Hydroxyapatite formation

Hydroxyapatite formation on/in poly(vinyl alcohol) hydrogel matrices using an alternate soaking process. Chemistry Letters, 27, 711—712. 

Taguchi, T., Shiraogawa, M., Kishida, A. and Akashi, M. (1999) A study on hydroxyapatite formation on/in the hydroxyl groups-bearing nonionic hydrogels. Journal of Biomaterials Science-Polymer Edition, 10, 19-32. 

Watanabe, J. and Akashi, M. (2006) Novel biomineralization for hydrogels electrophoresis approach accelerates hydroxyapatite formation in hydrogels. Biomacromolecules, 7, 3008-3011. 

Kokubo et al. [16,17] showed that the hydroxyapatite formation on the surfaces of bioactive materials in the living body can be reproduced even in an acellular protein-free simulated body fluid (SB F) with ion concentrations nearly equal to those of human blood plasma. This indicates that the hydroxyapatite layer is formed through chemical reaction of the bioactive glass with the surrounding body fluids. The formed layer consists of carbonated hydroxyapatite with small crystallites and low crystallinity, which is similar to bone hydroxyapatite. Hence the bioactivity of a material can be evaluated even in vitro by examining the hydroxyapatite formation on its surface in SBF. 

Human body fluid and SBF contain calcium and phosphate ions that are already supersaturated with respect to hydroxyapatite [20]. However, these fluids do not spontaneously deposit hydroxyapatite under normal conditions. This is because the activation energy barrier for hydroxyapatite nudeation is very high. Therefore, the ability of substrates to induce heterogeneous nudeation of hydroxyapatite and the degree of supersaturation of SBF with respect to hydroxyapatite are important factors for hydroxyapatite formation on materials in the body fluid and SBF. 

Ohtsuki et al. [22] assumed the hydroxyapatite formation mechanism to be as follows. The formation of the hydroxyapatite layer is triggered by release of Ca2+ ions... 

Fig. 11.3 Compositional dependence of hydroxyapatite formation on the glasses in the system Ca0-Si02-P205. Soaking period ...

Boskey, A., Posner, A, S. The role of synthetic and bone extracted Ca-Phospholipid-PC>4 complexes in hydroxyapatite formation. Calc. Tiss. Res. 23, 251 (1977)... 

Francis, M. D., and Webb, N. C. Hydroxyapatite formation from a hydrated calcium monohydrogen phosphate precursor. Calc. Tiss. Res. 6, 335-342 (1971). 

Golomb G, Schlossman A, Saadeh H, Levi M, Van Gelder JM, Breuer E. Bisacylphosphonates inhibit hydroxyapatite formation and dissolution in vitro and dystrophic calcification in vivo. Pharm. Res., 1992, 9, 143-148. 

H]o.8[(OCH2CH2)20Me]i.2 n were allowed to react with Si(OEt)4 under hydrolytic conditions.The rate of hydroxyapatite formation from CaHP04.2H20 and Ca4(P04)20 in aqueous solution is influenced by the presence of NP[OC6H4(C02Na)-4]2)n- The same holds for the morphology of the hydoxy-apatite formed. 

In bone, a CaBP called osteocalcin contains 49 amino acids (M.W. 5500-6000). Its synthesis is stimulated by 1,25-(0H)2D. Osteocalcin contains four residues of y-carboxyglutamic acid, which require vitamin K for their synthesis and are important as binding sites for calcium (Chapter 36). Although vitamin K deficiency reduces the osteocalcin content of bone, it does not cause functional bone defects. For this reason, osteocalcin may function in calcium mobilization rather than deposition. Alternatively, as an effective inhibitor of hydroxyapatite formation, it may prevent overmineralization of bone. 1,25-(OH)2D increases y-glutamyl carboxylase activity in the renal cortex. The relationship between vitamin D and vitamin K needs clarification. 

Li L, Buchet R, Wu Y (2008) Dimethyl sulfoxide-induced hydroxyapatite formation a biological model of matrix vesicle nucleation to screen inhibitors of mineralization. Anal Biochem 381 123-128... 

Table 3.2. Biological inhibitors of hydroxyapatite formation from aqueous solution...

Fulmer M.T. and Brown P.W. 1993. Effects of Na2HP04 and NaH2P04 on hydroxyapatite formation. J. Biomed. Mater. Res. 27 1095-1102. 

S.H. Rhee, J. Tanaka, Hydroxyapatite formation on cellulose cloth induced by citric acid, J. Mater. Sci. Mater. Med. 11 (2000) 449-452. 

Hydroxyapatite Formation Study. The interaction of synthetic hydroxyapatite with treated polyethylene films was evaluated using a modification of a procedure published by Golomb and Wagner (5). Polyethylene films were phosphonylated and converted to potassium and calcium phosphonates. 

Hydroxyapatite Formation Study. The directed growth of hydroxyapatite crystals on the modified polyethylene surfaces was attempted in vitro in order to assess, indirectly, the propensity of the materials for integration with natural HA in vivo. Untreated PE films as well as PE films bearing phosphonyl dichloride and potassium phosphonate moieties were incubated in the calcium and phosphate salt solution, used... 

Fluoride ions have an important effect on the formation of the inorganic phase in enamel since they act as a catalyst for the conversion of octacalcium phosphate to hydroxyapatite. This has been demonstrated for extremely low levels of fluoride in vitro and it has also been shown that the presence of fluoride during hydroxyapatite formation improves the perfection of the crystals. 

---