Hydroxyapatite synthetic

Hydroxyapatite, Ca2Q(PO (OH)2, may be regarded as the parent member of a whole series of stmcturaHy related calcium phosphates that can be represented by the formula M2q(ZO X2, where M is a metal or H O" Z is P, As, Si, Ga, S, or Cr and X is OH, F, Cl, Br, 1/2 CO, etc. The apatite compounds all exhibit the same type of hexagonal crystal stmcture. Included are a series of naturally occurring minerals, synthetic salts, and precipitated hydroxyapatites. Highly substituted apatites such as FrancoHte, Ca2Q(PO (C02) (F,0H)2, are the principal component of phosphate rock used for the production of both wet-process and furnace-process phosphoric acid. 

Fig. 12.3 Powder X-ray diffraction patterns of biological and synthetic hydroxyapatites.

It was obvious to early researchers on synthetic bone material that a pure calcium phosphate bioceramic would be the optimum replacement for human and mammalian bone. The calcium phosphate in human bone is called hydroxyapatite (Fig. 1). It is an ionic substance having the formula Ca5(0H)(P04)3. 

Sutter B, Taylor RE, Hossner LR, Ming DW. Solid state 31phosporous nuclear magnetic resonance of iron-, manganese-, and copper-containing synthetic hydroxyapatites. Soil Sci. Soc. Am. I. 2002 66 455 463. 

Rehman, I., Smith, R., Flench, L. L., and Bonfield, W. (1995). Structural evaluation of human and sheep bone and comparison with synthetic hydroxyapatite by FT-Raman spectroscopy. Journal of Biomedical Materials Research 29 1287-1294. 

Synthetic hydroxyapatite prepared by mixing stoichiometric amounts of aqueous solutions of calcium nitrate and ammonium phosphate was used in this study. The pH of the boiling suspension was maintained at about 10 by flowing a mixture of NH and throughout the precipitation process. The precipitate was repeatedly washed until the conductivity of the supernatant liquid was observed to be constant. The washed sample was freeze-dried and analyzed. An elemental analysis of the batch preparation showed the Ca/P molar to be ratio 1.64, with the predominant impurity being 2... 

The bisphosphonates are synthetic organic compounds that are incorporated directly into the hydroxyapatite of bone and then inhibit osteoclastic bone resorption. This antiresorptive action makes them useful in the pharmacological treatment of hypercalcemia, osteoporosis, and Paget s disease. 

R.Z. Legeros, Biological and synthetic apatites, in P.W. Brown, B. Constantz (Eds.), Hydroxyapatite and Related Materials, CRC Press, Boca Raton, 1994, pp. 3-28. 

This luminescence center is not detected in minerals yet, but is well known in synthetic phosphors, for example in halophosphates, which are closely related to hydroxyapatite (Blasse and Grabmaier 1994). The Sb doped calcium halophosphate is a very efficient blue-emitting phosphor under short wave 254 excitation (Fig. 5.56). When the halophosphate host lattice contains not only Sb, but also Mn, part of the energy absorbed by the Sb ions is transferred to Mn ", which shows an orange emission. By carefully adjusting the... 

Bisphosphonates. Bisphosphonates are synthetic compounds designed to function as mimics of pyrophosphate, in which the oxygen atom in P-O-P is replaced with a carbon atom, creating a non-hydrolyzable backbone structure. The bisphosphonates selectively bind to the hydroxyapatite portion of the bone, decreasing the number of sites along the bone surface at which osteoclast-mediated bone resorption can occur. This permits the osteoblasts to lay down well-mineralized new bone without competition from osteoclasts. Clinically employed bisphosphonates include etidronate (8.109), tilu-dronate (8.110), risedronate (8.111), alendronate (8.112), and pamidronate (8.113). 

Valsami-Jones et al. (1998) conducted similar studies with a synthetic, microcrystalline hydroxyapatite in either a Pb or Cd buffered solution. Using AFM, hydroxypyromorphite was observed to grow epitaxially on the hydroxyapatite surface in a clear example of heterogeneous nucleation. Cd removal differed, with the likely formation of a Ca-Cd phosphate solid solution. 

Lazic, S. Vukovic, Z. 1991. Ion exchange of strontium on synthetic hydroxyapatite. Journal of Radioanalytical and Nuclear Chemistry, 149, 161-168. ... 

Lusvardi, G., Malavasi, G., Menabue, L. Saladini, M. 2002. Removal of cadmium ion by means of synthetic hydroxyapatite. Waste Management, 22, 853-857. 

Suzuki, T., Hatsushika, T. Hayakawa, Y. 1981. Synthetic hydroxyapatites as inorganic cation-exchangers. Journal of the Chemical Society Faraday Transactions, 77, 1059-1062. 

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