EDTA and NTA Effectively Tune the Mineralization of Calcium Phosphate from Bulk Aqueous Solution.

Doreen Hentrich,Montserrat Espanol,Klaus Tauer,Andreas Taubert,Maria-Pau Ginebra

doi:10.3390/biomimetics2040024

Abstract

This study describes the effects of nitrilotriacetic acid (NTA) and ethylenediaminotetraacetic acid (EDTA) on the mineralization of calcium phosphate from bulk aqueous solution. Mineralization was performed between pH 6 and 9 and with NTA or EDTA concentrations of 0, 5, 10, and 15 mM. X-ray diffraction and infrared spectroscopy show that at low pH, mainly brushite precipitates and at higher pH, mostly hydroxyapatite forms. Both additives alter the morphology of the precipitates. Without additive, brushite precipitates as large plates. With NTA, the morphology changes to an unusual rod-like shape. With EDTA, the edges of the particles are rounded and disk-like particles form. Conductivity and pH measurements suggest that the final products form through several intermediate steps.

Highlights

The increasing age of the world population leads to an increasing demand for materials for hard tissue repair
The current study evaluates the effects of two low molecular weight additives, nitrilotriacetic acid (NTA) and ethylenediaminotetraacetic acid (EDTA), on calcium phosphate (CP) mineralization from bulk aqueous solution under mild conditions
Calcium phosphate mineralization was performed in bulk solution between pH 5 and 9 in the presence (5, 10, and 15 mM) and in the absence (0 mM) of NTA over 4 h

Summary

Introduction

The increasing age of the world population leads to an increasing demand for materials for hard tissue repair. Many of these materials are based on calcium phosphate (CP) [1,2,3,4,5] and, for a biomaterial to work properly, it is necessary to tune and tailor synthetic CP-based biomaterials for a specific (medical) application. It is necessary to understand and control CP mineralization during synthesis. The resulting synthetic materials are similar to natural hard tissue [6,7] or precursors to biological minerals [8,9]. The crystal phase, crystal morphology, and crystal size of synthetic CP precipitates can be influenced by additives [7,8,9,10,11] such as polymers [12,13,14,15,16,17,18,19,20], surfactants [21], amino acids [22], poly(amino) acids [20,23,24,25,26,27,28,29,30,31,32,33], or poly(cations) [32,34,35,36,37,38,39,40,41].

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Discussion

Conclusion