Chemistry of Calcium Phosphates

Since calcium oxide is more than sparsely soluble and its reaction with phosphoric acid or a soluble phosphate is highly exothermic, researchers have used less soluble salts of calcium to react with the phosphates and form a phosphate ceramic [4-12]. In the acidic medium of the phosphate solutions, the salts of calcium dissolve slowly and release Ca (aq) into the solution, which subsequently reacts with phosphate anions and forms calcium phosphates. The best calcium minerals for forming CBPCs are combination of oxides of calcium and insoluble oxides such as silica or alumina, e.g., calcium silicate (CaSi03) and calcium aluminate (CaAl204), or even a phosphate of calcium such as tetracalcium phosphate (Ca4(P04)2 0). These minerals are reacted with acid phosphate salts to form phosphate cements. 

Stability regions of ionic species of calcium silicate and aluminates. 

Dissolved Aqueous Phases Dissolution Reaction and Ionic Concentration Equation No. pH Range 

Consider, for example, Eq. 13.1a. Following the notations of Chapters 4 and 5, we relate the concentrations of individual species and the net change in Gibbs free energy that occurs during the reaction by the following relation. We obtain from Eq. 13.1a, 

Equation 13.7 provides the ionic concentration (Ca (aq)) in the pH range of 0-10. One may follow a similar approach to derive the pH dependence of (Ca (aq)) for other pH regions. 

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In this chapter, after an overview of bone and mineral metabolism, we discuss the clinical chemistry of calcium, phosphate, and magnesium the hormones regulating these minerals the major disorders of bone and the clinical use of markers of bone formation and degradation. A goal of the chapter is to provide, in one place, a view of these highly interrelated topics. 

Lemons J.E., Bajpai P.K., Patka P, Bonel G., Starling L.B., Rosenstiel T., Muschler G, Kampnier S., and Timmermans T. 1988. Significance of the porosity and physical chemistry of calcium phosphate ceramics orthopaedic uses. In Bioceramics Material Characteristics Versus In Vivo Behavior. Annals of New York Academy of Sciences, Vol. 523, pp. 190-197. 

De Groot, K. Le Geros, R.(1988). Significance of Porosity and Physical Chemistry of Calcium Phosphate Ceramics. In Ducheyne, P. Lemons editors. Bioceramics Material Characteristics Versus In Vivo Behaviour. (268-277). New York Publ. J. Am. Acad. Sci. 

In an interesting fusion of biology and materials chemistry, the group of Tang [25] demonstrated that individual cells of yeast, Saccharomyces cerevisiae, can be covered in successive layers of calcium phosphate with the assistance of... 

Nancollas, G.H., Tomson, M.B., Battaglia, G., Wawrousek, H., and Zuckermann, M. Precipitation of calcium phosphate. The influence of tricarboxylic acid, magnesium, and phosphonate, in Rubin, A.J., "Chemistry of Wastewater Technology,",... 

Mineralization is the precipitation of calcium phosphate, but biochemical mediation of this process is not fully understood. In this chapter, the chemistry underlying mineralization (Sect. 1) and the structures ofbones and teeth (Sect. 2) are described. Osteoblasts secrete osteoid matrix and matrix vesicles that transport type I collagen and calcium phosphate, respectively, to the matrix where they will mineralize. Secreted matrix vesicles take up calcium and phosphate until they burst and release the calcium phosphate, which then redissolves and remineralizes around the type I collagen (Sect. 3). Glycoproteins involved in correctly modeling bone and dentin, and the role of osteocalcin in limiting excessive bone growth is then discussed (Sect. 4). There follows a detailed description of enamel (E) mineralization and of the major proteins involved (Sect. 5) followed by two summaries the difference between enamel and bone mineralization, and the vitamins required for mineralization (Sect. 6). 

Fig. 17 Schematic representation of ion-channel controlled precipitation of calcium phosphate in block copolymer vesicles (middle drawing), and TEM micrographs right drawing) of phosphate-loaded PMOXA-PDMS-PMOXA triblock copolymer giant vesicles after 1 and 24 h of incubation with CaCl2 solution in the presence of the ionophore scale bar. 500 nm [163]. Reproduced with permission of The Royal Society of Chemistry...

Nancollas, G.H. and Tomazic, B. (1974) Growth of calcium phosphate on hydroxyapatite crystals. Journal of Physical Chemistry, 78, 2218-2225. 

Calcium phosphates as chemical compoimds arise interest of the numerous fields of science, like geology, chemistry, biology and medicine. Many forms of calcium phosphates are... 

Sir John Bennett Lawes (1814-1900), a pupil of Daubeny in Oxford, was a small land-owner. He took out a patent in 1842 for the preparation of superphosphate of lime by the action of sulphuric acid on coprolites, apatite etc., and began manufacture in 1843 he sold the factories etc. in 1872, but continued to be interested in technical chemistry. John Stevens Henslow, professor of botany in Cambridge, found that coprolites contain 56 to 61 p.c. of calcium phosphate. Sir Joseph Henry Gilbert (1817-1901), a pupil of Liebig, after academic work, experimented on dyeing and calico-printing in the Manchester district and then joined Lawes in 1843. ... 

Biomineralization is the most glaring example of the misnomer of bioinorganic chemistry. It encompasses the formation of largely inorganic minerals by the processes of life. Examples of biomineralization are the formation of calcium phosphate to create bones for structure, calcium carbonate as protective shells, iron oxide to store iron in animal cells, and the formation of magnetite as orientational materials in magnetobacterial cells (Table III). All of these examples demonstrate the precise control of mineral size, structure, shape, orientation, and organization that chemists strive for in the development of novel methods for material syntheses. 

De Groot, K., Klein, C.P.A.T., Wolke, J.G.C. De Bliek-Hogervorst, J. (1990). Chemistry of ealeium phosphate bioceramics. In Yamamuro, T., Hech, L.L. Wilson, J., Editors. Handbook of Bioactive Ceramics, Vol. 11, Calcium phosphate and hydroxylapatite Ceramics (3-15). Boca Raton, FL.CRC Press. 

Alqap, AS.F., Sopyan, L(2009) Low temperature hydrothermal synthesis of calcium phosphate ceramics effect of excess Ca precursor on j ase behaviour. Indian Journal of Chemistry 48A 1492-1500. 

Bohner, M. (2007) Reactivity of calcium phosphate cements. Journal of Materials Chemistry, 17, 3980-6. 

Fowler, E., li, M., Mann, S. and Margohs, H.C. (2005) Influence of surfactant assembly on the formation of calcium phosphate materials a model for dental enamel formation. Journal of Materials Chemistry, 15, 3317-... 

Some acrylic acid copolymers are promoted as having a very wide range of functions that permit them to act as calcium phosphate DCAs, barium sulfate antiprecipitants, particulate iron oxides dispersants, and colloidal iron stabilizers. One such popular copolymer is acrylic acid/sulfonic acid (or acrylic acid/ 2-acrylamido-methylpropane sulfonic acid, AA/SA, AA/AMPS). Examples of this chemistry include Acumer 2000 (4,500 MW) 2100 (11,000 MW) Belclene 400, Acrysol QR-1086, TRC -233, and Polycol 43. 

Besha, K., Key, C, Glimcher, M., Schimizu, M. and Griffin, R.G. 1990 Solid state carbon-13 and proton NMR studies of carbonate-containing calcium phosphates and enamel. Journal of Solid State Chemistry 84 71-81. 

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