Morphology Of Hydroxyapatite Crystals Research Articles

Hydroxyapatite formation from calcium carbonate single crystal under hydrothermal condition: Effects of processing temperature

Hydrothermal processing has been used for synthesis of hydroxyapatite (HAp) crystals with unique morphologies. Our previous studies reported that the morphology of HAp was affected by dissolution behavior of starting materials under a hydrothermal condition. In this study we evaluated the effects of processing temperature on formation and morphology of HAp crystals under a hydrothermal condition. Calcite (CaCO3) single crystal as a starting material was hydrothermally treated in a phosphate solution at various temperatures. After hydrothermal processing for 24h, needle-shaped HAp crystals formed on the surfaces of all the samples. The size of HAp crystals increased with increasing the processing temperature. Plate-shaped HAp was observed on the cross-section of the starting material treated at 200°C. The structure of HAp plates were generated by arrangement of needle-shaped HAp crystals during their crystal growth. The difference in the processing temperature affects the morphology and structure of HAp formed on the starting material under the hydrothermal condition.

Control of hydroxyapatite crystal growth by gallic acid.

The purpose of this study is to detect the effect of gallic acid (GA) on hydroxyapatie crystal growth and find the mechanism of the regulation. We evaluated the morphology of HAP crystals grown under various amounts of GA (0, 0.05, 1, and 4 gL(-1)). Subsequently, the chemical composition, crystal size and the morphology were investigated via the energy-dispersive X-ray spectrometer, attenuated total fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction analysis, transmission electron microscope and scanning electron microscopy. In all groups, the Ca/P ratio was closed to 1.67. In the absence of GA, crystals did not arrange, while in the presence of GA, crystals tended to form spherules. The size of the crystals decreased with the concentration of GA increased. These results indicated the role of GA on the growth and morphology of hydroxyapatite crystals, which might be the key mechanism for gallic acid regulating the mineralization.

Temperature Effect on Hydroxyapatite Preparation by Co-precipitation Method under Carbamide Influence

Hydroxyapatite crystal was prepared by homogeneous co-precipitation method using a mixture of Calcium nitrate and diammonium phosphate as raw materials and carbamide as the buffering agent. To analyzed the influence of temperature on hydroxyapatite crystal morphology, the phase composition, crystal morphology and growth orientation were characterized by X-ray diffraction, scanning electron microscope and infrared spectrum respectively. The results show that when the reaction temperature increase from 70 °C to 95 °C, the phases composition of crystal transform from the two phases of tricalcium phosphate and eight calcium phosphate to hydroxyapatite single crystal; the morphology of the hydroxyapatite crystals transforms from nodular whisker to perfectly and compactly acicular whisker.

Novel apatite-based sorbent for defluoridation: synthesis and sorption characteristics of nano-micro-crystalline hydroxyapatite-coated-limestone.

Elevated levels of fluoride (F(-)) in groundwaters of granitic and basaltic terrains pose a major environmental problem and are affecting millions of people all over the world. Hydroxyapatite (HA) has been shown to be a strong sorbent for F(-); however, low permeability of synthetic HA results in poor sorption efficiency. Here we provide a novel method of synthesizing nano- to micrometer sized HA on the surfaces of granular limestone to improve the sorption efficiency of the HA-based filter. Our experiments with granular limestone (38-63, 125-500 μm) and dissolved PO4(3-) (0.5-5.3 mM) as a function of pH (6-8) and temperature (25-80 °C) indicated rapid formation of nano- to micrometer sized HA crystals on granular limestone with the maximum surface coverage at lower pH and in the presence of multiple additions of aqueous PO4(3-). The HA crystal morphology varied with the above variables. The sorption kinetics and magnitude of F(-) sorption by HA-coated-fine limestone are comparable to those of pure HA, and the F(-) levels dropped to below the World Health Organization's drinking water limit of 79 μM for F(-) concentrations commonly encountered in contaminated potable waters, suggesting that these materials could be used as effective filters. Fluorine XANES spectra of synthetic HA reacted with F(-) suggest that the mode of sorption is through the formation of fluoridated-HA or fluorapatite at low F(-) levels and fluorite at high F(-) loadings.

Hydrothermal Time Effecting on the Morphology of Hydroxyapatite Templated by L-DOPA

Using Ca(NO3)2·4H2O, (NH4)2HPO4 and ammonia water as the starting raw materials and L-DOAP as template, hydroxyapatite (HAP) crystals were successfully prepared at 180 °C by changing the hydrothermal time. The HAP crystals were characterized by X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (FESEM). The XRD patterns indicate that increasing hydrothermal time is helpful to improve the purity of the product and enhance crystallinity of HAP crystal. The FTIR analysis shows that the carbonate ions enter into the HAP crystal lattice and the final products are carbonate-containing hydroxyapatite. The FESEM images illustrate that HAP crystal morphology changed to flower-like hierarchical structures and grass blanket-like hierarchical structures when increasing the hydrothermal time to 1 h and 24 h. Therefore, hydrothermal time has a great influence on the morphology of HAP and the possible formation mechanism of HAP samples has been discussed.

Hydrothermal synthesis of hierarchical hydroxyapatite: Preparation, growth mechanism and drug release property

Hydroxyapatite (HAP) hierarchical microspheres were synthesized by a facile hydrothermal method using calcium nitrate and ammonium dihydrogen phosphate through controlling complexing agents. The influences of two kinds of complexing agents (potassium sodium tartrate tetrahydrate and trisodium citrate) and reaction time on the morphology of HAP crystals have been investigated. These results indicate that complexing agents have a great influence on the morphology of HAP. When potassium sodium tartrate tetrahydrate was used as complexing agent, HAP flowers were composed of the network of nanosheet building blocks. Well-crystallized HAP dandelions with nanorods radiating from the center can be obtained by the introduction of trisodium citrate. Broader XRD diffraction peaks imply a nanometer scale size. Based on XRD and SEM results, the formation mechanism of HAP crystals has been discussed. The hierarchically structured HAP microspheres were explored as drug carriers. The results indicate that HAP flowers and dandelions showed a favorable sustained release property for ibuprofen; thus, they are very promising for application in drug delivery.

Pressure effecting on morphology of hydroxyapatite crystals in homogeneous system

Using Ca(NO3)2·4H2O, (NH4)2HPO4 and urea as the starting raw materials, hydroxyapatite (HAP) crystals were successfully prepared at low temperature (95 °C) by changing the starting pressure inside the autoclave. The HAP crystals were characterized by XRD, SEM, HRTEM, and FTIR technologies. The XRD patterns indicated that increasing the pressure is helpful to improve the purity of the product and the starting pressure change inside the autoclave has a great effect on the growth of HAP crystal planes. The effect of pressure on the growth of various crystal planes was certified by the analysis of HRTEM micrographs. The SEM images illustrated that HAP crystal morphology changed to long plate-like crystals, hexagonal prism-like crystals, and the crystal flakes from needle-like whiskers when increasing the starting pressure inside the autoclave to 0.5 MPa, 0.9 MPa, 1.1 MPa from 0.11 MPa. The formula (IV) about the growth rate of a-surface and c-surface was presented on the basis of the traditional formula about the growth rate of the polyhedral crystallization and the crystal and the growth unit model. According to the formula (IV), a reasonable interpretation was introduced for pressure effecting on morphologies of HAP crystal.

Effect of poly(sodium 4-styrene-sulfonate) on the crystal growth of hydroxyapatite prepared by hydrothermal method

Hydroxyapatite (HA) crystals with different morphologies were synthesized by hydrothermal method, using Ca(NO 3) 2·4H 2O and (NH 4) 3PO 4·3H 2O as raw materials and poly(sodium 4-styrene-sulfonate) (PSS) as the template. The crystals from above preparation procedure were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscope (FT-IR), transmission electron microscope (TEM), thermogravimetry analyzer (TG) and UV–Vis diffuse reflectance spectra (UV–Vis). The results show that PSS concentration and the hydrothermal temperature play key roles in controlling the morphology of HA crystals. At certain temperature, the obtained HA transformed from fibre-like to rod-like with the increasing of PSS concentration. At certain PSS concentration, the shape of obtained HA varied from rod-like to prism-like when the temperature is increased. And the aspect ratio of HA crystal decreases with the increasing of PSS concentration and hydrothermal temperature. The possible formation mechanism of different morphologies of HA crystals is also discussed in this paper.

In VitroEffects of Cementum Protein 1 (CEMP1) on Calcium Phosphate Crystal Formation and its Role During the Mineralization Process

ABSTRACTCementum contains specific molecules that could serve to identify, isolate and characterize the cementoblast lineage and to determine the cellular and molecular mechanisms that regulate the cementogenesis process, since it plays a key role during the periodontal regeneration process. One of these molecules is the human cementum protein 1 (CEMP1); which has a molecular weight of 25,9 kDa.In vitroexperiments have shown that CEMP1 promotes cellular adhesion and differentiation. In addition, this protein has been implied in regulating the degree of deposition, composition and morphology of hydroxyapatite crystals formed by putative cementoblastin vitro. Therefore, it is possible that CEMP1 promotes the formation, growth and regulates the morphology of hydroxyapatite crystalsin vitro.We have produced a human recombinant CEMP1 (hrCEMP1) in a prokaryotic system. ThehrCEMP1 purification was realized using the column NiTA HisPrep FF/16. Assays of calcium phosphate crystal growth were realized by means of capillary counterdiffusion system. Our results demonstrated thathrCEMP1 promotes octacalcium phosphate crystal nucleation and possesses high affinity for hydroxyapatite. We infer thathrCEMP1 plays a key role during the regeneration of mineralized tissues.

Biomimetic synthesis of micrometer spherical hydroxyapatite with β-cyclodextrin as template

Spherical hydroxyapatite (HA) crystals were prepared successfully with β-cyclodextrin (β-CD) as template by biomimetic method. Their properties were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscope (FTIR), thermogravimetric analyzer (TG), and scanning electron microscope (SEM). The results show that the concentration of β-CD have a significant effect on the morphology of HA crystals. Spherical HA crystals with the diameter of 1.0–3.0 μm can be obtained in the presence of 1.5% β-CD. The obtained crystals are the composites of HA/β-CD. This is a result of the interaction between HA and β-CD.

Chondroitin sulfate template-mediated biomimetic synthesis of nano-flake hydroxyapatite

By Ca(NO 3) 2·4H 2O and (NH 4) 3PO 4·3H 2O as reagents and chondroitin sulfate (ChS) as a template, nano-flake hydroxyapatite (HA) is synthesized using a biomimetic method according to the biomineralization theory. HA crystals obtained are characterized in crystalline phase, microstructure, chemical composition and morphology by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), transmission electron microscopy (TEM) and elemental analysis respectively. UV–vis spectrum is adopted to investigate interactions between functional groups ChS and HA. The results show that HA crystal nucleation and growth take place in chemical interactions between HA crystals and ChS as a template. And elemental analysis indicates that obtained HA contains a small amount of ChS. Furthermore, ChS concentration significantly affects the morphology of HA crystals. Staple-fiber-like HA crystals can be obtained at a low concentration in ChS, and flake-like HA crystals synthesized at a high concentration (≥0.5 wt.%) of ChS as a template.

Effect of Albumin on the Growth Characteristics of Hydroxyapatite Coatings on Alumina Substrates

A potent biomolecule, egg albumin (EA), has been used in the biomimetic coating of hydroxyapatite (HAp) on α‐Al2O3 substrate. The same experiment was repeated without using EA and the results have been compared. In both cases, the substrates were incubated up to 6 days in SBF (simulated body fluid) at 37°C with a periodic replacement by freshly prepared SBF at 48‐h intervals. The presence of EA influenced the growth and morphology of HAp crystals. Without EA, the HAp coating comprises irregular‐shaped, serrated‐edged plates whereas with EA, thick and regular‐edged HAp crystal plates were observed on the α‐Al2O3 substrate.

Influential factors on morphology of hydroxyapatite crystals

Needle-like hydroxyapatite crystals were synthesized by homogeneous precipitation method with water-soluble calcium salts and phosphates. The work focuses on the analysis of influencing factors on length and lengh/diameter ratio of hydroxyapatite crystals, which are main characteristics of reinforcement materials. The effects caused by system temperature, concentration of nutrient, and additives are discussed, and the optimum reacting condition is given.

A molecular tectonics–crystal engineering approach for building organic–inorganic composites. Potential application to the growth control of hydroxyapatite crystals

The effect of bisamidinium type dications as tectons on the crystal formation of hydroxyapatite was investigated. Evidence of the structural interactions between three tectons with different numbers and locations of H-bond donor sites and hydroxyapatite crystals has been shown. Some correlations between the molecular structure of the organic tectons and the morphology of hydroxyapatite crystals were observed. These results may be of interest in the control of hydroxyapatite morphogenesis as well as its surface properties.

Effect of chondroitin sulfate and biglycan on the crystallization of hydroxyapatite under physiological conditions

Crystallization of hydroxyapatite (HA) in collagen gels has been studied in vitro in order to mimic biomineralization under physiological conditions. In particular, the effect of chondroitine sulfate (CS) and biglycan (BG) additions to the gel on the growth kinetics and morphology of HA crystals has been investigated. Large molecules of CS disrupt the gel and lower its viscosity, thus increasing the nucleation and growth rates as well as the overall mass of crystallized HA clusters, while the individual crystallite shape and size (∼1 μm long) remain unchanged. In contrast, the presence of about 100 μg/ml gel of BG limits the crystal size to less than 100 nm, since the protein cores of BG bind to collagen fibers forming a three-dimensional fiber network with a “lattice” constant of about 50 nm. This network provides preferential sites for ordered heterogeneous nucleation and also prevents clustering of HA crystals. Besides the general importance of these results for studying the biomineralization processes, they may explain the apparition of osteoporosis in BG-gene deficient mice.