Porous Spherical Hydroxyapatite Research Articles

A Quick and Convenient Route to Prepare Hydroxyapatite Porous Microspheres

Due to the big specific surface area, good flowability and absorption ability, porous spherical HA materials have received extensive attention of the researchers. However, the facile and convenient synthesis of well-rounded HA microspheres with a porous structure is rarely reported. What’s more, the size of HA microspheres was usually less than 10 μm. In this study, by employing hexamethylenetetramine (HMT) as the pH regulator, hydroxyapatite (HA) microspheres with good uniformity and a diameter of 30-150 μm are successfully fabricated by a one-step hydrothermal homogeneous precipitation method. To our knowledge, the synthesis of such HA microspheres by using HMT has not been reported yet. Results show that the initial pH value plays a key role in regulating the morphology of the final products and the optimal initial pH value to obtain well-rounded HA microspheres with a porous structure is 3.0-4.0, especially around 4.0. The obtained HA microspheres can be utilized as effective drug carriers for biomedical field.

Crystal structure and formation mechanism of spherical porous hydroxyapatite synthesised in simulated body fluid

ABSTRACTWe synthesized spherical porous hydroxyapatite by a wet method using simulated body fluid and studied its structure. A simulated body fluid with a Ca/P molar ratio of 0.09 was prepared using Dulbecco’s PBS, and spherical porous particles with an average particle size of 13 μm were precipitated therein. All spherical particles were covered with submicron plate-like crystals on the surface. Cross-sectional images showed that pores of submicron to 2 μm in size were present at the centre of the spherical particles. In addition, the plate crystals present on the surface were identified as hydroxyapatite (HAp) with the (002) HAp surface in the longitudinal direction and (100) HAp surface in the width direction, extending in the c-axis direction. Here, we discuss the formation mechanism of the spherical porous HAp.

Preparation of spherical porous hydroxyapatite granules as support materials for microorganisms

Preparation of spherical porous hydroxyapatite granules as support materials for microorganisms

Synthesis spherical porous hydroxyapatite/graphene oxide composites by ultrasonic-assisted method for biomedical applications

Spherical porous hydroxyapatite (SHA)/graphene oxide (GO) composites with different GO (w/w) content of 16%, 40%, and 71% have been fabricated through a facile and controllable ultrasonic-assisted method at room temperature. The products were characterized by x-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, mechanical testing and biomimetic mineralization. Results showed SHA were covered by GO, and SHA/GO composites had an irregular surface with different degrees of wrinkles. The elastic modulus and hardness of SHA/GO-3 composites were up to 12.45 ± 0.33 GPa and 686.67 ± 26.95 MPa, which indicated that the contents of GO had an effect on SHA/GO composites. And the mechanical properties of SHA/GO-2 composites were similar to SHA particles. The biomimetic mineralization in SBF solution showed the bone-like apatite layer on composites surface, which demonstrated that the SHA/GO materials had osseointegration property. Moreover, in vitro cytocompatibility of SHA/GO-2 composites and pure GO were evaluated by cell adhesion and proliferation tests using MC3T3-E1 cells, which demonstrated that the SHA/GO composites can act as a good template for the cells growth and adhesion. These results suggested that the SHA/GO composites will be a promising material for biomedical application.

Evaluation of oil adsorption ability and light reflection properties of spherical porous hydroxyapatite

Evaluation of oil adsorption ability and light reflection properties of spherical porous hydroxyapatite

Evaluation of Protein Adsorption Capacity of TiO<sub>2</sub>-Supported Spherical Porous Hydroxyapatite

In this study, a novel titania-supported spherical porous hydroxyapatite (sHAp + TiO2) was prepared by compounding minute, uniquely shaped spherical porous hydroxyapatites (sHAp) with TiO2. Adsorption of the representative protein bovine serum albumin (BSA) was evaluated and simulated body fluid immersion experiments were carried out. Minimal adsorption of BSA to TiO2 was observed, and 33% and 25% adsorption to sHAp + TiO2 and sHAp were observed, respectively. The reduction in BSA concentration observed in the sHAp and sHAp + TiO2 solutions is presumably due to adsorption to HAp. It is highly likely that adsorption of the acidic protein BSA occurred at the sHAp Ca2+ site. In the simulated body fluid immersion experiments, there was greater expression of hydroxyapatite (HAp) on the surface of sHAp than there was on the surface of sHAp + TiO2. In the case of TiO2 alone, no HAp was produced, even after immersion for 3 days. These results suggest a relationship between BSA adsorption and the osteoconductivity of materials.

Synthesis of Titanium Oxide Photocatalyst Supported on Spherical Porous Hydroxyapatite

Synthesis of Titanium Oxide Photocatalyst Supported on Spherical Porous Hydroxyapatite

Particle diameter control of spherical porous hydroxyapatite by simulated body fluid immersion

Particle diameter control of spherical porous hydroxyapatite by simulated body fluid immersion

Gelatinizing technology combined with gas foaming to fabricate porous spherical hydroxyapatite bioceramic granules

This study fabricated porous spherical hydroxyapatite (HA) bioceramic granules via a novel method by combining the ionotropic gelation of sodium alginate with H2O2 gas-foaming. Firstly, HA powder was dispersed in sodium alginate solution; then, the bubbly slurry prepared by H2O2 gas-foaming was dripped into CaCl2 solution to form hydrogel spheres; finally, these hydrogel spheres were washed, dried and sintered to obtain the HA bioceramic granules. SEM images revealed that the obtained HA granules exhibited spherical shape and interconnected porous structure. XRD, FT-IR and ICP-OES tests confirmed the phase composition and the purity of the HA spherical granules. Compared with commercialized HA irregular granules (BAM® P2040), the HA spherical granules had smaller grain size, more micropores, larger specific surface area and stronger protein adsorption ability. Therefore, the porous spherical HA bioceramic granules shows potential to be a good candidate for bone defect filling materials.

Spherical porous hydroxyapatite granules containing composites of magnetic and hydroxyapatite nanoparticles for the hyperthermia treatment of bone tumor.

Spherical porous granules of hydroxyapatite (HA) containing magnetic nanoparticles would be suitable for the hyperthermia treatment of bone tumor, because porous HA granules act as a scaffold for bone regeneration, and magnetic nanoparticles generate sufficient heat to kill tumor cells under an alternating magnetic field. Although magnetic nanoparticles are promising heat generators, their small size makes them difficult to support in porous HA ceramics. We prepared micrometer-sized composites of magnetic and HA nanoparticles, and then supported them in porous HA granules composed of rod-like particles. The spherical porous HA granules containing the composites of magnetic and HA nanoparticle were successfully prepared using a hydrothermal process without changing the crystalline phase and heat generation properties of the magnetic nanoparticles. The obtained granules generated sufficient heat for killing tumor cells under an alternating magnetic field (300 Oe at 100 kHz). The obtained granules are expected to be useful for the hyperthermia treatment of bone tumors.

Effects of porous-hydroxyapatite incorporated into glass-ionomer sealants.

The purpose of the present study was to evaluate the mechanical and chemical properties of a novel glass ionomer cement for use as a pit and fissure sealant containing a porous hydroxyapatite, namely, apatite ionomer cement (AIC). Control sealant samples were used Fuji III (GIC-S). The experiment sealant samples (AIC-S) consisted of porous spherical hydroxyapatite (HApS) particles added at 28 wt% to GIC-S powder. The GIC-S and AIC-S samples were evaluated through mechanical strength measurements, scanning electron microscopy observations, energy dispersive X-ray spectroscopy analysis, fluoride ion release tests, and antibacterial tests. The flexural strength of the AIC-S was significantly higher than that of GIC-S for each period, 1 h, 24 h and 1 year. The fluoride release dose for AIC-S was consistently higher than that for GIC-S. In addition, the antibacterial properties of AIC-S were superior to those of GIC-S. The novel AIC-S may be a more suitable sealant material for pits and fissures with intact and/or infected enamel.

Fabricating Porous Hydroxyapatite Spheres by a Polymer Sol Route for Biomedical Application

Fabricating Porous Hydroxyapatite Spheres by a Polymer Sol Route for Biomedical Application

Characterisation and photocatalytic activity of structure-controlled spherical granules of an anatase/hydroxyapatite composite

Materials that can purify the environments are desirable. Anatase (TiO 2) has received attention because it is stable and can decompose organic substances because of its photocatalytic activity. To make use of anatase effectively, we deposited nano-sized anatase particles on porous hydroxyapatite (HA) ceramics composed of rod-shaped particles. Spherical porous HA granules composed of rod-shaped HA particles were prepared using a hydrothermal process. The granules were soaked in a solution containing a water-soluble titanium complex and then hydrothermally treated. Nano-sized anatase particles were deposited on each rod-shaped HA particle. The anatase/HA granules composed of rod-shaped HA particles showed higher photocatalytic activity than those composed of globular HA particles. The granules are expected to be useful as an environment-purifying material with high manageability and photocatalytic activity.

Synthesis and release of trace elements from hollow and porous hydroxyapatite spheres

It is known that organic species regulate fabrication of hierarchical biological forms viasolution methods. However, in this study, we observed that the presence of inorganic ionsplays an important role in the formation and regulation of biological sphericalhydroxyapatite formation. We present a mineralization method to prepare ion-dopedhydroxyapatite spheres with a hierarchical structure that is free of organic surfactants andbiological additives. Porous and hollow strontium-doped hydroxyapatite spheres weresynthesized via controlling the concentration of strontium ions in a calcium and phosphatebuffer solution. Similarly, fluoride and silicon-doped hydroxyapatite spheres weresynthesized. While spherical particle formation was attainable at low and high temperaturefor Sr-doped hydroxyapatite, it was only possible at high temperature in theF/Si-doped system. The presence of inorganic ions not only plays an importantrole in the formation and regulation of biological spherical hydroxyapatite, butalso could introduce pharmaceutical effects as a result of trace element release.Such ion release results showed a sustained release with pH responsive behavior,and significantly influenced the hydroxyapatite re-precipitation. These ion-dopedhydroxyapatite spheres with hollow and porous structure could have promising applicationsas bone/tooth materials, drug delivery systems, and chromatography supports.

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.

Drug release from porous hydroxyapatite spheres as a synthetic bone-graft material

Drug release from porous hydroxyapatite spheres as a synthetic bone-graft material

Drug-loaded porous spherical hydroxyapatite granules for bone regeneration

Porous spherical hydroxyapatite (HAp) granules, which are not only can be used for bone void filler, but also drug delivery systems, were prepared using a liquid nitrogen method. Various pore and channel structures of spherical granules were obtained by adjusting the ratio of water to HAp powder and the amount of sodium chloride (NaCl). By using the water to powder ratio at 2.0ml/g and the amount of NaCl at 15wt% by powder, the spherical granules have optimal pore volume, micro-channel structure and strength to handle as well as the ability to work as a drug delivery system. When the NaCl content was 15wt%, the micro-channel structure was changed, but the pore volume was maintained. For the drug release test, dexamathasone (Dex) was loaded as a model drug on the prepared HAp granules by the immersion method, and the drug release behavior was curved by a UV/vis spectrophotometer. As a result, different drug release behavior was observed according to micro-channel structural differences. Therefore, it was concluded that the NACl could be applied as the pore and micro-channel structure control agent. Porous spherical HAp granules, which were fabricated by a liquid nitrogen method, show potential as bone void filler with the ability of controlled drug release.

PREPARATION OF POROUS SPHERICAL HYDROXYAPATITE AGGLOMERATES INTERACTED WITH CYCLODEXTRIN

Porous spherical hydroxyapatite (Ca10(PO4)6(OH)2: HAp) agglomerates with diameters of approximately 1 µm were prepared by: (i) the spray-pyrolysis of calcium phosphate solution containing 0.5 mol dm-3 Ca(NO3)2, 0.3 mol dm-3 (NH4)2HPO4, 0.1 - 0.4 mol dm-3 glutaric acid and concentrated HNO3 at 600°C, using an ultrasonic vibrator, and then (ii) the burnout of residual carbon resulting from the pyrolysis of glutaric acid upon the heat treatment of the spray–pyrolyzed powder at 900°C for 10 min. Three types of resulting HAp powders were then hydrothermally treated with 1.5 mass% β-cyclodextrin (β-CyD) solution at 120°C for 1 h. The amounts of β-CyD in the resulting HAp agglomerates were found to be in the range of 1.1 to 13.1 mass%. Transmission electron microscopy confirmed the presence of β-CyD not only on the surfaces but also inside the spherical HAp agglomerates. When the HAp powder with 13.1 mass% β-CyD addition was immersed in pure water at 90°C for 1 h, the released amount of β-CyD was as low as 2.1 mass%, indicating the enhanced chemical bonding between β-CyD and HAp, due to the hydrothermal treatment.

Preparation of novel hemostatic material containing spherical porous hydroxyapatite/alginate granules

A novel and biocompatible hemostatic material was prepared by mixing porous spherical hydroxyapatite (Ca10(PO4)6(OH)2; HAp)/alginate (AG) granules with a random copolymer of ethylene oxide and propylene oxide (EPO). Two kinds of HAp powders with different particle shapes, i.e., whisker-like HAp (w-HAp; mean long-axis length, 38.0 µm; short-axis length, 1.90 µm) and nanometer-sized HAp (n-HAp; approximate sizes, 0.03 µm × 0.05 µm) were used for the preparation of granules. The HAp–AG granules with diameters of 1.5 to 3.0 mm were prepared through (i) introduction of the spherical droplets containing 2 mass% sodium alginate and HAp particles (w-HAp or n-HAp; HAp/AG = 1.0) into 1 mol·dm−3 CaCl2 solution by using a syringe, (ii) freezing of resulting spherical gels at −80°C and (iii) drying of gels at −50°C for 24 h. The water absorptions of w-HAp/AG and n-HAp/AG granules after 3 d immersion at 37.0°C were 217 mass% and 66 mass%, respectively, indicating that the porosities of the former granules were higher than those of the latter. The stanching times of blood, which were evaluated by measuring how soon the papers on the EPO gels with 60 mass% HAp (i.e., w-HAp and n-HAp)/AG granules got wet by the simulated blood that came out on top of the porous HAp cube (porosity, 70%; mean pore size, 200 µm) due to the capillary force, were estimated to be approximately 5 h.

Preparation of submicrometer-sized porous spherical hydroxyapatite agglomerates by ultrasonic spray pyrolysis technique

Microstructural changes during the heating of submicrometer-sized spherical hydroxyapatite (Ca10(PO4)6(OH)2: HAp) agglomerates were examined. The starting powder was prepared by the spray pyrolysi so f calcium phosphate (Ca/P ratio = 1.67) solution containing 0.0167­1.5mol·dm ¹3 Ca(NO3)2, 0.0100­0.9mol·dm ¹3 (NH4)2HPO4 and concentrated HNO3 at 600°C using an ultrasoni cv ibrator. The resulting powders were composed of spherical agglomerates; the agglomerate diameter was reduced with decreasing concentration of spraying solution. The mean diameter of agglomerates obtained by the spray pyrolysi so f solution with the lowest concentrations, i.e., 0.0167mol·dm ¹3 Ca(NO3)2 and 0.0100mol·dm ¹3 (NH4)2HPO4 (abbreviated as 0.0167/0.0100), was as small as 0.34µm. The spherical agglomerates became hollow following a heat treatment at 800°C for 10min. The incorporation of 0.015mol·dm ¹3 citri ca cid into 0.0167/0.0100 solution contributed to the formation of hollow spherical agglomerates following spray pyrolysis. Furthermore, the heat treatment of these agglomerates at 800°C for 10min increased the amount of pores with mean diameter of 0.2µm, due to the burn-out of residual carbon.