Effect of calcium ions on transformation brushite to hydroxyapatite in aqueous solutions

Štulajterová, Radoslava; Medvecký, Ľubomír

doi:10.1016/j.colsurfa.2007.08.036

Cited by 83 publications

(35 citation statements)

References 15 publications

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“…[13][14][15][16][17][18][19][20] The application of HA coatings depends on its crystallite size. The obtained brushite coatings (CaHPO 4 ·2H 2 O), were converted to hydroxyapatite (HA) by soaking in simulated body fluid (SBF) for 2, 7 and 14 days.…”

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confidence: 99%

The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid

Djošić

Mitrić²,

Mišković‐Stanković³

2015

JSCS

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Calcium phosphate coatings were electrochemically deposited on titanium from an aqueous solution of Ca(NO 3 ) 2 and NH 4 H 2 PO 4 at a current density of 10 mA cm -2 for a deposition time of 15 min. The obtained brushite coatings (CaHPO 4 ·2H 2 O), were converted to hydroxyapatite (HA) by soaking in simulated body fluid (SBF) for 2, 7 and 14 days. The brushite and hydroxyapatite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was shown that increasing the soaking time increased the porosity, roughness and crystallite domain size of the HA coatings and decreased the unit cell parameters and unit cell volume, while the mean pore area of HA was unaffected. The calcium and phosphorus ions concentrations in SBF were determined by atomic absorption spectroscopy (AAS) and UV-Vis spectroscopy, respectively, and a mechanism of HA growth based on dissolution-precipitation was proposed.Available on line at www.shd.org.rs/JSCS/ DJOŠIĆ, MITRIĆ and MIŠKOVIĆ-STANKOVIĆThe main constituents of human bone are calcium orthophosphates, collagen and water. Hydroxyapatite (HA, Ca 10 (PO 4 ) 6 (OH) 2 ), constitutes the majority of the inorganic component. HA is the only compound among calcium phosphatebased ceramics that is stable in a physiological environment and is biologically active. Applications of HA bioceramics are based on its excellent bioactivity, biocompatibility and porous structure. Both the micro-and macro-porosity of HA coatings are important. The macroporosity controls access of tissue and biological fluids to HA coatings. The microporosity controls protein adsorption, body fluid circulation and the resorption rate of calcium phosphate. The porous structure of HA improves the mechanical interlock between the cells and the surface of an implant, promotes osteoconductivity and enhances the adhesion between natural bone and an implant by the formation of an apatite layer. 3-5 Besides the coating porosity, a very important characteristic is the roughness of a coating, because the biocompatibility and corrosion resistance of implants are, also, determined by surface microstructural properties, such as surface roughness and grain size, which influence cell attachment, proliferation and differentiation. 6,7 There are a great number of methods for HA preparation, 8-12 including transformation of more soluble metastable phosphates, as precursors, e.g., brushite, monetite and octacalcium phosphate, in an aqueous environment. [13][14][15][16][17][18][19][20] The application of HA coatings depends on its crystallite size. It is possible to improve the characteristics of HA by controlling the particle size, particle distribution and agglomeration of precursors. Nanocrystalline HA exhibits a greater surface area and has better bioactivity than coarser crystals. [21][22][23][24] Brushite, CaHPO 4 ·2H 2 O, is a metastable compound, known as mineral brushite. It can be observed when calcium phosphate is precipitated at low pH values and low temperatures. 2...

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confidence: 99%

The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid

Djošić

Mitrić²,

Mišković‐Stanković³

2015

JSCS

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“…Indeed, DCPD grew for up to 3 days and then started to hydrolyze and to convert to HA and OCP. A complete transformation of DCPD to HA in a solution of Ca 2+ ions at basic pH has been also previously suggested by other authors [10]. Figure 1C shows the FTIR spectra collected for the particles grown at different times.…”

Section: Resultsmentioning

confidence: 56%

Formation of calcium phosphates by vapour diffusion in highly concentrated ionic micro‐droplets

Iafisco

Delgado-López

Gómez‐Morales

et al. 2011

Cryst. Res. Technol.

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In this work we have used the sitting drop vapour diffusion technique, employing the "crystallization mushroom" to analyze the evolution of calcium phosphate crystallization in micro-droplets containing high initial concentrations of Ca 2+ and HPO 4 2-. The decomposition of NH 4 HCO 3 solution produces vapours of NH 3 and CO 2 which diffuse through the droplets containing an aqueous solution of Ca(CH 3 COO) 2 and (NH 4 ) 2 HPO 4 . The result is the increase of pH by means of the diffusion of NH 3 gas and the doping of the calcium phosphate with CO 3 2-ions by means of the diffusion of CO 2 gas. The pH of the crystallization process is monitored and the precipitates at different times are characterized by XRD, FTIR, TGA, SEM and TEM techniques. The slow increase of pH and the high concentration of Ca 2+ and HPO 4 2-in the droplets induce the crystallization of three calcium phosphate phases: dicalcium phosphate dihydrate (DCPD, brushite), octacalcium phosphate (OCP) and carbonate-hydroxyapatite (HA). The amount of HA nanocrystals with needle-like morphology and dimensions of about 100 nm, closely resembling the inorganic phase of bones, gradually increases, with the precipitation time up to 7 days, whereas the amount of DCPD, growing along the b axis, increases up to 3 days. Then, DCDP crystals start to hydrolyze yielding OCP nanoribbons and HA nanocrystals.

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“…Even though scale are possibly mineralized with a mixture in compounds (growing edge vs mature mineral), large differences in ratio during scale regeneration were consistently found with different techniques and do support a switch in main mineral compound. The short time between the two different ratios, 24 h, suggest that this change in phase occurs very fast and is likely a thermodynamical process that does not require any involvement of proteins (Stulajterová and Medvecký, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…Both brushite (CaHPO 4 ·2H 2 O) and amorphous calcium phosphate have been suggested as precursors for hydroxyapatite formation (Christoffersen et al., 1989; Johnsson and Nancollas, 1992). Transformation of brushite to hydroxyapatite is a thermodynamically driven process that can occur under alkaline conditions even in a protein free environment (Stulajterová and Medvecký, 2008). Recently, new light has been shed on the nature of one mineral precursor phase in vivo: amorphous calcium phosphate was detected next to carbonated hydroxyapatite in mineralization of newly formed zebrafish fin rays (Mahamid et al., 2008).…”

Section: Introductionmentioning

confidence: 99%

Evidence for a hydroxyapatite precursor in regenerating cyprinid scales

Vrieze

Heijnen

Metz

et al. 2012

Journal of Applied Ichthyology

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Summary Collagen matrices, mineralized with calcium phosphates in a hydroxyapatite phase, are generally found in skeletal tissues. However, mechanisms of biomineral formation and regulation are still poorly understood. Elasmoid scales are part of the dermal skeleton and regenerate quickly when damaged or lost. This makes the scale a convenient target to study mineral compostion and formation. The X‐ray diffractogram of the mineral layer of carp scales only show speaks corresponding with hydroxyapatite. Energy‐dispersive X‐ray spectroscopy (EDX) during scanning electron microscopy identifies the elements calcium and phosphorus, which are restricted to the external layer of the scale. In contrast with various other species, calcium phosphate crystals are not present in the elasmodine layer. The clean boundary between calcified and uncalcified matrix suggests that subsequental mineralization of the elasmodine layer is inhibited. Quantification of the calcium and phosphorus content allows definition of a calcium/phosphorus ratio, which is indicative ofthe crystalline phase of the minerals. Through accurate measurements of total calcium and phosphorus (by ICP‐MS) in zebrafish scales, different ratios were found for newly formed (regenerating) scales compared to ontogenetic or completely regenerated scales. This shows that the mineral is not at first deposited as hydroxyapatite, but in a precursor phase. Although the nature of the phase remains to be established, this first analysis shows that cyprinids scales can easily be used to gain insights in the dynamics of biomineralization.

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Effect of calcium ions on transformation brushite to hydroxyapatite in aqueous solutions

Cited by 83 publications

References 15 publications

The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid

The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid

Formation of calcium phosphates by vapour diffusion in highly concentrated ionic micro‐droplets

Evidence for a hydroxyapatite precursor in regenerating cyprinid scales

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