Morphology Of Calcium Oxalate Crystals Research Articles

Elucidating the role of hyaluronic acid in the structure and morphology of calcium oxalate crystals

Recent surge in reports describing new additives that inhibiting the growth and nucleation of calcium oxalate (CaOx), the most common component of renal calculi or kidney stones, have rekindled interest in CaOx crystallization. In this in vitro study, the effect of hyaluronic acid (HA), a protein commonly found in urine, on the morphology and phase of the CaOx crystals is investigated. CaOx crystals were crystallized at pH 5.8 and 37 °C with a [Ca2+]:[C2O42-] ratio of 20:1, which is close to physiological conditions, in aqueous solution and artificial urine media. The obtained crystals were characterized structurally, morphologically and in terms of their surface charge. The crystals precipitated in aqueous solution without the HA additive were pure phase calcium oxalate monohydrate (COM) crystals with typical hexagonal morphology. The addition of HA partially promotes the transformation of COM into calcium oxalate dihydrate (COD) in aqueous solution. However, the only solid phase to form in artificial urine media with and without HA was identified as COD with tetragonal bipyramidal morphology. The results of this investigation will contribute to the understanding of the role HA plays on the morphology, structure, and thermal characteristics of CaOx and ultimately facilitate the development of effective treatments for kidney stones.

A facile preparation of rutin nanoparticles and its effects on controlled growth and morphology of calcium oxalate crystals

Switching of the growth-mode of calcium-containing crystals are of great research interest in materials science for the inhibition of pathological biomineralization. Rutin, a flavonol glycoside, was reported to have many pharmacological activities. However, the efficiency of rutin for practical therapeutic applications is still a challenge due to its low aqueous solubility and limited bioavailability. Herein, we report a facile method for preparation and characterization of rutin nanoparticles of ~200 nm in size and zeta potential of −22.70 ± 2.51 mV, based on anti-solvent co-precipitation using the synergistic effect of surfactants. Morphological and structural characterization of the nanoparticles was carried out with scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and powder X-ray diffraction (XRD) patterns. These results showed that rutin nanoparticles had a smaller particle size than raw rutin, and changed into an amorphous structure from the crystal structure of raw rutin. In vitro release profiles showed a sustained release rate of hydrophilic rutin nanoparticles corresponding to 83.5 ± 8.4% for a time period of 8 days. Furthermore, the influence of the rutin nanoparticles on the tuning of the growth and morphology of calcium oxalate (CaC2O4) crystals have been assessed using SEM, XRD patterns, TGA analysis and adsorption isotherms. The experimental results showed that the rutin nanoparticles could induce the formation of oval and octahedral calcium oxalate dihydrate (COD) crystals in a concentration-dependent manner. It is believed that the hydrogen bonding between the phenolic groups in rutin with carboxylate ions in crystals contributes to their increased adsorption and directing calcium oxalate monohydrate to dihydrate forms. These results indicated the potential application of rutin nanoparticles for in vivo lithiatic studies as well as for other pharmacological properties.

An in vitro evaluation of the effects of Urtica dioica and Fructus Urtica Piluliferae extracts on the crystallization of calcium oxalate

This study investigated crystallization of calcium oxalate in the presence of Urtica dioica and Fructus Urtica Piluliferae extracts. To evaluate the structures, morphologies and phase transformations of the crystals, X-ray diffraction, Raman and Fourier-transform infrared spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used. The results showed that both additives exerted significant effects on the crystallization process. When Fructus Urtica Piluliferae was used as an additive, the products were a mixture of the monohydrate and dihydrate forms of calcium oxalate. Both SEM and TEM confirmed that the crystals contain different morphologies including hexagonal prismatic and tetragonal bipyramidal forms. The addition of Urtica dioica to the crystallization medium led to the formation of the monohydrate form being efficiently inhibited with only the dihydrate crystals of calcium oxalate being formed over 30 days. A change in the morphology of the crystals from hexagonal prismatic to round nanocrystals was detected in the Urtica dioica medium. Moreover, zeta potential measurements showed that the surface of the crystals became more negative when compared with those prepared from the pure medium with the value increasing from –3.2 ± 0.5 to –40 ± 4.6 mV. This study demonstrated the modification of the structure and morphology of calcium oxalate crystals as well as the inhibition of its monohydrate form were possible using Urtica dioica and Fructus Urtica Piluliferae.

Effect of Blumea balsamifera extract on the phase and morphology of calcium oxalate crystals

ObjectiveCalcium oxalate crystals are found in majority of kidney stones with calcium oxalate monohydrate (COM) as one of the primary types of kidney stones. Various methods of treatment exist, including herbal treatment in the Philippines that uses the medicinal herb Blumea balsamifera (B. balsamifera). MethodsThe effect of B. balsamifera extract on the morphology of calcium oxalate crystals was studied by light microscopy, image analysis, powder X-ray diffraction and scanning electron microscopy. ResultsThe extract decreased the crystal size by 5.22%–82.62% depending on the degree of supersaturation. Through analysis of the projected area of the crystals, the extract was found to shift the phase of the crystals from COM to calcium oxalate dihydrate (COD). This shift in phase is significant with a COM to COD shift of 88.26% at 0.5 mg/mL of extract and 91.53% at 1.0 mg/mL of extract. Scanning election microscopic (SEM) images revealed aggregation of crystals at 0 mg/mL of extract. At 1.0 mg/mL of extract, the scanning electron micrographs showed discernible crystal unit boundaries. ConclusionB. balsamifera extract was observed to have decreased crystal size, shifted crystal phase from COM to COD and prevented the aggregation of calcium oxalate crystals.

Efficacy of Mixtures of Magnesium, Citrate and Phytate as Calcium Oxalate Crystallization Inhibitors in Urine

The main aim of the current study was to evaluate the effectiveness of mixtures of magnesium, citrate and phytate as calcium oxalate crystallization inhibitors. A turbidimetric assay in synthetic urine was performed to obtain induction times for calcium oxalate crystallization in the absence and presence of different mixtures of inhibitors. The morphology of calcium oxalate crystals in the absence or presence of inhibitors and mixtures of the inhibitors was evaluated in 2 crystallization experiments at low and high calcium oxalate supersaturation. The crystals formed were examined using scanning electron microscopy. Examination of crystallization induction times revealed clear inhibitory effects of magnesium, citrate and phytate on calcium oxalate crystallization, supporting usefulness in the treatment and prevention of calcium oxalate nephrolithiasis. Significant synergistic effects between magnesium and phytate were observed. Scanning electron microscopy images revealed that phytate is a powerful crystal growth inhibitor of calcium oxalate, totally preventing the formation of trihydrate and monohydrate. In addition to crystallization inhibition capacity, citrate and magnesium avoided calcium oxalate crystallization by decreasing its supersaturation. The synergistic effect between magnesium and phytate on calcium oxalate crystallization suggests that a combination of these 2 compounds may be highly useful as antilithiasis therapy.

Control of Phase and Morphology of Calcium Oxalate Crystals by Natural Polysaccharide, Gum Arabic

Controlled crystal growth of calcium oxalate was examined under the influence of Gum Arabic (GA) and urea at pH 4.0, 7.0, and 9.0. GA when alone directed the formation of calcium oxalate dihydrate (COD) up to 2.0% w/v concentration, whereas urea influenced the formation of calcium oxalate monohydrate (COM). The combination of urea and GA in mixed proportions (2.0% w/v each) led to the formation of nanocrystallites of COD. The present study on crystallization behavior of calcium oxalate under the influence of natural polysaccharides and urea may prove to be important in understanding the control of kidney stone formation.

Effect of poly(acrylic acid) molecular mass and end-group functionality on calcium oxalate crystal morphology and growth

A number of series of poly(acrylic acids) (PAA) of differing end-groups and molecular mass were used to study the inhibition of calcium oxalate crystallization. The effects of the end-group on crystal speciation and morphology were significant and dramatic, with hexyl-isobutyrate end groups giving preferential formation of calcium oxalate dihydrate (COD) rather than the more stable calcium oxalate monohydrate (COM), while both more hydrophobic end-groups and less-hydrophobic end groups led predominantly to formation of the least thermodynamically stable form of calcium oxalate, calcium oxalate trihydrate. Conversely, molecular mass had little impact on calcium oxalate speciation or crystal morphology. It is probable that the observed effects are related to the rate of desorption of the PAA moiety from the crystal (lite) surfaces and that the results point to a major role for end-group as well as molecular mass in controlling desorption rate.

Crystal structure and morphology control of calcium oxalate using biopolymeric additives in crystallization

Using the acid-rich polymeric additives, poly- l-aspartate (polyD), poly- l-glutamate (polyE), and polyacrylate (polyAA), the structure and morphology of calcium oxalate crystals were controlled during crystallization. In crystallization without the polymeric additives, twinned calcium oxalate monohydrate (COM) crystals were preferentially produced. However, the structural shift of calcium oxalate from a monohydrate (COM) to a dihydrate (COD) form occurred gradually when increasing the polymeric additive concentration, then COD crystals were exclusively crystallized beyond certain critical concentrations of the additives. These critical concentrations actually depended on the molecular configurations of the additives that determined the capability to control the crystallization. When increasing the additive concentration far beyond the critical level, shape modifications without structural changes occurred from a normal octahedral shape (bi-pyramid) to a rod shape (elongated octahedral shape), followed by a dumbbell shape, and finally a sphere shape. Due to its high binding affinity to the crystal surface, polyAA exhibited the most effective elongation in the [0 0 1] direction and clearest development of {1 0 0} faces, while polyE had the least effect on the crystals.

Modifications on the morphology of synthetically-grown calcium oxalate crystals by crystal-associated proteins isolated from bean seed coats ( Phaseolus vulgaris)

Higher plants form crystals of calcium oxalate in well-controlled conditions. This control is performed in specialized cells by an organic matrix composed by soluble and insoluble water macromolecules. The water-soluble protein matrix associated with the calcium oxalate crystals from bean seed coat ( Phaseolus vulgaris) contains many polypeptides of different molecular masses. In this study, we observed that the water-soluble matrix macromolecules strongly inhibited the nucleation of calcium oxalate crystals (this inhibition was concentration dependent). Additionally, two proteins were isolated and purified from the water-soluble matrix with masses of 250 kDa called calcium oxalate macromolecule associated 1 (COMA1) and 27 kDa called calcium oxalate macromolecule associated 2 (COMA2). These proteins were also strong inhibitors of the nucleation of calcium oxalate monohydrate. On the other hand, we found that the modification in the morphology of calcium oxalate crystals due to the presence of water-soluble macromolecules (altogether) affected mainly the {1 2 0} face. Particularly, COMA1 and COMA2 separately had the same influence on the morphology of these crystals.

Calcium oxalate crystal morphology: influence of phospholipid micelles with compositions based on each leaflet of the erythrocyte membrane

Because phospolipids appear to be involved in kidney stone formation, we investigated in vitro calcium oxalate crystal formation in the presence of micelles corresponding to the phospholipid content in the cytoplasmic and exoplasmic leaflets of the plasma membrane. For these studies, we used values for phospholipid composition in human red blood cells as a model system. Distinct morphological and particle number concentrations were observed with these and phosphatidylcholine micelles as well. The relationship of these observations to mechanisms of crystal-membrane interactions and possible early steps in kidney stone formation are discussed.

Scanning Electron Microscopic Study of the Effect of Citrate and Pyrophosphate on Calcium Oxalate Crystal Morphology

The effects of citrate and pyrophosphate on the morphology of calcium oxalate monohydrate crystals formed in a supersaturated calcium oxalate solution were examined by scanning electron microscopy. Within the normal range of urinary concentrations, citrate and pyrophosphate affected the morphology of the crystals. The length/width ratio of the crystals decreased at higher concentrations of citrate and pyrophosphate. Citrate seems to have a dual mechanism of inhibition of crystal growth (binding to the crystal surfaces) and of complexation (with calcium in the solution). Pyrophosphate is believed to bind preferentially to calcium in the solid phase rather than in the solution phase, as it affected crystal morphology at very low concentrations and was detected on the crystals by X-ray microanalysis. Pyrophosphate seems to bind to the monohydrate but not to the dihydrate.