Precipitation calcium phosphate

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... 

Temperature of the system When inhibitors are used in the 0-100°C range it is usually found that higher concentrations become necessary at the higher temperatures Other inhibitors can lose their effectiveness altogether as the temperature is raised. A prime example of this is the polyphosphate type of inhibitor. This is effective in circulating systems at temperatures below about 40°C, but at higher temperatures reversion to orthophosphate can occur and this species is ineffective at the concentrations at which it will then be present. If calcium ions are present, additional loss of inhibitor will occur due to calcium phosphate precipitation. 

Sodium carboxymethyl chitin and phosphoryl chitin had most evident influences on the crystallization of calcium phosphate from supersaturated solutions. They potently inhibited the growth of hydroxyapatite and retarded the rate of spontaneous calcium phosphate precipitation. These chitin derivatives were incorporated into the precipitate and influenced both the phase and morphology of the calcium phosphate formed (flaky precipitate resembling octacalcium phosphate instead of spherical clusters in the absence of polysaccharide) [175]. 

C18-0127. Phosphate ions are a major pollutant of water supplies. They can be removed by precipitation using solutions of Ca ions because the of calcium phosphate is 2.0 X 10 . Suppose that 3.00 X 10 L of wastewater containing P 03 at 2.2 X 10 M is treated by adding 120 moles of solid CaCl2 (which dissolves completely), (a) What is the concentration of phosphate ions after treatment (b) What mass of calcium phosphate precipitates ... 

Classical gene transfer methods still in use today are diethylamino ethyl (DEAE)-dextran and calcium phosphate precipitation, electroporation, and microinjection. Introduced in 1965, DEAE-dextran transfection is one of the oldest gene transfer techniques [2]. It is based on the interaction of positive charges on the DEAE-dextran molecule with the negatively charged backbone of nucleic acids. The DNA-DEAE-dextran complexes appear to adsorb onto cell surfaces and be taken up by endocytosis. 

Patients with tumor lysis syndrome experience a wide range of metabolic abnormalities. The massive cell lysis that occurs leads to the release of intracellular electrolytes, resulting in hyperkalemia and hyperphosphatemia. High concentrations of phosphate bind to calcium, leading to hypocalcemia and calcium phosphate precipitation in the renal tubule. Purine nucleic acids are also released that are subsequently metabolized to uric acid... 

Electrolyte disturbances that develop in patients with tumor lysis syndrome should be managed aggressively to avoid renal failure from hyperphosphatemia and hypocalcemia and cardiac signs from hyperkalemia. One exception pertains to the use of intravenous calcium for hypocalcemia. Adding calcium may cause further calcium phosphate precipitation in the presence of hyperphosphatemia and should be used cautiously. 

The Food and Drug Administration (FDA) published a safety alert in 1994 in response to two deaths associated with calcium-phosphate precipitation in PN.16 Autopsy reports from these patients revealed diffuse micro vascular pulmonary emboli containing calcium-phosphate precipitates. Because calcium and phosphate can bind and precipitate in solution, caution must be exercised when mixing these two electrolytes in PN admixtures. Several factors can affect calcium-phosphate solubility, including... 

Amino acid concentration. Primary factor that affects pH of the PN admixture the higher the concentration of amino acids, the higher is the amount of calcium and phosphate that can remain in solution (phosphate likely binds with amino acids and less is available to bind with calcium), therefore lowering the risk of calcium-phosphate precipitation. 

Time. More calcium and phosphate will dissociate over time, increasing the risk for calcium-phosphate precipitation. 

Temperature. As temperature increases, more calcium and phosphate dissociate and increase the risk of calcium-phosphate precipitation. 

Calcium phosphate precipitation may also be involved in the fixation of phosphate fertilizer in soils. Studies of the uptake of phosphate on calcium carbonate surfaces at low phosphate concentrations typical of those in soils, reveal that the threshold concentration for the precipitation of the calcium phosphate phases from solution is considerably increased in the pH range 8.5 -9.0 (3). It was concluded that the presence of carbonate ion from the calcite inhibits the nucleation of calcium phosphate phases under these conditions. A recent study of the seeded crystal growth of calcite from metastable supersaturated solutions of calcium carbonate, has shown that the presence of orthophosphate ion at a concentration as low as 10-6 mol L" and a pH of 8.5 has a remarkable inhibiting influence on the rate of crystallization (4). A seeded growth study of the influence of carbonate on hydroxyapatite crystallization has also shown an appreciable inhibiting influence of carbonate ion.(5). 

A different application of visible microscopy was pioneered by Gomori. In 1941 he showed that alkaline phosphatase could be specifically located by its hydrolysis of soluble phosphate esters (initially glycerophosphate). If calcium ions were present in the medium in which the sections were incubated, insoluble calcium phosphate precipitated as a result of the action of the hydrolase. The site of the precipitate could be visualized if cobalt or lead salts were subsequently added to replace calcium and the sections exposed to hydrogen sulfide. In principle many hydrolases and other enzymes could be studied using the appropriate substrates and precipitants. It was important to ensure that the products of the enzyme reactions did not diffuse from the sites where the enzymes were located. It was also essential that the reagents could reach the enzyme site. 

Synonyms calcium orthophosphate calcium phosphate tricalcium phosphate tertiary calcium phosphate precipitated calcium phosphate bone ash (technical product). 

Table 11.2. Vector systems used to deliver genes into mammalian cells. To date, the majority of clinical trials undertaken have utilized retroviral vector systems. Non-viral systems have generally been employed least often, although some, e.g. nucleic acid-containing liposomes, may be used more extensively in the future. Some of the methods tested, e.g. calcium phosphate precipitation, electroporation and particle acceleration, are unlikely to be employed to any great extent in gene therapy protocols...

Besides local toxicity, discussed above, there are numerous other modes of potential adverse interactions involving excipients (19,20). Many of these pose little threat provided the amounts of excipients are constrained to certain levels. Excessive amounts, however, can cause problems, particularly for patients who are intolerant of even modest levels. Commonly used phosphate buffers may cause calcium loss with formation of insoluble calcium phosphates when such buffers are administered in over-ambitious amounts (21). Calcium phosphate precipitation has been noted particularly in nutritional parenteral admixtures for neonates because of the high nutrient requirements. Similarly, renal toxicity has been associated with depletion of zinc and other trace metals caused by large parenteral doses of ethylenediaminete-traacetic acid (EDTA) (22). Excessive absorption of glycine solutions, when used as irrigants during transurethral resections, can cause hyponatremia, hypertension, and confusion (23). The use of preservatives has been associated with cardiac effects in a few patients (24). Premature neonates were found to be at risk for receiving toxic amounts of benzoic acid or benzyl alcohol in bacteriostatic solutions used to flush intravenous catheters (25). 

Freezing milk causes crystallization of pure water and the unfrozen liquid becomes more saturated with respect to various salts. Some soluble calcium phosphate precipitates as Ca,(POj2, with the release of H+ and a decrease in pH (e.g. to 5.8 at — 20°C). 

Fleisch, H., Neuman, F. Quantitative aspects of nucleation in calcium phosphate precipitation. J. Amer. Chem. Soc. 82, 996 (1960)... 

The insoluble Ca(II) salts of weak acids, such as calcium phosphate, carbonate, and oxalate, serve as the hard structural material in bone, dentine, enamel, shells, etc. About 99% of the calcium found in the human body appears in mineral form in the bones and teeth. Calcium accounts for approximately 2% of body weight (18,19). The mineral in bones and teeth is mosdy hydroxyapatite [1306-06-5] having unit cell composition Ca10(PO4)6(OH)2. The mineralization process in bone follows prior protein matrix formation. A calcium pumping mechanism raises the concentrations of Ca(II) and phosphate within bone cells to the level of supersaturation. Granules of amorphous calcium phosphate precipitate and are released to the outside of the bone cell. There the amorphous calcium phosphate, which may make up as much as 30—40% of the mineral in adult bone, is recrystallized to crystallites of hydroxyapatite preferentially at bone collagen sites. These small crystallites do not exceed 10 nm in diameter (20). 

The majority of cooling systems around the world are small plants operating under alkaline conditions without acid dosing, and, unless periodic and specific tests are performed by the water treater to evaluate the potential for calcium phosphate precipitation in these systems, deposition can and probably will occur. 

Tumor tissue has also been demonstrated to take up naked pDNA following direct intratumoral injection, but this ability may be dependent on tumor type and the pDNA construct. In an important study by Vile and Hart (1993), mice bearing subcutaneous (s.c.) B16F1 melanoma or Colo 26 colon carcinoma were injected intratumorally with naked P -gal pDNA or P -gal pDNA/calcium phosphate precipitates. The tumors were collected on days 2, 4, 6 and 10 after the pDNA intratumoral injection. A gradual increase in blue-staining cells was found in the transfected melanomas with 10-15% of the cells expressing /3-gal by day ten. In contrast, none of the colon carcinoma tumors was positive for /3-gal. One explanation for the lack of in vivo transfection of the colon carcinoma is that the /3-gal pDNA constmcts contained melanoma-specific promoters (tyrosinase and TRP promoters). This study demonstrated that using an appropriate promoter established tumors could take up and express naked pDNA. 

This method is extremely sensitive to pH changes which can lead to inconsistent transfection efficiencies, especially when using homebrew transfection buffers. To some extent, this sensitivity can be limited by the use of commercially available kits containing chemicals and buffers that have undergone quality control procedures, ensuring better reproducibility of results and less lot-to-lot variation. Although the costs per transfection for this method are unrivaled, the attractiveness of calcium phosphate precipitation has declined over the past 15 years, partly due to the trickiness of the method itself, the limited transfection efficiencies, and the narrow cell spectrum for which it is suitable, and partly because more modem and efficient DNA delivery methods have emerged. 

Phelan and Mattigod (1987) studied calcium phosphate precipitation from stable supersaturated solutions using pH/Ca-stat and pH-stat. The pH and Ca2+ activity of the titrand were kept constant utilizing ion-specific electrodes attached to automatic titrators. A schematic diagram of the apparatus used by Phelan and Mattigod is shown in Fig. 3.2. 

Campbell 1977). The resulting phosphate ions may be removed as a calcium phosphate precipitate by adding lime. Campbell (1977) claimed this process reduced the phosphorus levels in phossy water below the limit of detection (<22 pg/L). 

One approach developed by Isis Innovation Limited (a wholly-owned subsidiary of the University of Oxford) involves the precipitation of calcium phosphate onto collagen at room temperature. When o-phosphoserine is added to the reaction, the calcium phosphate precipitates onto the collagen in the form of small "needles." These structures provide abundant surface area on which osteoblasts and other hone cells can become established. 

Greenberg, G., Hasson, D. and Semiat, R. (2005) Limits of RO recovery imposed by calcium phosphate precipitation. Desalination, 183, 273-288. 

Jordan M, Schallhorn A, Wurm FM (1996), Transfecting mammalian cells optimization of critical parameters affecting calcium phosphate precipitate formation, Nucleic Acids Res. 24 596-601. 

To grow sufficient crops, you will need large amounts of calcium phosphate fertilizer. You can make this compound by combining the phosphate solution in the stream with calcium cations. Simulate this reaction in the laboratory. Design a procedure to find the mass of dry calcium phosphate precipitate. Mix 50 mL of a 0.10 mol/L aqueous solution of sodium phosphate with sufficient calcium nitrate to obtain a precipitate. Filter the precipitate, dry it, and determine its mass. 

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