Biomedical Engineering Reference
In-Depth Information
Figure 1.17
A schematic representation of the different stages of a surface-
directed mineralization of calcium orthophosphates. In stage
1, aggregates of pre-nucleation clusters are in equilibrium with
ions in solution. The clusters approach a surface with chemical
functionality. In stage 2, pre-nucleation clusters aggregate near
the surface, with loose aggregates still in solution. In stage 3,
further aggregation causes densification near the surface. In
stage 4, nucleation of spherical particles of ACP occurs at the
surface only. In stage 5, crystallization occurs in the region of
the ACP particles directed by the surface. reprinted from refs.
[656, 850] with permission.
To conclude this part, it is worth reminding that calcium
orthophosphates of biological origin are sparingly soluble in aqueous
solutions. Removing them from the places of unwanted deposition
would be an equivalent of bone demineralization; that is a challenge.
Therefore, the majority of therapeutic approaches are directed at
preventing the progression of pathological calcifications. Among
them, a chelation therapy might be of some interest to chemists and
materials researchers because it deals with chemical processes [851,
852]. The general principles of demineralization and decalcification
(i.e., removing the mineral Ca-containing compounds (phosphates
and carbonates) from the bioorganic matrix) have been extensively
reviewed [853, 854], where the interested readers are referred to.
1.6
Biomimetic Crystallization of Calcium
Orthophosphates
The term “biomimetics” (“the mimicry of life”) was coined by an
American inventor, engineer and biophysicist Otto Herbert Schmitt
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