Calcium phosphate pastes

Bohner M, Baroud G. Injectability of calcium phosphate pastes. Biomaterials. 2005 May 26(13) 1553-63. 

Habib M, Baroud G, Gitzhofer F, Bohner M. Mechanisms underlying the bmited injectabibty of hydraulic calcium phosphate paste. Acta Biomaterialia. 2008 4(5) 1465-71. 

Bohner M, Doebelin N, Baroud G. Theoretical and experimental approach to test the cohesion of calcium phosphate pastes. Eur Cell Mater. 2006 12 26-35. 

The measurement of pH in cheese making is extremely important to control fermentation/acid production and hence the final quality. While there are no standard methods available for measuring cheese pH, there have been few methods reported in the literature. One method involves preparing a slurry of 10 g of grated cheese in water and measuring the pH potentiometrically (Fox et al., 2004a). However, this method may alter the balance between colloidal and soluble calcium phosphate and hence it is preferable to measure the pH of the cheese directly. The quinhydrone electrode method (Marshall, 1992) measures the pH directly. The potential (mV) created by a paste of cheese and quinhydrone in saturated KC1 is measured and used to determine the pH at a particular temperature. 

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. 

The biocompatible CBPC development has occurred only in the last few years, and the recent trend has been to evaluate them as biocompatible ceramics. After all, biological systems form bone and dentine at room temperature, and it is natural to expect that biocompatible ceramics should also be formed at ambient temperature, preferably in a biological environment when placed in a body as a paste. CBPCs allow such placement. We have discussed such calcium phosphate-based cements in Chapter 13. Calcium-based CBPCs, especially those constituting hydroxyapatite (HAP), are a natural choice. HAP is a primary mineral in bone [3], and hence calcium phosphate cements can mimic natural bone. Some of these ceramics with tailored composition and microstructure are already in use, yet there is ample room for improvement. This Chapter focuses on the most recent biocompatible CBPCs and their testing in a biological environment. To understand biocompatible material and its biological environment, it is first necessary to understand the structure of bone and how it is formed. 

Murray RW, Leinen M, Isem AR (1993) Biogenic flux of A1 in the central equatorial Pacific Ocean Evidence for increased productivity during glacial periods. Paleoceanogr 8 651-670 Murray RW, Knowlton C, Leinen M, Mix AC, Polski CH (2000) Export production and carbonate dissolution in the central equatorial Pacific Ocean over the past 1 Ma. Paleoceanogr 15 570-592 Nancollas GH, Amjad Z, Koutsoukas P (1979) Calcium phosphates-speciation, solubility, and kinetic considerations. Am Chem Soc Symp Ser 93 475-497... 

Bone China has a similar recipe to hard-paste porcelain, but with the addition of 50% animal bone ash (calcium phosphate). This formulation improves strength, translucency, and whiteness of the product and was perfected by Josiah Spode at the end of the eighteenth century. It was then known as English China or Spode China. ... 

Table 2.3 List of some non-setting non-allogenic pastes with indication of producer, product name, composition and form (pre-mixed or to be mixed). Denominations HA = Hydroxyapatite / -TCP = / -Tricalcium phosphate BCP = diphasic calcium phosphate (composite between HA and /3-TCP) CMC = carboxymethylcellulose H PMC hydroxypropylmethylcellulose... 

Kurashina K, Kurita H, Hirano M, Kotani A, Klein CP, de Qroot K. In vivo study of calcium phosphate cements implantation of an alpha-tricalcium phosphate/ dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement paste. Biomaterials. 1997 Apr 18(7) 539-43. 

Calcium phosphate cements, as an example of in situ setting ceramics, are made from a powder containing anhydrous calcium phosphate and an aqueous phosphate solution. Once mixed, calcium phosphate precipitates in an entanglement of crystals that form a paste [91]. 

Bone canents are closely related to bone substitutes and are mostly derived from similar calcium phosphate materials. One cement is made from a paste of Ca3(P04)2 or Ca3(P04)2 + Ca(H2P04>2 + CaC03, in Na2HP04 solution, while another consists of a 1 1 mixture of Ca3(P04>2 and anhydrous CaHP04. Various setting rates, down to about 5 min, can be obtained. These cements are slowly converted to hydroxyapatite when placed in bone cavities moreover, they appear to encourage further bone growth [49-51]. 

In the past few decades, many methods such as physical machining and controlled oxidation have been used to improve the in vivo osseointegration of titanium-based implants. Calcium phosphate—based thin films such as HA have been used frequently on orthopaedic implants. As a new concept in tissue engineering, it has been suggested that HA has distinct luminescence properties allowing rapid identification of phase distribution of biomimetic apatite thin films. In a research smdy, Sepahvandi et al. reported that the photoluminescence property can be used in the characterization and early detection of biomimetic bonelike apatite formation on the surface of alkaline-treated titanium implants (in SBF solution). 

Phosphorus recovery from wastewater accords with the demands of sustainable development of phosphate industry and the stringent environment quality standard. In this context, the past decade has seen a number of engineering solutions aiming to address phosphorus recovery from wastewater by precipitation of calcium phosphates in a recyclable form (Morse et al., 1998). An advanced alternative is to apply the so called pellet reactor (Seckler, 1994). 

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