Hydroxyapatite, preparation

Chen, C.-W., Oakes, C.S., Byrappa, K., Riman, R.E., Brown, K., TenHuisen, K. S. and Janas, V.F. (2004) Synthesis, characterization, and dispersion properties of hydroxyapatite prepared by mechanochemical-hydrothermal... 

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... 

Monma. H., Ueno, S. and Kanazawa, T. (1981). Properties of hydroxyapatite prepared by the hydrolysis of tricalcium phosphate. J. Chem. Tech. Biotechnol., 31 15-24. 

Finally, sol-gel processing is widely used in the exploration of methods to prepare biomaterials for example, hydroxyapatite prepared from triethyl phosphite and calcium salts.237,238 Phosphate sol-gel synthesis is more difficult than for silicates since phosphoric esters are very difficult to hydrolyze 239... 

A. Nakahira, M, Tamai, H. Aritani, S. Nakamura, K. Yamasliita, biocompatibility of dense hydroxyapatite prepared using an SPS process," J Biomed Mater Res., 62 [4] 550-557 (2002). 

Chow, L.C., Sun, L., Hockey, B., 2004, Properties of nanostructured hydroxyapatite prepared by a spray drying technique, J. Res. Natl. Inst. Stan. Technol. 109, 11-12. 

Uematsu K, Takagi M, Honda T, Uchida N, Saito K (1989) Transparent hydroxyapatite prepared by hog isostatic pressing of filter cake. J Am Ceram Soc 72 1476-1478... 

Meejoo S., Maneeprakorn W., Winotai P. (2006). Phase and thermal stability of nanocrystalline hydroxyapatite prepared via microwave heating. Therntochimica Acta, No. 447, pp. 115-120... 

Huang, X., Miao, X., 2007. Novel porous hydroxyapatite prepared by combining H2O2 foaming with PU sponge and modified with PLGA and bioactive glass. Journal of Biomaterials Applications 21, 351-374. 

FIG. 2 Mass spectrometer temperature-programmed dehydration (MSTPD) spectra showing the evolution of water as a function of temperature from (1) hydroxyapatite precipitated from an aqueous solution via an amorphous precursor phase, (2) hydroxyapatite prepared in a hydrothermal bomb, and (3) apatite from a mineral source. (After Ref. 28.)... 

F. 2 SEM image of EPN based on bacterial cellulose-hydroxyapatite prepared by electrospinning at 25 kV a SOOOOx and b 60000x (adapted liom Saska and Barud 2011)... 

Other ways in which the Ca P ratio could be caused to depart from the ideal include (1) the presence of an additional crystalline compound, octacalcium phosphate, whose unit cell composition is Ca8(HP04)2(P04)4-5H20 and whose Ca P ratio is 1 3-3, giving rise to the possibility that biological mineral may be an intercrystalline mixture (2) substitution of other ions for calcium in the crystal lattice. For example, hydroxyapatites prepared by precipitation from solutions of different pH have different Ca P ratios. Substitution of hydronium ions for calcium ions causes a decrease in the Ca P ratio (3) adsorption of excess phosphate or calcium phosphate complexes on to the crystal surface. 

Y.W. Gua, KA. Khora, P. Cheang, Bone-like apatite layer formation on hydroxyapatite prepared by spark plasma sintering (SPS), Biomaterials 25 (2004) 4127-4134. 

Tricalcium phosphate, Ca2(P0 2> is formed under high temperatures and is unstable toward reaction with moisture below 100°C. The high temperature mineral whidockite [64418-26-4] although often described as P-tricalcium phosphate, is not pure. Whidockite contains small amounts of iron and magnesium. Commercial tricalcium phosphate prepared by the reaction of phosphoric acid and a hydrated lime slurry consists of amorphous or poody crystalline basic calcium phosphates close to the hydroxyapatite composition and has a Ca/P ratio of approximately 3 2. Because this mole ratio can vary widely (1.3—2.0), free lime, calcium hydroxide, and dicalcium phosphate may be present in variable proportion. The highly insoluble basic calcium phosphates precipitate as fine particles, mosdy less than a few micrometers in diameter. The surface area of precipitated hydroxyapatite is approximately... 

In this work, simple (single-use) biosensors with a layer double stranded (ds) calf thymus DNA attached to the surface of screen-printed carbon electrode assembly have been prepared. The sensor efficiency was significantly improved using nanostructured films like carbon nanotubes, hydroxyapatite and montmorillonite in the polyvinylalcohol matrix. 

Results are different when solutions are used instead of suspensions. Chitosan-hydroxyapatite composites with a homogeneous nanostructure have been prepared by a coprecipitation method by Yamaguchi et al. [170]. 

Chitosan scaffolds were reinforced with beta-tricalciiun phosphate and calcium phosphate invert glass [177]. Along the same line, composites of Loligo beta-chitin with octacalcium phosphate or hydroxyapatite were prepared by precipitation of the mineral into a chitin scaffold by means of a double diffusion system. The octacalciiun phosphate crystals with the usual form of 001 blades grew inside chitin layers preferentially oriented with the 100 faces parallel to the surface of the squid pen and were more stable to hy-... 

Aryal, S., Bahadour, K.C.R., Bhattarai, J.R., Prabu, P. and Kim, H.Y. (2006) Immobilization of collagen on gold nanoparticles, preparation, characterization and hydroxyapatite growth, foumal of Materials Chemistry, 16, 4642-4648. 

SBF is a solution that has inorganic ion concentrations similar to those of human blood plasma but does not contain any cells or protein. A brief summary of SBF, introduced by Cho et al. [17], follows. The ion concentrations of SBF are given in Table 11.1 [17]. The pH of SBF is typically adjusted to 7.25 or 7.40 at 36.5 °C. This fluid is a metastable solution containing calcium and phosphate ions supersaturated with respect to hydroxyapatite. SBF is prepared by successively dissolving the reagent-grade chemicals in ultra-pure water in the order given in Table 11.2 [17]. Each new chemical is added after the previous one has completely dissolved. The temperature... 

Miyazaki et al. [43] reported that a sol-gel-derived Ta2Os gel shows hydroxyapatite-forming ability in SBF even in the amorphous state. Therefore, PTM0-Ta205 nano-hybrids prepared by a sol-gel method can be expected to form hydroxyapatite in SBF without any treatment. PTMO-CaO-Ta2Os nano-hybrids were prepared by... 

Fig. 11.22 Preparation of hydroxyapatite-laminine nano-hybrid layer.

Hydroxyapatite is prepared by mixing a solution of sodium phosphate (Na2HP04) with calcium chloride (CaCl2). A white precipitate known as brushite is formed. Brushite is then converted to hydroxyapatite by heating to 100°C in the presence of ammonia ... 

Hydroxyapatite particles can be used for radiation synovectomy by exploiting the strong binding of rhenium diphosphonate complexes to the surface of hydroxyapatite (vide supra). The same 186Re-HEDP preparations as for bone palliative therapy are used. When injected into joints, these particles (mean diameter 25 pm, maximum diameter 45 pm) remain within the joint to the extent of at least 95% for several days in arthritic rabbits and rats [156], More recently, microspheres have been labeled with 188Re for this purpose [156a,b],... 

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