Cell walls hydroxyapatite

Ryan JA, Zhang P, Hesterberg DA, Chou J, Sayers DE (2001) Formation of chloropyromorphite in lead-contaminated soil amended with hydroxyapatite. Env Sci Tech 35 3798-3803 Sarret G, Manceau A, Spadini L, Roux JC, Hazemann JL, Soldo Y, Eybert-Berard L, Menthonnex JJ (1998) Structural determination of Zn and Pb binding sites in Penicillium chrysogenum cell wall by EXAFS spectroscopy. Env Sci Tech 32 1648-1655. 

The level of calcium in solution will depend upon the presence of precipitating anions, notably phosphate and carbonate. Calcium will precipitate as the phosphate to give hydroxyapatite, Caio(P04)6(OH)2, in bones and teeth, and as the phosphate or carbonate to give other structures, including small crystals, or non-crystalline deposits in cells. Small crystals of calcium carbonate, found in the inner ear of some animals, are responsible for the control of balance. Various calcified tissues result from the precipitation of calcium salts, such as hydroxyapatite in the calcification of the aortic wall, and the oxalate in various stones. 

Hydroxyapatite substituted with metabolic elements such as Sr, Mg and Zn were deposited by pulsed current ECD technique (Gopi et al., 2014). The coatings imparted sufficient corrosion resistance to the Ti alloy substrate and showed potential for suitable cell attachment and proliferation. Addition of single-walled carbon nanotubes (SWCTs) to electrochemically deposited hydroxyapatite increased the coating bond strength to 26 MPa, an improvement of about 70% over that of pure hydroxyapatite (Pei et al., 2014). 

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