Synthetic amorphous calcium phosphate and its relation to bone mineral structure

Hierarchical self-assembly of amelogenin and the regulation of biomineralization at the nanoscale

“…The average size of these nanoparticles after defocus correction was 9.2 Å (SD ¼ 2.2 Å, N ¼ 55) similar to the prenucleation clusters which were recently demonstrated by Sommerdijk and coworkers in a calcium phosphate mineralization system using cryo-EM (22,23). The idea of roughly spherical clusters, 9.5 Å in diameter, with the chemical formula of Ca 9 ðPO 4 Þ 6 was originally proposed by Posner and Betts in the 1970s based upon their studies of calcium phosphate mineralization using the X-ray radial distribution method (24). These clusters, often identified as Posner clusters, are thought to be building blocks of both amorphous calcium phosphate as well as apatitic mineral phases (24,25), which is of particular importance for biomineralization systems where metastable amorphous phases often serve as precursors to crystalline minerals (26,27).…”

“…The idea of roughly spherical clusters, 9.5 Å in diameter, with the chemical formula of Ca 9 ðPO 4 Þ 6 was originally proposed by Posner and Betts in the 1970s based upon their studies of calcium phosphate mineralization using the X-ray radial distribution method (24). These clusters, often identified as Posner clusters, are thought to be building blocks of both amorphous calcium phosphate as well as apatitic mineral phases (24,25), which is of particular importance for biomineralization systems where metastable amorphous phases often serve as precursors to crystalline minerals (26,27). After 10 min in the presence of rM179, similar prenucleation clusters formed, which often assembled into small groups (Figs.…”

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…Generally, the ACP particles are smaller if prepared under conditions of high supersaturation and/or high pH, while for a given pH, higher temperatures give larger particles (Blumenthal et al 1972). The freshly precipitated ACPs contain 10-20 % by weight of tightly bound water, which is removed by vacuum drying at elevated temperature (Posner and Betts 1975). The amorphization degree of ACPs increases with the concentration increasing of Caand PO 4 -containing solutions, as well as at a high solution pH and a low crystallization temperature.…”

“…Due to this reason, hexagonal HA is seldom the stoichiometric phase and very rare single crystals of natural HA always exhibit the hexagonal space group. The detailed description of the HA structure was first reported in 1964 (Kay et al 1964) and its interpretation in terms of aggregation of Ca 9 (PO 4 ) 6 clusters, the so-called Posner's clusters, has been widely used since publication of the article by Posner and Betts (Posner and Betts 1975).…”

Ion-association complexes unite classical and non-classical theories for the biomimetic nucleation of calcium phosphate

“…Already in the 1960s, biomimetic mineralization experiments were directed at understanding the formation mechanism of this mineral, and resulted in the precipitation of calcium phosphate with X-ray diffraction characteristics identical to those of the biological material 11 . These early investigations indicated the presence of a metastable amorphous precursor phase, which was postulated to consist Ca 9 (PO 4 ) 6 clusters 12 . Although initially these observations were met with skepticism 13 , recently reports confirmed that the precipitation of calcium phosphate indeed involves the formation of nanometre-sized building blocks [14][15][16][17][18] .…”