Nano-sized Hydroxyapatite Powders Research Articles

XRD, AFM, IR and TGA study of nanostructured hydroxyapatite

In this work, the synthetic hydroxyapatite (HAP) was studied using different preparation routes to decrease the crystal size and to study the temperature effect on the HAP nano-sized hydroxyapatite crystallization. X-ray diffraction (XRD) analysis indicated that all samples were composed by crystalline and amorphous phases . The sample with greater quantity of amorphous phase (40% of total mass) was studied. The nano-sized hydroxyapatite powder was heated and studied at 300, 500, 700, 900 and 1150 °C. All samples were characterized by XRD and their XRD patterns refined using the Rietveld method. The crystallites presented an anisotropic form, being larger in the [001] direction. It was observed that the crystallite size increased continuously with the heating temperature and the eccentricity of the ellipsoidal shape changed from 2.75 at 300 °C to 1.94, 1.43, 1.04 and 1.00 respectively at 500, 700, 900 and 1150 °C. In order to better characterize the morphology of the HAP the samples were also examined using atomic force microscopy (AFM), infrared spectrometry (IR) and thermogravimetric analysis (TGA).

Mechanochemical Synthesis of Nanosized Hydroxyapatite Powder and its Conversion to Dense Bodies

In this work, nanosized hydroxyapatite (HA) powder was synthesized via mechanochemical method by a dry mixture of calcium hydroxide Ca(OH)2 and di-ammonium hydrogen phosphate (NH4)2HPO4 powders. The effect of mechanochemical process on powder properties was investigated. Three rotation speeds of 170 rpm, 270 rpm and 370 rpm were chose with 15 hours milling time respectively. Characterization of nanopowders was accomplished by Fourier transform infra red (FTIR), X-ray diffraction (XRD) and nanosizer analysis. The green compacted powders with 200 MPa isostatically pressed were prepared and sintered in atmosphere condition at various temperatures ranging from 1150oC - 1350oC. The results showed that the rotation speed affected the obtained powders where the crystallite size was found increased with rotation speed (9 – 21 nm). In contrast, the particle size distribution decreased with rotation speed (322-192 nm). The sintering process has influenced the stability of powder by yielding TCP phase at a lower sintering temperature, 1150oC. However, powder synthesized at 370 rpm has showed a significant hardness, 5.3 GPa after compacted and sintered at 1250oC with the relative density of 95%. This phenomenon is believed to be related with the nanosize powder synthesized at high speed which has contributes the high strength of the sintered bodies.

Synthesis of spherical hydroxyapatite granules with interconnected pore channels using camphene emulsion

The aim of this study was to fabricate porous spherical hydroxyapatite (HA) granules with interconnected pore channels for use as a bone graft substitute. Various weights of camphene porogen were mixed with nano-sized HA powder (camphene/HA = 0, 10, 30, 50, 70, and 90% w/w) and 10% gelatin aqueous solution then added to the mixture. The water-in-oil emulsion method was employed to obtain spherical-shaped granules, of which those 1000-2000 μm in diameter were selectively classified using a standard sieve set. Thermogravimetric analysis and X-ray diffraction were used to determine optimal sintering conditions. The sintered granules were characterized using field emission-scanning electron microscopy (FE-SEM), microcomputed tomography, and porosimetry. The pore size and porosity of spherical HA granules increased with the addition of camphene. Granules with a HA/camphene ratio of 90% (HG90) demonstrated macropores (>50 μm) with interconnected pore channels (porosity: 58.49%). In addition, FE-SEM examination of HG90 coated with polycaprolactone showed that the granule may hold promise as a drug delivery carrier. We concluded that these HG90 granules merit consideration as a bone graft substitute or drug delivery carrier in bone tissue engineering.

Microstructure in Pressureless-Sintered Iron-Containing Hydroxyapatite/Titanium Composites

Pure hydroxyapatite (HA) is brittle and it cannot be directly used for the load-bearing biomedical applications. Aim of this paper was to present a new iron-containing hydroxyapatite/titanium composites synthesized via pressureless sintering at a relatively low temperature of 1000°C using nano-sized HA powders and Ti-33%Fe mixed powders. The microstructure and composition of the new type composites were evaluated. The results showed that the uniformly distributed reinforcing particles had a unique and favorable core/shell microstructure after sintering that consisted of outer titanium and inner iron. The mechanism for the formation of the core/shell structure was discussed. The addition of iron reduced the decomposition rate of HA and the interaction between HA and titanium.

Biochemical Characterization of the Cell-Biomaterial Interface by Quantitative Proteomics

Surface topography and texture of cell culture substrata can affect the differentiation and growth of adherent cells. The biochemical basis of the transduction of the physical and mechanical signals to cellular responses is not well understood. The lack of a systematic characterization of cell-biomaterial interaction is the major bottleneck. This study demonstrated the use of a novel subcellular fractionation method combined with quantitative MS-based proteomics to enable the robust and high-throughput analysis of proteins at the adherence interface of Madin-Darby canine kidney cells. This method revealed the enrichment of extracellular matrix proteins and membrane and stress fibers proteins at the adherence surface, whereas it shows depletion of extracellular matrix belonging to the cytoplasmic, nucleus, and lateral and apical membranes. The asymmetric distribution of proteins between apical and adherence sides was also profiled. Apart from classical proteins with clear involvement in cell-material interactions, proteins previously not known to be involved in cell attachment were also discovered.

Synthesis of nano-sized hydroxyapatite powders through solution combustion route under different reaction conditions

Calcium hydroxyapatite, Ca10(PO4)6(OH)2 (HAp) was synthesized by combustion in the aqueous system containing calcium nitrate–diammonium hydrogen orthophosphate with urea and glycine as fuels. These ceramics are important materials for biomedical applications. Thermo-gravimetric and differential thermal analysis were employed to understand the nature of synthesis process during combustion. Effects of different process parameters namely, nature of fuel (urea and glycine), fuel to oxidizer ratio (0.6–4.0) and initial furnace temperature (300–700 °C) on the combustion behavior as well as physical properties of as-formed powders were investigated. A series of combustion reactions were carried out to optimize the reaction parameters for synthesis of nano-sized HAp powders. The combustion temperature (Tf) for the oxidant and fuels were calculated to be 896 °C and 1035 °C for the stoichiometric system of urea and glycine respectively. The stoichiometric glycine–calcium nitrate produced higher flame temperature (both calculated and measured) and powder with lower specific surface area (8.75 m2/g) compared to the stoichiometric urea–calcium nitrate system (10.50 m2/g). Fuel excess combustion in both glycine and urea produced powders with higher surface area. Nanocrystalline HAp powder could be synthesized in situ with a large span of fuel to oxidizer ratio (φ) in case of urea system (0.8 < φ < 4) and (0.6 < φ < 1.5) for the glycine system. Calcium hydroxyapatite particles having diameters ranging between 20 nm and 120 nm could be successfully synthesized through optimized process variable.

Electrophoretic Deposition of Biocomposite Lignin/Hydroxyapatite Coatings on Titanium

In this work, electrophoretic deposition (EPD) was applied to obtain novel hydroxyapatite (HAP)/lignin (Lig) biocomposite coatings on titanium substrate. Nanosized hydroxyapatite powder, prepared by using the modified chemical precipitation method, was used for the fabrication of HAP/Lig composite coatings. EPD was performed at different values of constant voltage and constant deposition time. It was confirmed that control over deposited mass can be achieved by applied voltage and time. The uniform and compact coatings were successfully deposited at applied voltage of 60 V in various deposition times lower than 1 minute. The effect of lignin as natural non-toxic polymer on microstructure, morphology and thermal behavior of biocomposite HAP/Lig coatings was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The electrophoretically deposited HAP/Lig coating has been successfully sintered at lower sintering temperature of 900°C, producing non-fractured coating and indicating that lignin may exhibit adhesive role, strengthening the bonding between HAP particles and substrate surface.

Microwave sintering of fine grained HAP and HAP/TCP bioceramics

The effect of microwave sintering conditions on the microstructure, phase composition and mechanical properties of materials based on hydroxyapatite (HAP) and tricalcium phosphate (TCP) was investigated. Fine grained monophase HAP and biphasic HAP/TCP biomaterials were processed starting from stoichiometric and calcium deficient nanosized HAP powders. The HAP samples microwave (MW) sintered for 15 min at 900 °C, with average grain size of 130 nm, showed better densification, higher density and certainly higher hardness and fracture toughness than samples conventionally sintered for 2 h at the same temperature. By comparing MW sintered HAP and HAP/TCP samples, it was concluded that pure HAP ceramics have superior mechanical properties. For monophase MW sintered HAP samples, the decrease in the grain size from 1.59 μm to 130 nm led to an increase in the fracture toughness from 0.85 MPa m 1/2 to 1.3 MPa m 1/2.

Protein expression profiles in osteoblasts in response to differentially shaped hydroxyapatite nanoparticles

The use of synthetic hydroxyapatite as bone substitute calls for the knowledge of the influence on adjacent cells. The aim of this study was to investigate the proteins with differential protein expression levels in the proteome of human osteoblast cell line incubated separately with various nano sized hydroxyapatite powders with different shapes and chemical compositions using iTRAQ-coupled 2D LC-MS/MS approach. In the present study, we investigated several intracellular signaling molecules involved in calcium regulation to analyze how osteoblast cells respond to dissimilar HA nanoparticles. It was found there was a significant decrease in cell population after adding the HA nanoparticles to the osteoblasts. Our results combining proteomics analysis and RT-PCR validation on targeted genes involved in calcium regulation confirmed the differences in the cellular response to dissimilar HA nanoparticles.

Synthesis of hydroxyapatite coatings on metal substrates using a spincasting technique

Hydroxyapatite coatings on stainless steel substrates were prepared by a simple spincasting technique. Nanosized hydroxyapatite powders were prepared by precipitating in an electrolytic suspension, and then added to a polylactic acid solution for spincasting. The polylactic acid gave enhanced protection from corrosion and inhibited decomposition of the hydroxyapatite coating during the sintering process in air, a significant advantage over other solution processing techniques. Characterization of the phase composition and morphology of the fabricated films on stainless steel was accomplished by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy.

Characteristics of size controlled hydroxyapatite powders with nanometer size prepared by flame spray pyrolysis

Size controlled hydroxyapatite powders with nanometer sizes were directly prepared by high temperature flame spray pyrolysis. Nanosized hydroxyapatite powders were formed from the evaporated vapors by chemical vapor deposition process. The composition ratio of calcium and phosphorous components was 1.67. The mean size of the hydroxyapatite powders increased from 21 to 81 nm when the concentration of spray solution was changed from 0.05 to 2 mol/L. Sintering of the nanosized hydroxyapatite powders occurred at a temperature of 1000°C, and grain growth increased with increasing the sintering temperatures. The mean grain sizes of the pellets sintered at temperatures of 1200, 1300, and 1400°C were 0.93, 4.9, and 18 μm.

Pressing and sintering of nanosized hydroxyapatite powders

The paper examines the compactability and sintering of nanosized synthetic hydroxyapatite (HA) powders for increasing the durability and strength of HA ceramics. The granulation of HA powders and limitation of the applied pressure prevent delamination in pressing. Porous HA samples show homogeneous nanoporous structure, high compactability, and excellent sinterability, which is better than that of nanosized powders.

Nanosized Hydroxyapatite Powder Synthesized from Eggshell and Phosphoric Acid

The present research describes synthesis of highly sinterable, nano-sized hydroxyapatite (HAp) powders using a wet chemical route with recycled eggshell and phosphoric acid as calcium and phosphorous sources. The raw eggshell was easily turned to CaO by the calcining process, and phosphoric acid was mixed with the calcined eggshell by the wet, ball-milling method. The crystalline development and microstructures of the synthesized powders and sintered samples were examined by X-ray diffractometry and scanning electron microscopy, respectively. The observed phases on the powder synthesis process were dependent on the mixing ratio (wt%) of the calcined eggshell to phosphoric acid and the heating temperature. The ball-milled, nano-sized HAp powder, which has an average particle size of 70 nm, was fully densified at 1300 degrees C for 1h. The Ca/P ratio for stoichiometric composition of HAp was controlled by adjustment of the mixing ratio.

Controlling the Reactivity of Calcium Phosphate Cements

The effect of composition on the reactivity of a calcium phosphate cement (CPC) made of tricalcium phosphate (TCP) – water mixtures was investigated by isothermal calorimetry at 37°C. The parameters of interest were the mean particle size of the powder, the use of small amounts of nanosized hydroxyapatite powder, and the phosphate concentration and the pH of the aqueous solution. The results could be well explained by theoretical considerations. The main parameter controlling CPC reactivity was TCP particle size.

Nano-sized hydroxyapatite powders prepared by flame spray pyrolysis

Nano-sized hydroxyapatite (HAp) powders with high crystallinity and appropriate stoichiometry were prepared by high-temperature flame spray pyrolysis process from the spray solutions with polyethylene glycol (PEG). The mean sizes of the HAp powders obtained from the spray solutions with PEG were changed from several tens to several hundreds nanometers according to the concentrations of PEG added to the spray solutions at a post-treatment temperature of 800 °C. In the TEM-EDX spectrum, the composition ratio of calcium and phosphorous components was 1.69. The HAp powders post-treated at a low temperature of 400 °C had fiber-like morphology. On the other hand, the post-treated HAp powders at temperatures of 600 and 1000 °C had each rod-like morphology with low aspect ratio and spherical-like morphology. The mean sizes of the HAp powders post-treated at temperatures of 600 and 1000 °C were each 32 and 213 nm.

Fabrication of nanostructured hydroxyapatite and analysis of human osteoblastic cellular response

Nano-sized hydroxyapatite (HA) powders were produced by a hydrothermal method and a precipitation method. Spark plasma sintering (SPS) was used to fabricate nanostructured HA (NHA) using nano-sized HA powders as a precursor. Conventional sintering was employed to produce microstructured HA (MHA). Characteristics of HA powders and HA bulk ceramics after sintering were investigated by XRD, FTIR, SEM, TEM, particle size distribution, and AFM. Dense compacts consisting of equiaxed grains with an average grain size of approximately 100 nm were obtained by SPS. Human osteoblasts were cultured on both NHA and MHA and cell attachment, proliferation, and mineralization were evaluated. After 90 min incubation, the cell density on NHA surface was significantly higher than that of MHA and glass control, whereas average cell area of a spread cell was significantly lower on NHA surface compared to MHA and glass control after 4 h incubation. Matrix mineralization was determined after 7 and 14 days incubation by using alizarin red assay combined with cetylpyridinium chloride extraction. NHA shows significant enhancement (p < 0.05) in mineralization compared to MHA. Results from this study suggest that NHA may be a much better candidate for clinical use in terms of bioactivity.

Sol-Gel Synthesis and Characterisation of Nano-sized Hydroxyapatite Powders and Hydroxyapatite/ Poly(D,L-lactide-co-glycolide) Composite Scaffolds

Nano-sized hydroxyapatite (NHA) powders were prepared from calcium nitrate Ca(NO3)2•4H2O and phosphorus pentoxide using a sol–gel approach. The effects of processing parameters on the composition granularity, and morphologies of hydroxyapatite powders were investigated by thermo-gravimetry/differential scanning calorimetry, X-ray diffraction Fourier Transform-infrared spectroscopy, laser particle analysis and transmission electron microscopy. High purity HA powders with particle size of 30–100 nm were obtained by calcining HA gel at 600 °C. The granularity had a narrow distribution and the particles were dispersed well at 600 °C. Hydroxyapatite/poly(D,L-lactide-co-glycolide) (NHA/PLGA) composite scaffolds were prepared by thermally induced phase separation. The compressive strength and water absorption of the scaffolds were investigated. Their mechanical strength increased significantly with the addition of NHA. The composites with 25 wt.% of NHA exhibited good mechanical properties with an average compressive strength of 2.53 MPa. The hydrophilicity increased with the addition of NHA too. NHA/PLGA scaffolds could be a candidate for tissue engineering.

마이크로파-수열 합성법을 이용한 나노 수산화아파타이트 합성과 특성평가

Nano-sized hydroxyapatite (HAp) powders were synthesized by a microwave-hydrothermal method using H₃PO₄ and Ca(OH)₂ as starting materials. The applied microwave powers and mole ratio of Ca/P were served as powerful factors in the synthesis of calcium phosphate. In the case of relatively low microwave power of 450 W and Ca/P ratio of 1.57, the mixed calcium phosphate compounds were detected in the synthesized powders. But in the case of running at 550 W and 1.67(Ca/P), the synthesized powder showed the monophase of HAp having two kinds of morphologies. One was a needle shape with 5~15 ㎚ in width and 20~50 ㎚ in length, and the other was a spherical shape of 10~40 ㎚ in diameter.

Synthesis of high purity nano-sized hydroxyapatite powder by microwave-hydrothermal method

Nano-sized hydroxyapatite (HAp) powders were synthesized by a microwave-hydrothermal method using H 3PO 4 and Ca(OH) 2 as starting materials in a closed-vessel microwave device at 600 psi and 300 °C for 30 min. The applied microwave powers and mole ratio of Ca/P served as powerful factors in the synthesis of calcium phoaphate. In the case of relatively low microwave power of 450 W and Ca/P ratio of 1.57, mixed calcium phosphate compounds such as Ca(OH) 2, CaHPO 4 and HAp were detected in the synthesized powders. But in the case of running at 550 W, 1.67, synthesized powder showed the monophase of HAp having two kinds of morphologies. One was a needle shape with 4–15 nm in width and 20–50 nm in length, and the other was a spherical shape of 10–30 nm in diameter. The purity of nano-sized HAp powder was determined as 99.995% by ICP-MS.

High-Pressure and -Temperature Sintering of Nanosized Hydroxyapatite Powders

High-Pressure and -Temperature Sintering of Nanosized Hydroxyapatite Powders