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Biomolecules and Tissue Properties
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
There are other types of calcium phosphate in bone, not just HAP, although it is the main type. Other types of calcium phosphate present include amorphous calcium phosphate, tricalcium phosphate, brushite, and octacalcium phosphate. There are different theories about the formation of mineral, specifically HAP in bone. It is theorized that amorphous calcium phosphate is composed of mainly tricalcium phosphate. The Ca2+ and PO4− ions begin to aggregate in a simple manner and then over time form a more complex, crystalline structure11,12 (Figure 3.22). As time passes, the amorphous material would be converted into a crystalline mineral. This process would be hindered by the presence of inhibitors such as adenosine triphosphate (ATP), pyrophosphate, diphosphate, and some phospholipids. Another theory suggests that other types of calcium phosphate are produced as precursors, which are then hydrolyzed into HAP. It has been proposed that other calcium phosphates (such as octacalcium phosphate or brushite) are initially produced and then converted into HAP (Figure 3.22). Tricalcium phosphate, Ca3(PO4)2, (also known as calcium orthophosphate, tertiary calcium phosphate, and tribasic calcium phosphate) is one of the main combustion products of bone (bone ash). Another common form of calcium phosphate is brushite (also known as Dicalcium Phosphate Dihydrate [DCPD]). It is a hydrated calcium phosphate with the composition CaHPO4·2H2O. It is usually the calcium phosphate source of kidney stones.
Nutrient removal from wastewaters using treated incineration residues of expired medications: Kinetics, thermodynamics and isotherm modeling
Published in Particulate Science and Technology, 2018
K. Khelif, Z. Salem, L. Boumehdi
According to Li et al. (2013), the higher occurrence of Ca2+ ions provided more active sites for P immobilization. Takaya et al. (2016) suggested that PO4-P sorption mechanisms are thought to be dependent on metal ion reactions (precipitation, surface deposition), surface area and surface functionality. He also found some positive correlation between PO4-P adsorption and Ca or Mg contents. Lu et al. (2009) showed that the major precipitate during the removal of phosphate by fly ash was brushite (CaHPO4 · 2H2O). The crystals of brushite (CaHPO4 · 2H2O) are formed on particles surfaces of seeds according to the following reaction:
Sr/Na co-doped brushite coating on SiC–C/C with brushite seeds
Published in Surface Engineering, 2019
Leilei Zhang, Yao Guo, Hejun Li, Fei Zhao, Lina Pei, Kejie Guan, Feiyan Zhu
Calcium phosphate (CaP) coated carbon/carbon composites (CC) are attractive biomaterials in bone tissue reconstruction because they could combine excellent biocompatibility of CaP and suitable mechanical properties of CC. For CaP coating materials, brushite (CaHPO4·2H2O), octacalcium phosphate (Ca8H2(PO4)6·5H2O), tricalcium phosphate (Ca3(PO4)2) and hydroxyapatite (Ca10(PO4)6(OH)2) are prominent CaP component found in human bone [1]. Among these CaP materials, brushite is biocompatible with bone cells and has been frequently applied as the initial component of bone cements for clinical application [2]. Further, CaP could be doped with single or double ions to replace Ca2+, PO43− or OH− in its structure. The doped ions may alter the crystal structure, phase stability, solubility and bioactivity of CaP [3]. Several double-doped ions have been investigated, such as silicate/silver [4], iron/zinc [5], strontium/zinc [6], strontium/sodium [7], etc. Particular attention is focused on strontium/sodium co-doped ions. Strontium is capable of preventing bone resorption and suppressing the bone lose, whereas sodium could improve the cell adhesion and bone metabolism [8,9]. Thus, strontium/sodium co-doped brushite (SSCB) may be potential coating materials. For CC, CC process suitable elastic modulus that matches with the human bone [10]. Further, CC could be surface modified with SiC layer, forming SiC-modified CC (SC). SC could keep the mechanical properties of CC and promote the compatibility between CC and CaP coating due to the buffer and transition effects of the SiC layer.