Apatite, biological

The so-called bioactive ceramics have been attractive because they spontaneously bond to living bone, however, they are much more brittle and much less flexible than natural bone. Previous studies reported that the essential condition for ceramics to show bioactivity is formation of a biologically active carbonate-containing apatite on their surfaces after exposure to the body fluid [337]. Calciiun sulfate was also used [338]. 

Phosphate also plays a central role in the transmission and control of chemical energy within the cells primarily via the hydrolysis of the terminal phosphate ester bond of the adenosine triphosphate (ATP) molecule (Fig. 14-3b). In addition, phosphate is a necessary constituent of phospholipids, which are important components in cell membranes, and as mentioned before, of apatite, which forms structural body parts such as teeth and bones. It is not surprising, therefore, that the cycling of P is closely linked with biological processes. This connection is, in fact, inseparable as organisms cannot exist without P, and their existence controls, to a large extent, the natural distribution of P. 

Lee-Thorp, J.A. and Van der Merwe, N.J. 1991 Aspects of the chemistry of modern and fossil biological apatites. Journal Archaeological Science 18 343-354. 

The minerals in skeletal mammalian tissues are biological apatites (the plural is used here deliberately because they exist as a continuum of structures... 

The main assumption in this model is that matrix carbonate in solution is the principle agent for alteration of carbonates in biological apatites. Although the liquid and solid carbonate phases differ isotopically (the latter is enriched by about 8%o relative to former, under equilibrium conditions), the isotopic relationship between phases is well-defined (Emrich et al. 1970) hence values obtained from solid are at least representative of the dissolved phase. As shown in the model in Fig. 5.3, isotopic contamination of... 

Krueger, HW. 1991 Exchange of carbon with biological apatite. Journal of Archaeological Science 18 355-361. 

LeGeros, R.Z. 1981 Apatites in biological systems. In Pamplin, B., ed.. Progress in Crystal Growth and Characterization. Vol. 4. New York, Pergamon Press W5. 

Despite its relatively late discovery, phosphorus is the eleventh most abundant element in Earth s crustal rock. It has been estimated that world reserves of phosphate rock are sufficient to last for several hundred years. Virtually all phosphorus deposits contain apatite, whose general formula is Caj (P04)3 X, where X — OH, or Cl. Fluoroapatite is the least soluble, hence most abundant, of the three apatite minerals. Phosphorus Is found in aqueous systems as HPOq and H2 PO4 ions. In biological organisms, phosphorus is a component of nucleic acids and energy-shuttling molecules such as ATP. 

Nakano, T., Kaibara, K., Tabata, Y., Nagata, N., Enomoto, S., Marukawa, E. and Umakoshi, Y. (2002) Unique alignment and texture of biological apatite crystallites in typical calcified tissues analyzed by microbeam X-ray diffractometer system. Bone, 31, 479-487. 

Abe, Y., Kokubo, T. and Yamamuro, T. (1990) Apatite coating on ceramics, metals and polymers utilizing a biological process. Journal of Materials Science-Materials in Medicine, 1, 233-238. 

The collagen fibers leave small compartments where apatite nanocrystals are deposited during a controlled biomineralization process [20]. The collagen acts as a structural framework in which plate-like nanocrystals of carbonated hydroxyapatite (CHA) are embedded to strengthen the bone. The chemical formula of biological CHA can be represented as follows ... 

Poly(oxyethylene)-Si02 ormosils have been prepared as an approach to the preparation of biologically active polymer-apatite composites. For this purpose, Yamamoto et al. [72] obtained these Class II hybrids from triethoxysilyl-terminated poly(oxyethylene) (PEG) and TEOS by using the in situ sol-gel process. After being subjected to the biomimetic process to form the bone-like apatite layer, it was found that a dense apatite layer could be prepared on the hybrid materials, indicating that the silanol groups provide effective sites for CHA nucleation and growth. 

McConnell, D. (1973). Apatite. Its Crystal Chemistry, Mineralogy, Utilization, and Geologic and Biologic Occurences. Springer-Verlag, Vienna. 

Interest in the nature of interactions between shortchain organic surfactants and large molecular weight macromolecules and ions with hydroxyapatite extends to several fields. In the area of carles prevention and control, surfactant adsorption plays an important role in the Initial states of plaque formation (1-5) and in the adhesion of tooth restorative materials ( ). Interaction of hydroxyapatite with polypeptides in human urine is important in human biology as hydroxyapatite has been found as a major or minor component in a majority of kidney stones ( 7). Hydroxyapatite is used in column chromatography as a material for separating proteins (8-9). The flotation separation of apatite from... 

Geochim Cosmochim Acta 60 4811 829 Kohn MJ (1999) Why most dry rocks should cool wet . Am Miner 84 570-580 Kohn MJ, Ceding TE (2002) Stable isotope compositions of biological apatite. Rev Miner Geochem 48 455 88... 

There are multiple applications of fluoridated bioceramics, essentially as bone and tooth substitutes (Table 1), involving bulk ceramics, glasses, composite materials and coatings for medical devices and surface treatments. In some cases, fluoride ions can leach out of the material inducing a direct biological effect in a soluble form. However, considering the affinity of fluoride ions for apatite... 

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