HAp Content Research Articles

Influence of experimental parameters on spatial phase distribution in as-sprayed and incubated hydroxyapatite coatings

In the present study, the behavior and properties of plasma-sprayed hydroxyapatite coatings [Ca(10)(PO(4))(6)(OH)(2), HAp] were investigated in relation to the spraying process. The experiments were focused on the influence of type of feedstock and spray power on the phase composition and distribution within the coatings. Depth profiles of the coatings were investigated before and after incubation in revised simulated body fluid (SBF) by X-ray diffraction and infrared spectroscopy. Besides HAp, the coatings contain oxyapatite (OAp) and carbonate apatite (CAp). Additionally, tricalcium phosphate (TCP), tetracalcium phosphate (TTCP), CaO, and an amorphous phase were detected in the coatings. The HAp content directly depends on the used spray powder and spray power, where the influence of spray powder is much higher than the influence of the spray power. The grain size range of the spray powder strongly influences the HAp content in the coating and the formation of CaO. The in vitro behavior of the coatings in simulated body fluid mainly depends on the contents of CaO and amorphous calcium phosphate, respectively. The formation of portlandite due to the reaction of the coating with the SBF is strongly influenced by the porosity of the coatings and can be used as an indicator for the depth of interaction between fluid and coating.

Thermal properties and flame retardancy of polycarbonate/hydroxyapatite nanocomposite

AbstractThe thermal degradation of polycarbonate (PC) and polycarbonate/hydroxyapatite (PC/HAP) composite was investigated by the thermogravimetric analysis (TGA) and the decomposition activation energy was calculated by Kissinger method. It was found that the first step decomposition activation energy (Ea1) was higher than that of pure PC while the second step decomposition (Ea2) decreased a little. The limiting oxygen index (LOI) of PC/HAP composite with 0.5 wt % HAP reached 34. The carbon char of PC and PC/HAP composite after combustion was analyzed by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and flourier transform infrared spectroscopy (FTIR) and similar morphology, components, and the same functional groups were found in the char residues. Based on these results, it can be concluded that a low content of HAP in PC matrix can significantly improve the thermal properties and flame retardancy of the composite. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Preparation and lead ion removal property of hydroxyapatite/polyacrylamide composite hydrogels

We report the synthesis of hydroxyapatite/polyacrylamide (HAp/PAAm) composite hydrogels with various HAp contents by free radical polymerization and their removal capability of Pb 2+ ions in aqueous solutions with controlled initial Pb 2+ ion concentrations and pH values of 2–5. The swelling ratio of the composite gels in aqueous solutions decreases with increasing the HAp content in the gels. The composite gel with higher HAp content exhibits the higher removal capacity of Pb 2+ ions owing to the higher adsorption sites for Pb 2+ ions, but shows the slower removal rate of Pb 2+ ions due to the lower degree of swelling. The removal mechanism of Pb 2+ ion is very sensitive to the pH value in aqueous solution, although the removed amount of Pb 2+ ion is nearly same, regardless of pH values of 2–5. The removal mechanism, the dissolution of HAp in the composite gel and subsequent precipitation of hydroxypyromorphite (HPy), is dominant at lower pH 2–3, whereas the mechanism, the adsorption of Pb 2+ ions on the composite gel and following cation exchange reaction between Pb 2+ ions adsorbed and Ca 2+ of HAp, is dominant at higher pH 4–5. The equilibrium removal process of Pb 2+ ions by the composite gels at pH 5 is described well with the Langmuir isotherm model. The equilibrium removal capacities of the composite gels with 30, 50, and 70 wt.% HAp contents are evaluated to be 123, 178, and 209 mg/g, respectively.

Optimized bone regeneration based on sustained release from three‐dimensional fibrous PLGA/HAp composite scaffolds loaded with BMP‐2

Contemporary treatment of critical bone defect remains a significant challenge in the field of orthopedic surgery. Engineered biomaterials combined with growth factors have emerged as a new treatment alternative in bone repair and regeneration. Our approach is to encapsulate bone morphogenetic protein-2 (BMP-2) into a polymeric matrix in different ways and characterize their individual performance in a nude mouse model. The main objective of this study is to examine whether the PLGA/HAp composite fibrous scaffolds loaded with BMP-2 through electrospinning can improve bone regeneration. The hypothesis is that different loading methods of BMP-2 and different HAp contents in scaffolds can alternate the release profiles of BMP-2 in vivo, therefore modify the performance of scaffolds in bone regeneration. Firstly, mechanical strength of scaffolds and HAp nanoparticles distribution in scaffolds were investigated. Secondly, nude mice experiments extended to 6 weeks were carried out to test the in vivo performance of these scaffolds, in which measurements, like serum BMP-2 concentration, ALP activity, X-ray qualification, and H&E/IHC tissue staining were utilized to monitor the growth of new bone and the changes of the corresponding biochemical parameters. The results showed that the PLGA/HAp composite scaffolds developed in this study exhibited good morphology/mechanical strength and HAp nanoparticles were homogeneously dispersed inside PLGA matrix. Results from the animal experiments indicate that the bioactivity of BMP-2 released from the fibrous PLGA/HAp composite scaffolds is well maintained, which further improves the formation of new bone and the healing of segmental defects in vivo. It is concluded that BMP-2 loaded PLGA/HAp composite scaffolds are promising for bone healing.

Removal of lead ions in aqueous solution by hydroxyapatite/polyurethane composite foams

We have prepared hydroxyapatite/polyurehthane (HAp/PU) composite foams with two different HAp contents of 20 and 50 wt.% and investigated their removal capability of Pb 2+ ions from aqueous solutions with various initial Pb 2+ ion concentrations and pH values of 2–6. HAp/PU composite foams synthesized exhibited well-developed open pore structures which provide paths for the aqueous solution and adsorption sites for Pb 2+ ions. With increasing the HAp content in the composites, the removal capability of Pb 2+ ions by the composite foams increases owing to the higher adsorption capacity, whereas the removal rate is slower due to the less uniform dispersity of HAp in composite foams. The removal rate of Pb 2+ ions is also slower with increasing the initial Pb 2+ ion concentration in aqueous solutions. The removal mechanism of Pb 2+ ion by the composites is varied, depending on the pH value of aqueous solution: the dissolution of HAp and precipitation of hydroypyromorphite is dominant at lower pH 2–3, the adsorption of Pb 2+ ions on the HAp/PU composite surface and ion exchange reaction between Ca 2+ of HAp and Pb 2+ in aqueous solution is dominant at higher pH 5–6, and two removal mechanisms compete at pH 4. The equilibrium removal process of Pb 2+ ions by the HAp/PU composite foam at pH 5 was described well with the Langmuir isotherm model, resulting in the maximum adsorption capacity of 150 mg/g for the composite foam with 50 wt.% HAp content.

Preparation of Macroporous Hydroxyapatite/Chitosan-Alginate Composite Scaffolds for Bone Implants

Porous HAp/chitosan-alginate composite scaffolds were successfully synthesized by insitu co-precipitation method. During the preparation of HAp/chitosan-alginate composite scaffolds, the interaction between chitosan-alginate molecules would be reduced with increasing HAp content, with the resulting that the chitosan-alginate molecules were homogeneously dispersed in the composite scaffolds. The chitosan-alginate content was found to be almost consistent as initially added during the preparation. These results imply that chitosan-alginate was almost perfectly incorporated into the composites. It was found that the pore structure of the composite scaffolds with low HAp content was similar to chitosan-alginate scaffolds, and the morphology of uniform microstructure was unaffected by the presence of HAp. However, the pore diameter decreased with increasing the HAp content up to HAp content of 30 wt%, eventually the pore structure was collapsed and the composites scaffolds appeared to be agglomerated at higher HAp content.

Three‐dimensional fibrous PLGA/HAp composite scaffold for BMP‐2 delivery

A protein loaded three-dimensional scaffold can be used for protein delivery and bone tissue regeneration. The main objective of this project was to develop recombinant human bone morphogenetic protein-2 (rhBMP-2) loaded poly(D,L-lactide-co-glycolide)/hydroxylapatite (PLGA/HAp) composite fibrous scaffolds through a promising fabrication technique, electrospinning. In vitro release of BMP-2 from these scaffolds, and the attachment ability and viability of marrow derived messenchymal stem cells (MSCs) in the presence of the scaffolds were investigated. The PLGA/HAp composite scaffolds developed in this study exhibit good morphology and it was observed that HAp nanoparticles were homogeneously dispersed inside PLGA matrix within the scaffold. The composite scaffolds allowed sustained (2-8 weeks) release of BMP-2 whose release rate was accelerated with increasing HAp content. It was also shown that BMP-2 protein successfully maintained its integrity and natural conformations after undergoing the process of electrospinning. Cell culture experiments showed that the encapsulation of HAp could enhance cell attachment to scaffolds and lower cytotoxicity.

Hydroxyapatite moldable formulation using natural rubber latex as binder

A simple but efficient processing method for shaping intricate bioceramic green bodies has been developed by using natural rubber latex as binder. Different shapes of hydroxyapatite Ca10(PO4)6(OH)2 (HAP) were molded from a composite formulation containing wet precipitated HAP, natural rubber latex (NRL), and a stabilizer. On controlled heat treatment followed by sintering, dense shapes of HAP contours were obtained. The thermal degradation profile of HAP-NRL composites shows that NRL degrades slowly without any abrupt exotherm. The results of energy dispersive X-ray analysis together with inductively coupled plasma (ICP) analysis indicate that the inorganic residue of NRL does not contain any heavy element. The sintered density of the samples increased with increased HAP content in the formulation and percentage shrinkage reduced accordingly. On varying the HAP content in the formulation from 35 to 95 wt %, the compositions with 85, 90, 92, and 95 wt % HAP showed better flexural strength in the range 40-54 MPa and a flexural modulus value in the range 36-50 GPa. The fracture morphology, as observed by the scanning electron microscope confirms that with increased HAP content in the formulation the sample microstructure attains higher uniformity. The Vickers microhardness for the samples sintered at two different temperatures (1150 and 1250 degrees C) showed that hardness increases with increase in the sintering temperature with a maximum for the highest HAP loaded formulation.

Effect of Reaction Conditions on Pore Configuration and Mechanical Property for Porous Hydroxyapatite Prepared by Polymer Sponge Method

Porous HAp scaffolds have been prepared by using the slurry including HAp and magnesia based on the replication of polymer sponge substrate. The influence of HAp and MgO content in slurry on the pore morphology and size, and density, porosity, and mechanical strength of porous HAp scaffolds was investigated. The obtained scaffolds with average pore sizes ranging 150 to 300 μm had open, relatively uniform, and interconnected porous structure regardless of HAp and MgO content. As the MgO content increased, the pore network frame of scaffolds became to be relatively stronger, even though the pore size was not much changed. The compressive strength of the scaffolds increased rapidly with the increase of MgO content at a fixed HAp content because of increasing the pore wall thickness and density of the scaffolds. As a result, the porosity, density, and compressive strength of the porous HAp scaffolds scaffolds prepared by the sponge method were significantly affected by the addition of MgO.

Properties of Hydroxyapatite - Hyaluronic Acid Nano-Composite Sol and its Interaction with Natural Bones and Collagen Fibers

Biocompatible nano-composite sol (NCS) comprising nano-crystalline hydroxyapatite (HAp, Ca 10(PO4)6(OH)2) and hyaluronic acid (HYA) was prepared. By varying the relative content of HAp in NCS, strongest network structure was obtained at 10wt% HAp in NCS, as confirmed from a number of circumstance evidences obtained by rheological, thermoanalytical, crystallographical measurements as well as FT-IR spectra. Interaction of NCS with natural bones and gut strings made from gut collagen was then examined in vitro. Adhesion of the collagen fibers with NCS was observed at the fracture surface of natural bones. Gut collagen was disentangled to the fragments of about 10 nm thick, where no NCS was observed, thus, confirming the fact that the adhesive strength between NCS and bone surface is stronger than that among collagen fibers. suspension of Ca(OH)2 (Wako Chemicals) in the presence of 1.0wt% HYA with respect to the total mass of the mixture. The formulation was set to fix the Ca/P ratio at 1.67, i.e. the stoichiometry of HAp. This gave rise to the sample of the composite with HAp 1.0wt% (sample NCS01). Likewise, we varied the content of HAp to give samples NCS05, NCS10 and NCS15, with their HAp contents 5, 10, and 15 wt%, respectively. 2.2. Characterization of NCS Bulk properties of the nanocomposite sol (NCS) were examined primarily by rheometry, for which we used a coaxial cylindrical rheometer (Haake, Rotovisco, RT 20) at 25°C. Samples were ultrasonically dispersed for 10min immediately before each measurement and preliminarily sheared at 350s -1

Preparation of Bioactive Cellulose/Hydroxyapatite Composite Tapes

A composite material consisting of cellulose and HAp was prepared using coagulation of a native cellulose suspension. Composite tapes with a HAp content below 50 vol.% exhibit a gradient of filler particles across the cross-section of the sample due to gravity force that causes sedimentation of HAp, as long as the viscosity of the suspension is below a critical level during the coagulation process. According to gravimetric and solution analysis as well as SEM, the filler content influences the amount and uniformity of HCA precipitated in the surface of the tape. With increasing content of filler in the cellulose matrix, the apatite growth from SBF is promoted, due to a higher amount of HAp particles that serve as nucleation sites.

Porous alginate/hydroxyapatite composite scaffolds for bone tissue engineering: preparation, characterization, and in vitro studies.

In this study a series of alginate/hydroxyapatite (HAP) composite scaffolds was prepared by phase separation. HAP was incorporated into the alginate gel solution to improve both the mechanical and cell-attachment properties of the scaffolds. These scaffolds had a well-interconnected porous structure with an average pore size of 150 microm and over 82% porosity. The alginate/HAP scaffold prepared at -40 degrees C with a 50% HAP content showed the best mechanical properties. The morphology of scaffolds could be manipulated by tuning the quenching temperature during the preparation. The dissolution of alginate/HAP composite scaffolds could be slowed by the pretreating them by immersion in 1.0 M CaCl(2) solution. The rat osteosarcoma UMR106 cells, an osteoblastic cell line, seeded in the scaffolds, displayed better cell attachment to the 75/25 and 50/50 alginate/HAP composite scaffolds than to the pure alginate scaffold. The natural polymeric sponges that fabricated in this study may be a promising approach for tissue-engineering applications.

Biodegradable and biocompatible nanocomposites of poly(ϵ‐caprolactone) with hydroxyapatite nanocrystals: Thermal and mechanical properties

AbstractNanocomposites of poly(ϵ‐caprolactone) (PCL) with hydroxyapatite nanocrystals (HAP) prepared through the solvent‐cast technique were characterized by means of transmission electron microscopy (TEM), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile tests. Such composites are of great importance to make bone‐like substitutes as HAP nanocrystals have similar composition, morphology, and crystal structure as natural apatite crystals. The TEM micrograph reveals the nanocrystals dispersed homogeneously in the matrix at a microscale level. The solvent‐cast samples commonly show much higher melting points and crystallinity than the melt‐quenched samples, due to a lower undercooling as well as more sufficient time to crystallize. For both cases of samples, the melting point decreases slightly with HAP content while the level of crystallinity attained by the PCL component is not hindered by the nanocrystals. Both the glass transition temperatures and the nonisothermal crystallization temperatures are composition dependent. The tensile modulus increases with increasing HAP content while the yield stress is almost invariant with composition. Theoretical prediction of the modulus based on Halpin–Tsai equations shows excellent agreement with the experimental result. By analysis of the variation in fracture stress and strain with composition, a ductile‐to‐quasi‐brittle transition is revealed to be operative for the nanocomposites, as also can be seen by SEM. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 676–683, 2002

Functionally graded Ti/HAP coatings on Ti–6Al–4V obtained by chemical solution deposition

Graded Ti 100− x /HAP x ( x=0 – 100%) films were prepared on Ti–6Al–4V implants by chemical solution deposition using a titanium-isopropoxide chelated by acetylacetone, calcium nitrate and phosphoric acid as starting materials. Ti/HAP solutions with variable HAP contents from 0 to 100% at 10% intervals were spin coated on the substrates and prefired at 500 °C. X-ray diffraction and field emission-scanning electron microscope analysis showed that Ti/HAP coatings were obtained with a dense interface between coating and substrate by final annealing at 500 °C and higher. The effectiveness of the functionally graded HAP/Ti coatings was discussed based on the analysis of the variation of Ca and P contents in simulated body fluid as a function of annealing temperature.

Petal-like apatite formed on the surface of tricalcium phosphate ceramic after soaking in distilled water

In the present study six types of tricalcium phosphate ceramic were prepared and soaked in distilled water for different periods to investigate whether a surface apatite layer was formed on TCP ceramics or not. X-ray diffractometry (XRD) and Fourier-transformed infrared (FTIR) spectrometer were used to examine the changes in crystalline phases and functional groups of TCP ceramics for different soaking periods. Calcium and phosphate ions released from TCP ceramics during soaking were recorded by atomic absorption analysis and ion-coupled plasma. Results revealed that αTCP, αTCP/ βTCP mixture ( αβTCP) and βTCP ceramic were gradually dissolved. There was no apatite layer formed on their surface after being immersed in distilled water for different durations of time. Mg-TCP ceramic, tricalcium phosphate doped with Mg ions, exhibited a lower dissolution rate than the other types of TCP ceramics. Apatite crystals were also not formed on the surface of Mg-TCP ceramic when immersed in distilled water. Tribasic calcium phosphate, prepared from wet precipitation method, was converted to βTCP/HAP (H βTCP) or αTCP/ βTCP/HAP (H αβTCP) crystalline composition at different sintering temperatures (1150°C and 1300°C). The surface apatite layer did not appear on H βTCP ceramic after soaking. We observed that petal-like apatite was formed on the H αβTCP ceramic surface after being immersed for 2 weeks. αTCP phase of H αβTCP ceramic was not directly converted to apatite during soaking. The surface apatite layer formed on the H αβTCP ceramic surface was due to the precipitation of the calcium and phosphate ions released from αTCP dissolution. HAP, which existed in the structure of H αβTCP ceramic, plays a role as apatite-precipitating seed to uptake calcium and phosphate ions. TCP ceramics which lacked αTCP and HAP content neither converted to apatite nor formed surface apatite on their surfaces during immersion.

Analyse par chromatographie liquide du diamino-2,3 phénazine et de l'hydroxy-2 amino-3 phénazine dans les carbendazimes techniques et formulés

Determination by liquid chromatography of 2,3-diaminophenazine and 2-hydroxy-3-aminophenazine in technical and formulated carbendazims 2,3-Diaminophenazine (DAP) and 2-hydroxy-3-aminophenazine (HAP) are highly mutagenic compounds that can be formed during the synthesis of carbendazim. A method has been developed to determine the DAP and HAP contents of technical and formulated carbendazims. The method is simple, rapid (20 min) and minimizes the degradation of phenazines is olution. All of the analyzed technical products (14) contained DAP, but only three wettable powders, among the twelve formulations analyzed, gave a result above the detection limit. HAP could be detected in none of the samples.

Storage reliability with periodic test : Eugene C. Martinez. Proc. a. Reliab. Maintainab. Symp. 181 (1984)

As an environmentally-friendly construction technique, modern rammed earth stabilized with Portland cement has attracted growing interest recently. Some organic clays with high water content are used to prepare self-compacting poured earth in South China. In this study, cement-based composites (CSCN) were employed to substitute Portland cement, and the influence of organic matter (humic acid powder, HAP) on strength development of self-compacting poured earth was investigated using reconstituted organic clay by unconfined compressive strength (UCS) test, X-ray diffraction (XRD) and scanning electron microscope (SEM). Due to the reduction of hydration products by adding HAP, the contribution of HAP was regarded as the consumption of CSCN and the quantitative analysis of consumption effect defined as consumption index (OCI) was investigated by the clay-water/CSCN ratio hypothesis. The interrelationship of OCI to curing time and the mathematical models for predicting the compressive strength of CSCN stabilized self-compacting poured earth with any HAP content were proposed. It was observed that the OCI values decreased with the increase of CSCN content and curing time. The precisions of consumption index and strength prediction models were verified by comparing predicted results and experimental results, and their deviation was mostly within 10%. The influence of HAP on phase changes in stabilized self-compacting poured earth was confirmed by XRD and SEM-EDS analysis, and the amounts of hydration products decreased significantly as increasing the HAP content.