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ABSTRACT
The apatites are a family of inorganic compounds. In particular, calcium phosphate apatites are of particular interest in the biomaterials field. This article focuses on nanocrystalline apatites that are, for example, present in bone and dentin, and for which synthetic analogs called “biomimetic apatites” can be prepared and used for biomedical applications. Various aspects are addressed concerning their specific characteristics, their physicochemical and thermodynamic properties, their preparation and processing, and their biomedical use mainly as bone substitutes, but also in nanomedicine, for diagnosis or for therapy.
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Read the articleAUTHORS
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Christophe DROUET: Doctor of Materials Science - CNRS Research Director, CIRIMAT Laboratory (Toulouse), France
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David GROSSIN: Doctorate in materials chemistry - Senior Lecturer at the Institut National Polytechnique de Toulouse, CIRIMAT Laboratory (Toulouse), France
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Christèle COMBES: Doctor of Materials Science - Professor at the Institut National Polytechnique de Toulouse, CIRIMAT Laboratory (Toulouse), France
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Stéphanie SARDA: Doctor of Materials Science - Senior Lecturer at Toulouse III Paul Sabatier University, CIRIMAT Laboratory (Toulouse), France
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Sophie CAZALBOU: Doctorate in Materials Science and Engineering - Senior Lecturer at Toulouse III Paul Sabatier University, CIRIMAT Laboratory (Toulouse), France
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Christian REY: Doctor of Physical Sciences - Professor Emeritus, Institut National Polytechnique de Toulouse, CIRIMAT Laboratory (Toulouse), France
INTRODUCTION
Nanocrystalline apatites are ceramic-like compounds found naturally in certain biominerals. It is also possible to synthesize biomimetic analogues (with characteristics close to those of biological apatites) under bio-inspired conditions. These compounds differ significantly from geological apatites or hydroxyapatite prepared at high temperature. Whether of biological or synthetic origin, nanocrystalline apatites have a number of specific characteristics: nanometric crystals, a substoichiometric chemical composition in terms of calcium and hydroxide ions, and containing divalent anions such as
and/or
, an elongated, generally platelet-like morphology, and their nanocrystals are made up of an apatitic core covered by a non-apatitic hydrated ionic layer containing particularly mobile ions. The presence of this surface layer gives nanocrystals exceptional reactivity, which can be used in ion exchange or molecular adsorption reactions (biomolecules, drugs, etc.) to confer additional properties to these compounds (antibacterial, anti-resorptive, luminescence, etc.). Nanocrystals are thermodynamically metastable and evolve progressively under moist conditions, enabling them to mimic more or less mature bone mineral. It is possible to shape these biomimetic apatites for a variety of biomedical applications, not only for bone regeneration but also in nanomedicine for medical diagnostics or cell therapy. But the shaping techniques used, including sintering operations, must take account of this metastable character, by implementing "low-temperature" approaches, for example. Similarly, the physico-chemical characterization of these compounds must be carried out with care, to avoid altering the nanocrystals during analysis.
Fields of expertise. Biomaterials. Biomimetics. Nanomedicine. Biominerals. Calcium phosphates
Degree of technology diffusion. Maturity
Technologies involved. Synthesis of biomimetic...
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KEYWORDS
bone mineral | synthetic analog | hydrated layer | calcium phosphate
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Biomimetic apatites
Apatites in biominerals
Bibliography
Standards and norms
- Surgical implants – Hydroxyapatite – Part 2: Hydroxyapatite coatings - ISO 13779-2 - 2008
- Surgical implants – Hydroxyapatite – Part 3: Chemical analysis and characterization of crystallinity and phase purity - ISO 13779-3 - 2008
- Surgical implants – Hydroxyapatite – Part 4: Determination of coating adhesion resistance - ISO 13779-4 - 2002
- Surgical implants – Hydroxyapatite – Part 6: powders...
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