Calcium phosphates with apatitic structure (or apatites) constitute the mineral part of hard tissues in vertebrates. The structure and properties of apatites open several possibilities in medical sciences and also play an important role in living organisms for biomineralization processes. One of the most interesting characteristics of apatitic calcium phosphate is its surface reactivity and capability to exchange mineral ions and small molecules upon interaction with surrounding fluids. Such surface properties can be exploited and tailored in materials science to obtain nanostructured and bioactive biomaterials, in particular in view of drug delivery and tissue engineering.
In this chapter, biogenic calcium phosphates will be first presented, giving details about the principal characteristics of bone, tooth and pathological calcifications where calcium phosphates are present. We will then expose a general presentation of calcium phosphates used as biomaterials, especially in terms of ceramics, cements and coatings. Then the surface chemistry of synthetic and biogenic calcium phosphates will be examined in detail, summarizing the principal surface characteristics of biomimetic nanocrystalline apatites and of some other calcium phosphates of biological interest. In a subsequent part of the chapter, we will discuss surface interaction processes between calcium phosphate and molecules of biological interest: on one hand in the case of biomolecules (including peptides and proteins) for biomaterials development and biomineralization aspects, and on the other hand in the case of bioactive molecules for specific applications in drug delivery. Finally, we will conclude this chapter by presenting some in vitro and in vivo results obtained on functionalized calcium phosphates with the aim to develop innovative drug delivery devices.