Issue 3, 2016

High biocompatibility and improved osteogenic potential of amorphous calcium carbonate/vaterite

Abstract

In human bone, amorphous calcium carbonate (ACC) is formed as a precursor of the crystalline carbonated apatite/hydroxyapatite (HA). Here we describe that the metastable ACC phase can be stabilized by inorganic polyphosphate (polyP) that is also used as a phosphate source for the non-enzymatic carbonate/phosphate exchange during HA formation. This polymer was found to suppress the transformation of ACC into crystalline CaCO3 at a percentage of 5% [w/w] (“CCP5”) with respect to CaCO3 and almost completely at 10% [w/w] (“CCP10”). Both preparations (CaCO3/polyP) are amorphous, but also contain small amounts of vaterite, as revealed by XRD, FTIR and SEM analyses. They did not affect the growth/viability of SaOS-2 cells. Cell culture and Ca2+ release experiments revealed that the CaCO3 particles formed in the presence of polyP (CaCO3/polyP) are degradable and, unlike calcite, become disintegrated with time during the cell culture incubation. Again in contrast to calcite, “CCP5” and “CCP10” were found to exhibit osteogenic activity and induce the expression of alkaline phosphatase gene in SaOS-2 cells as well as in human mesenchymal stem cells (MSC). In vivo studies in rats, using PLGA microspheres inserted in the muscles of the back of the animals, revealed that the encapsulated “CCP10” is not only biocompatible but also supports the regeneration at the implant region. We conclude that ACC containing small amounts of vaterite has osteogenic potential and offers superior properties compared to the biologically inert calcite with respect to a potential application as a scaffold material for bone implants.

Graphical abstract: High biocompatibility and improved osteogenic potential of amorphous calcium carbonate/vaterite

Article information

Article type
Paper
Submitted
25 10 2015
Accepted
20 11 2015
First published
23 11 2015
This article is Open Access
Creative Commons BY license

J. Mater. Chem. B, 2016,4, 376-386

Author version available

High biocompatibility and improved osteogenic potential of amorphous calcium carbonate/vaterite

E. Tolba, W. E. G. Müller, B. M. Abd El-Hady, M. Neufurth, F. Wurm, S. Wang, H. C. Schröder and X. Wang, J. Mater. Chem. B, 2016, 4, 376 DOI: 10.1039/C5TB02228B

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