Nano-sized Hydroxyapatite Powders Research Articles

Highly bioactive hydroxyapatite coating made by flame spray technique

This research involves fabrication and characterization of flame sprayed hydroxyapatite (HA) coatings on 316 stainless steel substrates where the desirable structure with high porosity can be obtained. Nano-sized HA powder was synthesized and calcined at 600 °C. The subsequent powder was used as feedstock powder for flame spray technique (FS). In-flight particles of HA were spherical with the range of particle size between 3–37 µm. The average coating thickness was 128 µm and the crystalline phases were a mixture of HA and tricalcium phosphate (TCP). Simulated body fluid (SBF) test showed that HA layer was formed after 7 days. Highly bioactive properties were due to high surface area from rough coating and porous structure, which would be beneficial from the flame spray technique. The coating is promising for applications in biomedical field.

Nano-Hydroxyapatite Isolation and Characterisation of Echinometra mathaei from the Persian Gulf.

The study focuses on the preparation and characterisation (physicochemical and mechanical) of hydroxyapatite [Ca10(PO4)6(OH)2] (HA) from sea urchin, Echinometra mathaei. Therefore, nano-sized HA prepared from sea urchin shells were collected from beaches of the Persian Gulf in Iran. Sea urchin shells were found a source of calcium carbonate in the form of aragonite (calcite) that crystallised in an organic matrix. HA is one of the polymers used in coating the nanoparticles extracted from various sources. The calcined aragonite converted to nanosized hydroxyapatite powder by chemical reaction with orthophosphoric acid while maintaining stoichiometry, Ca/P = 1.667 at 80°C. To determine the purity of the nano-hydroxyapatite (nHA) numerous analytical procedures were used. Fourier transforms infrared spectroscopy (FTIR) confirmed the presence of the peak of 961 cm-1 is related to the symmetric tensile band of the P-O bond, and the peak of 1038 cm-1 and 1091 cm-1 is related to the tensile solid absorption of the PO4 as functional groups of nHA. The nanocrystalline HA can be observed from the SEM images. Thermogravimetric analysis (TGA-DTA) demonstrates the thermal stability of nHA powder. The results show successful isolation and characterisation study of this crucial nano-material shows it is valuable in biomedical applications, particularly in bone tissue engineering. Indeed, its fabrication is easy and economical.

Calcined hydroxyapatite powders with increased chemical stabilities and dispersibility

Biocompatible hydroxyapatite (HAp) powders have thermodynamically driven tendencies to lower their surface areas due to the formation of irreversible aggregates. To address this challenge, HAp hybrid powders are herein prepared by using a traditional wet-precipitation method with subsequent hydrothermal carbonization for surface modification. The crystallite size, crystallite degree and area ratio of the infrared peak assigned to bonding water against those of free water are determined to investigate the variation of HAp crystallization with processing parameters. The crystallization of HAp is facilitated by enriched water in a stealth layer with water molecules evolved by citrate, nitrogen (N)-containing methylene blue (MB), hydrogen-group-rich β-cyclodextrin (CD) and oxygen-containing organic carbon shells. The low surface areas result in fabrication of nano-sized HAp powders with a uniform size distribution, well-dispersed morphologies and smooth surfaces through calcination of HAp-CD-MB@C. The pH values of acidic buffers increase slowly during incubation of HAp-CD-MB@C powders with chemical stability and a large grain size after calcination at 550°C for 2 h. The present study will shed light on the preparation of nano-sized inorganic powders with a uniform size distribution, well-dispersed morphologies and modulated chemical stability for potential applications as carriers of small molecular substances and fillers in composite materials.

Hydroxyapatite Scaffold Manufacturing under the Space Holder Method: Analysis of Physical Properties and Biocompatibility

The space holder method was applied to the manufacture of hydroxyapatite (HA) scaffolds by a pressureless sintering process. The aim is to develop the stages of making scaffold using the space holder method and to prove the readiness of the scaffold, especially from its physical properties and biocompatibility. The novelty of this work is the stages of processing scaffold materials in the form of slurries to produce green body scaffolds. Micron- and nano-sized HA powders were mixed in the form of slurry with polyvinyl alcohol (PVA) and ethanol. The PVA-containing HA was added with polymethyl methacrylate (PMMA) to have ratios ranging from 90:10 wt% to 65:35 wt%. The green bodies were prepared by uniaxial pressing at 200 MPa. The sintering was carried out by preheating at temperature of 700°C with a holding time of 1 h. The temperature was then increased to 1200°C with holding time of 3 h (heating rates were maintained at 5°C/min). The HA scaffolds were characterized by observing the phase, microstructures, and macrostructures; measuring the pores, testing their porosity and compressive strength. The biocompatibility properties were analyzed by testing for direct toxicity. The results indicated that the HA scaffolds made in this study met the standards since the compressive strength value was 2.23 MPa with 65.64% porosity and 126 μm to 385 μm pores size. SEM image showed the interconnection between the pores, the HA scaffolds made were non-toxic. The resulting scaffold has a great potential for further testing in living organisms.

Synthesis and characterization of Fe and Eu containing hydroxyapataite

Hydroxyapatite is the major inorganic component of hard tissues such as bone and dentin. More interestingly, the hydroxyapatites with magnetic properties can be useful for hyperthermia treatment of cancer cells or other tumours. Luminescent properties helps in guiding the magnetic particles in hyperthermia treatment. Magnetic and luminescent properties propelled towards the usage of hydroxyapatites as contrast agents in the bone implants during the magnetic resonance imaging. In the current study, synthesis of magnetic and luminescent nanosized hydroxyapatite powders co-doped with Fe and Eu by microwave synthesis technique was reported. The synthesized nanopowders were annealed at 1000 ˚C for 2 h. Phase compositional studies and functional group analysis of the fabricated nanopowders were carried out by XRD and FTIR. XRD results revealed that co-doping of Fe and Eu resulted in the reduction of crystallite size from 22 nm to 15 nm along with the formation of magnetic Fe3O4 phase in the annealed Fe-EuHA sample. The formation of magnetite phase was confirmed by the ferromagnetic behaviour in the VSM results. PL spectroscopy results revealed that the annealed Fe-EuHA sample exhibited luminescent property in the visible light region.

The Effect of Additive Substitute of MgO Nanoparticle on the Characteristics of Exports as Bone Filler

Research has been conducted on the effect of adding MgO nanoparticle additives to the characteristics of porous hydroxyapatite as bone filler. The purpose of this study was to optimize previous research by replacing the ZnO nanoparticle additive with MgO nanoparticles accompanied by the use of the injection method. Porous hydroxyapatite synthesis is carried out by mixing nano-sized hydroxyapatite powder with MgO nanoparticles and making PVA solution. The composition of MgO nanoparticles varied at 8 wt%, 10 wt%, 12 wt% and 14 wt%. The hydroxyapatite-MgO mixture is dissolved in PVA solution so that the hydroxyapatite slurry is formed. Polyurethane foam is prepared with dimensions of 1 cm × 1 cm × 1 cm. Hydroxyapatite slurry is injected into polyurethane foam and followed by thermal treatments. The thermal treatments process was carried out in 3 stages, the drying stage at 80ºC for 2 hours, the phase of removal of PVA and polyurethane foam by heating in a temperature of 650ºC for 1 hour, and the sintering stage at 1200ºC for 3 hours. The effect of variations in the addition of MgO nanoparticles additives to the porous hydroxyapatite produced was characterized using porosity test, compressive strength test, morphological test with SEM, functional group test with FTIR, and cytotoxicity test using MTT assay. Based on the analyzes that have been done, it is known that the porous hydroxyapatite sample with the addition of 14 wt% of the MgO nanoparticle additive shows the best character with a porosity percentage of 68.60%, compressive strength value of 2.43 MPa, pore size of 100.3 - 314.3 µm, and not toxic.

Effect of Solution and Calcination Time on Sol-gel Synthesis of Hydroxyapatite

Nano-sized hydroxyapatite (HA) particles were synthesized by sol-gel through water and ethanol based mediums of phosphoric acid (H3PO4) and calcium hydroxide (Ca(OH)2) at pH = 11 for different calcination time (1 h, 2 h, 4 h). The effects of calcination time and solution on the crystallinity, morphology and impurity phases of the HA nanoparticles were examined via Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). It was found that crystallite size and the fraction crystallinity of the synthesized samples increased with calcination time. According to solution medium, only CaO as impurity was appeared in the water-based solvent, CaO and Ca(OH)2 impurities were appeared in the ethanol-based solvent. The lowest crystallinity was 0.92 and the highest crystallinity was 1.73 respectively, depending on the process parameters. The Ca/P atomic ratio closest to the bone was found as 1.5178. As a result, the employed water-based sol-gel processes for 1 h calcination time was determined as the optimum for the formation of nano-sized HA powders using calcium hydroxide and phosphoric acid.

Characterization of hydroxyapatite derived from eggshells for medical implants

Abstract Nano-sized Hydroxyapatite (HAp) powders are synthesized from natural bio-waste chicken eggshell. The synthesized powder is characterized using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) which confirms the formation of HAp. Scanning Electron Microscopy (SEM) shows highly porous agglomerated HAp powder with average pore diameter of 276.3 nm. EDAX analysis reveals calcium and phosphate ratio (Ca/P) of 1.74 showing close resemblance to human bone. Transmission electron microscopy (TEM) reveals formation of spherical shaped HAp powder with average particle size of 78 nm. The synthesized nano HAp powder is suitable for coating on medical implants.

Characterization of Hydroxyapatite Coating on Ti6Al4V by Sol-gel Method

Biomaterials are natural or synthetic materials that are used in human body and are materials to evaluate, treat, support or replace any tissue, organ, or function of the body. Due to its favorable biocompatibility and mechanical properties, HA-coated metal-based implants are used in the orthopedic surgery operations. For this purpose, sol-gel synthesized nano sized HA powders were produced. Ti6Al4V alloy was coated with hydroxyapatite(HA) by using the sol–gel method. Surface morphologies, thermal, mineralogical properties and bioactivity of the coatings were examined and the characterization of the coatings was performed by using DTA-TG, XRD, SEM, and EDX.

Low Temperature Development of Nano-Hydroxyapatite from Austromegabalanus psittacus, Star fish and Sea urchin

The study focuses the preparation and characterization (physico-chemical and mechanical) of hydroxyapatite [Ca10(PO4)6(OH)2] (HAp) from naturally occurring dead marine species widely available in Arabian sea shore; namely Austromegabalanus psittacus, star fish (Asteroidea) and sea urchin (Echinoidea). All three marine species were found to be source of calcium carbonate in the form of aragonite (calcite) that crystallize in an organic matrix. The calcined aragonite was converted to nano-sized hydroxyapatite powder by chemical reaction with Ortho-phosphoric acid while maintaining stoichiometry, Ca/P = 1.67 at 80 °C. It was found from XRD that the powders were composed of pure HAp with average crystallite size of 10 nm. SEM, on the other hand, revealed nano-rod like elongated structures having a length in the range of 100 to 700 nm with an aspect ratio of 3.5. Further, the HAp powders were used to prepare cylindrical pellet samples by uni-axial pressing, sintered at 1100 °C temperature, made flat-parallel, polished and used finally for assessment of elastic modulus by compression test method. Primary results showed typical elastic modulus of pellets from Austromegabalanus psittacus is 3 GPa, star fish 2.1 GPa and sea urchin 2.3 GPa (L/D = 1.3 and strain rate = 0.01 mm/s). Thus, the powder synthesized from marine source could be a potential alternative for development of structural bio-ceramics and also can be used as scaffolds for bone or dental implants, because of its easy and economical fabrication.

Different Synthesis Routes for Hydroxyapatite Nanoparticles by Mechanical Stirring

Nanosized hydroxyapatite (HA) with crystallinity and composition similar to bone apatite has been widely investigated in the last years, due to their excellent biocompatibility in bone replacement applications. This bioceramic can be synthesized by many wet chemical and mechanochemical methods. In this paper, nanosized hydroxyapatite powders were synthesized by two wet chemical routes using mechanical stirring method. The first route was used for HA synthesis from CaCl2.2H2O and Na3PO4.12H2O solutions and the second route was from Ca (OH)2 and H3PO4 solutions. The synthesized HA nanoparticles were characterized by Dynamic Light Scattering, BET Surface Area analysis, X-ray Diffraction, Infrared Spectroscopy, chemical analysis and Scanning Electron Microscopy. The results indicated that HA nanoparticles were successfully synthesized by both wet chemical precipitation routes and all powders presented a Ca/P ratio similar to stoichiometric HA, nanoneedles morphology and single HA crystalline phase.

NGHIÊN CỨU TỔNG HỢP VÀ ĐẶC TRƯNG HÓA LÍ CỦA BỘT NANO BARI HYDROXYAPATIT

NGHIÊN CỨU TỔNG HỢP VÀ ĐẶC TRƯNG HÓA LÍ CỦA BỘT NANO BARI HYDROXYAPATIT

Laser Annealing for Gas-Dynamical Spraying of HA Coating upon a Titanium Surface

Laser post-heating computer controlled detonation spraying (CCDS) and cold spray (CS) hybrid processes were proposed for fabrication of near sub micron structure coatings of hydroxyapatite (HA) + Ti system. Optical and SEM with energy dispersive X-ray analysis and comparative XRD phase analysis were used to evaluate microstructure. After those hybrid processes, no substantial variation in HA composition was noted by structural and phase examination. Nano-sized HA powders can be recommended for laser annealing CS (LaCS) process. Regimes of laser treatment optimal for increasing the adhesion between the HA and titanium coatings, providing more strength, ductility and decreasing of HA destruction in the coatings were determined.

Preparation and characterization of nano-sized hydroxyapatite/alginate/chitosan composite scaffolds for bone tissue engineering.

The aim of this study was to develop chitosan composite scaffolds with high strength and controlled pore structures by homogenously dispersed nano-sized hydroxyapatite (nano-HAp) powders. In the fabrication of composite scaffolds, nano-HAp powders distributed in an alginate (AG) solution with a pH higher than 10 were mixed with a chitosan (CS) solution and then freeze dried. While the HAp content increased up to 70 wt.%, the compressive strength and the elastic modulus of the composite scaffolds significantly increased from 0.27 MPa and 4.42 MPa to 0.68 MPa and 13.35 MPa, respectively. Higher content of the HAp also helped develop more differentiation and mineralization of the MC3T3-E1 cells on the composite scaffolds. The uniform pore structure and the excellent mechanical properties of the HAp/CS composite scaffolds likely resulted from the use of the AG solution at pH 10 as a dispersant for the nano-HAp powders.

Blind micro-hole array Ti6Al4V templates for carrying biomaterials fabricated by fiber laser drilling

Blind micro-hole array templates were constructed by laser drilling using a 20W fiber laser on a Ti6Al4V substrate to improve carrying capacity of Ti6Al4V substrate to biomaterials in this study. The influence of laser parameters on the morphology of the blind holes was investigated and the blind micro-hole array templates were fabricated by the optimized laser parameters. Three typical morphologies were generated through adjusting laser parameters. The type II micro-hole characterized by column-shaped entrance and a hemispherical dome bottom is believed to have a suitable morphology, which was produced by the optimized laser parameters, i.e., defocusing distance 0mm, laser average power 16W, laser irradiation time 1ms and repetition rate 25kHz. The blind micro-hole templates with different micro-hole density were constructed by the mentioned-above optimized parameters and then the nano-sized hydroxyapatite (HA) powders were uniformly deposited into the blind micro-hole templates by electrophoretic deposition. Finally, the dynamic behavior of laser-drilling process was analyzed.

Effect of Iron on the Sinterability and Properties of HA/Ti-Fe Composites

Dense iron-containing hydroxyapatite (HA)/titanium composites were synthesized via pressureless sintering at a relatively low temperature using nanosized HA powders and Ti-Fe mixed powders. XRD analysis showed that desirable Ti phase still remained in the HA matrix. The addition of iron improved the densification by enhancing the sinterability of titanium, and reduced the decomposition rate of HA and the interaction between HA and titanium. The mechanical tests showed that both the flexural strength and fracture toughness of the composites were significantly improved. The Ti-Fe reinforcing particles exhibited plastic stretching and bridged an advancing crack, making a significant contribution to the improvement of mechanical properties of the composites.

In vitro and in vivo bioactivity assessment of a polylactic acid/hydroxyapatite composite for bone regeneration

Synthetic bone graft substitutes based on composites consisting of a polymer and a calcium-phosphate (CaP) ceramic are developed with the aim to satisfy both mechanical and bioactivity requirements for successful bone regeneration. In the present study, we have employed extrusion to produce a composite consisting of 50 wt.% poly(D,L-lactic acid) (PLA) and 50 wt.% nano-sized hydroxyapatite (HA) powder, achieving homogeneous distribution of the ceramic within the polymeric phase. In vitro, in both a simulated physiological saline (SPS) and a simulated body fluid (SBF), a greater weight loss was observed for PLA/HA than for PLA particles upon 12-week immersion. Furthermore, in SPS, a continuous release of calcium and phosphate from the composite was measured, whereas in SBF, decrease of the amount of the two ions in the solution was observed both for PLA and PLA/HA accompanied with the formation of a CaP layer on the surface. In vitro characterization of the composite bioactivity was performed by culturing human mesenchymal stromal cells (hMSCs) and assessing proliferation and osteogenic differentiation, with PLA as a control. Both PLA/HA composite and PLA control were shown to support hMSCs proliferation over a period of two weeks. In addition, the composite significantly enhanced alkaline phosphatase (ALP) activity of hMSCs in osteogenic medium as compared with the polymer control. A novel implant design was employed to develop implants from dense, extruded materials, suitable for testing osteoinductivity in vivo. In a preliminary study in dogs, PLA/HA composite implants induced heterotopic bone formation upon 12-week intramuscular implantation in all animals, in contrast to PLA control, which was not osteoinductive. Unlike in vitro, a more pronounced degradation of PLA was observed in vivo as compared with PLA/HA composite.

Hydroxyapatite가 도핑된 Ti-6Al-4V 구형 분말의 전기방전 소결 및 소결체 특성에 관한 연구

Spherical Ti-6Al-4V powders in the size range of 250 and 300 were uniformly doped with nano-sized hydroxyapatite (HAp) powders by Spex milling process. A single pulse of 0.75-2.0 kJ/0.7 g of the Ti-6Al-4V powders doped with HAp from 300 mF capacitor was applied to produce fully porous and porous-surfaced Ti-6Al-4V implant compact by electro-discharge-sintering (EDS). The solid core was automatically formed in the center of the compact after discharge and porous layer consisted of particles connected in three dimensions by necks. The solid core increased with an increase in input energy. The compressive yield strength was in a range of 41 to 215 MPa and significantly depended on input energy. X-ray photoelectron spectroscopy and energy dispersive x-ray spectrometer were used to investigate the surface characteristics of the Ti-6Al-4V compact. Ti and O were the main constituents, with smaller amount of Ca and P. It was thus concluded that the porous-surfaced Ti-6Al-4V implant compacts doped with HAp can be efficiently produced by manipulating the milling and electro-discharge-sintering processes.

Strength and fatigue properties of three-step sintered dense nanocrystal hydroxyapatite bioceramics

Dense hydroxyapatite (HA) ceramic is a promising material for hard tissue repair due to its unique physical properties and biologic properties. However, the brittleness and low compressive strength of traditional HA ceramics limited their applications, because previous sintering methods produced HA ceramics with crystal sizes greater than nanometer range. In this study, nano-sized HA powder was employed to fabricate dense nanocrystal HA ceramic by high pressure molding, and followed by a three-step sintering process. The phase composition, microstructure, crystal dimension and crystal shape of the sintered ceramic were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties of the HA ceramic were tested, and cytocompatibility was evaluated. The phase of the sintered ceramic was pure HA, and the crystal size was about 200 nm. The compressive strength and elastic modulus of the HA ceramic were comparable to human cortical bone, especially the good fatigue strength overcame brittleness of traditional sintered HA ceramics. Cell attachment experiment also demonstrated that the ceramics had a good cytocompatibility.

Formation mechanism of nano-sized hydroxyapatite powders through spray pyrolysis of a calcium phosphate solution containing polyethylene glycol

Abstract Nano-sized hydroxyapatite powders were synthesized by spray pyrolysis of a calcium phosphate solution containing polyethylene glycol (PEG) and a subsequent dewaxing process. Calcium phosphate solutions (Ca/P ratio of 1.67) were prepared by dissolving calcium nitrate tetrahydrate and diammonium hydrogen phosphate in deionized water with and without PEG and subsequently adding nitric acid. When the calcium phosphate solution was sprayed at 1100 °C at a carrier gas flow rate of 40 L/min, micron-sized hollow hydroxyapatite particles with dense or collapsed shells were obtained. However, when the calcium phosphate solution containing PEG was sprayed under the same conditions, micron-sized porous hydroxyapatite particles consisting of loosely packed hydroxyapatite crystals containing randomly placed carbons were obtained. When these hydroxyapatite particles were dewaxed at 650 °C for 3 h, they were completely disintegrated into nano-sized hydroxyapatite particles, whereas the micron-sized hollow hydroxyapatite particles without carbons remained intact. After sintering at 1100 °C for 3 h, the relative densities of hydroxyapatite disks made from micron- and nano-sized powders were 78.5 ± 1.7% and 99.8 ± 0.3%, respectively. The practical implication of these results is that highly sinterable nano-sized hydroxyapatite powders can be synthesized through spray pyrolysis of a calcium phosphate solution containing PEG.