded ~1% of the calcium concentration, the resultant crystals had reduced size anisotropy suggesting that pyrophosphate interacts in a site-specific manner with the formation of apatite crystals. View Full-Text
Keywords: apatite; in situ X-ray diffraction; crystallization; nucleation; pyrophosphate; biomimetic materials apatite; in situ X-ray diffraction; crystallization; nucleation; pyrophosphate; biomimetic materials

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
Printed Edition Available!
A printed edition of this Special Issue is available here.

Share & Cite This Article

MDPI and ACS Style

Ibsen, C.J.S.; Birkedal, H. Pyrophosphate-Inhibition of Apatite Formation Studied by In Situ X-Ray Diffraction. Minerals 2018, 8, 65.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Minerals EISSN 2075-163X Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top