Solubility of Hydroxyapatite and Related Thermodynamic Data

Mahapatra, P. P.; Mishra, H.K.; Chickerur, N. S.

doi:10.1016/0040-6031(82)85212-x

Cited by 13 publications

(7 citation statements)

References 6 publications

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“…Evidently, the nucleation of DCPD is easier than that of HAp at lower pH values, even though HAp is in fact less soluble than DCPD. Thus, the relatively large excess of OCP added resulted in the formation of metastable DCPD, consistent with the report by Mahapatra et al [1982] that DCPD was formed in the presence of excess HAp solid in 0.165 M NaNO 3 solution below pH ϳ 7.2 -that is, sufficient supersaturation results in an Ostwald succession, where the next most stable solid is formed first, rather than what the ultimate thermodynamic equilibrium requires. This is conditional on the absence of nucleation by the final phase.…”

Section: Discussionsupporting

confidence: 76%

Solid Titration of Octacalcium Phosphate

Pan

Darvell

2009

Caries Res

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Octacalcium phosphate (OCP) is of considerable importance as a precursor in the formation of dental enamel and an intermediate phase in the precipitation of hydroxyapatite (HAp) in bone. However, agreement is poor on the solubility product (pK_sp), possibly due to the formation of the more stable phase HAp. The system was investigated using solid titration, which has shown reliability in work on HAp and related fluoride minerals, with OCP in 100 mM KCl at 37.0 ± 0.1°C. The constitution of the end point precipitate was determined by X-ray diffraction and selected-electron area diffraction; the particle morphology and elements present were examined by high-resolution field emission scanning, transmission electron microscopy and energy-dispersive X-ray analysis. The titration curve for OCP was found for pH ∼3.4–7.4. The precipitate was HAp at pH 3.6 and 4.5; no residual OCP or other phase was detected. Dicalcium phosphate dihydrate (DCPD) was then found to form at pH 3.6 on further addition of OCP titrant after equilibrium had been achieved, possibly due to easier nucleation at lower pH. However, markedly crystalline HAp was formed in equilibrium for OCP titration with HAp seeding, verifying HAp as the more stable phase. A solubility isotherm for OCP was not obtained as HAp appears to be less soluble in the pH range studied. This adds weight to the view that HAp may be the most stable phase of all calcium phosphates, with further doubt being cast on DCPD being the most stable phase below pH 4.2. However, metastable DCPD may form in an Ostwald succession, depending on supersaturation and nucleation conditions.

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Section: Discussionsupporting

confidence: 76%

Solid Titration of Octacalcium Phosphate

Pan

Darvell

2009

Caries Res

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“…3(b)]. Since precipitation of CAP is an endothermal process,32, 33 an increase in temperature will, according to Le Châtelier's principle, yield lower solubility and greater supersaturation. Consequently, boiling leads to completion of the solidification process and prevents the ripening effect and formation of layered structures, such as those displayed in Figure 3b.…”

Section: Resultsmentioning

confidence: 99%

Association of noninvasively measured renal protein biomarkers with histologic features of lupus nephritis

Brunner

Bennett

Mina

et al. 2012

Arthritis & Rheumatism

143

111

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Objective To investigate the relationship of urinary biomarkers (UBM) and established measures of renal function (EMRF) to the histological findings with lupus nephritis (LN); and to test whether certain combinations of the above mentioned laboratory measures are diagnostic of specific histological features of LN. Methods Urine samples of 76 patients were collected within 2 months of a kidney biopsy and assayed for the UBM: lipocalin-like prostaglandin-D synthetase (LPGDS), α1-acid-glycoprotein (AAG), transferrin (TF), ceruloplasmin (CP), neutrophil-gelatinase associated lipocalin (NGAL), and monocyte chemotactic factor 1 (MCP1). Using non-parametric analyses, UBM and EMRF levels were compared to histological features seen with LN: mesangial expansion, capillary proliferation, crescent formation, necrosis, wire loops, fibrosis, tubular atrophy, and epimembranous deposits. The area under the receiver operating characteristic (AUC) curve was calculated to predict LN activity, chronicity or membranous LN. Results There was a differential increase of the UBM that formed a pattern reflective of specific histological features seen with active LN. The combination of MCP1, AAG, CP plus protein:creatinine ratio were excellent in predicting LN activity (AUC=0.85). NGAL together with creatinine clearance plus MCP1 was an excellent (AUC=0.83) and MCP1, AAG, creatinine clearance plus C4 (AUC=0.75) a good diagnostic test of LN chronicity and membranous LN, respectively. Conclusions Select UBM are associated with specific tissue changes observed with LN activity and chronicity. Especially in combination with select EMRF, UBM are well-suited to non-invasively quantify LN activity, LN chronicity, and the presence of membranous LN.

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“…3(b)]. Since precipitation of CAP is an endothermal process, 32,33 an increase in temperature will, according to Le Châ telier's principle, yield lower solubility and greater supersaturation. Consequently, boiling leads to completion of the solidification process and prevents the ripening effect and formation of layered structures, such as those displayed in Figure 3b.…”

Section: Resultsmentioning

confidence: 99%

Phase composition control of calcium phosphate nanoparticles for tunable drug delivery kinetics and treatment of osteomyelitis. I. Preparation and drug release

Uskoković

Desai

2012

J Biomedical Materials Res

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Developed in this study is a multifunctional material for simultaneous osseoinduction and drug delivery, potentially applicable in the treatment of osteomyelitis. It is composed of agglomerates of nanoparticles of calcium phosphate (CAP) with different monophasic contents. The drug loading capacity and the release kinetics were investigated on two model drug compounds with different chemical structures, sizes and adsorption propensities: bovine serum albumin and fluorescein. Loading of CAP powders with small molecule drugs was achieved by physisorption and desiccation-induced agglomeration of nanoparticulate subunits into microscopic blocks. The material dissolution rate and the drug release rate depended on the nature of the CAP phase, decreasing from monocalcium phosphate to monetite to amorphous CAP and calcium pyrophosphate to hydroxyapatite. The sustained release of the two model drugs was shown to be directly relatable to the degradation rate of CAP carriers. It was demonstrated that the degradation rate of the carrier and the drug release kinetics could be made tunable within the time scale of 1–2 h for the most soluble CAP phase, monocalcium phosphate, to 1–2 years for the least soluble one, hydroxyapatite. From the standpoint of antibiotic therapy for osteomyelitis, typically lasting for six weeks, the most prospective CAP powder was amorphous CAP with its release time scale for a small organic molecule, the same category to which antibiotics belong, of 1 – 2 months under the conditions applied in our experiments. By combining these different CAP phases in various proportions, drug release profiles could be tailored to the therapeutic occasion.

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Solubility of Hydroxyapatite and Related Thermodynamic Data

Cited by 13 publications

References 6 publications

Solid Titration of Octacalcium Phosphate

Solid Titration of Octacalcium Phosphate

Association of noninvasively measured renal protein biomarkers with histologic features of lupus nephritis

Phase composition control of calcium phosphate nanoparticles for tunable drug delivery kinetics and treatment of osteomyelitis. I. Preparation and drug release

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