Hydroxyapatite Particle Size Research Articles

Rapid synthesis and characterization of silicon substituted nano hydroxyapatite using microwave irradiation

Nano sized hydroxyapatites with silicon substitution of three different silicon concentrations were successfully prepared first time by a rapid microwave assisted synthesis method, with a time saving and energy efficient technique. The effects of the Si substitution on crystallite size, particle size and morphology of the powders were investigated. The crystalline phase, microstructure, chemical composition, and morphology and particle size of hydroxyapatite and silicon substituted hydroxyapatites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and dynamic light scattering. The crystallite size and particle size decreases with increase in silicon content and particle morphology spheroidal for pure hydroxyapatite changes to elongated ellipsoidal crystals while silicon substitution increases. Fourier Transform Infrared Spectroscopy analysis reveals, the silicon incorporation to hydroxyapatite lattice occurs via substitution of silicate groups for phosphate groups. Substitution of phosphate group by silicate in the apatite structure results in a small increase in the lattice parameters in both a-axis and c-axis of the unit cell.

Effect of calcining temperature on particle size of hydroxyapatite synthesized by solid-state reaction at room temperature

Using diammonium phosphate, calcium nitrate tetrahydrate and sodium bicarbonate as raw materials, hydroxyapatite (HAP) was facilely synthesized by solid-state reaction at room temperature. The crystallinity, phase, morphology and particle size of the products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry/differential thermal analysis (TG–DTA) and particle size analyzer. The influence of calcining temperature on the crystallinity and composition of HAP phase was also investigated.

Hydroxyapatite nanoparticles: Electrospinning and calcination of hydroxyapatite/polyvinyl butyral nanofibers and growth kinetics

Electrospinning of hydroxyapatite (HA)/polyvinyl butyral solution resulted in the formation of fibers with average diameter of 937-1440 nm. These fibers were converted into HA nanoparticles with size <100 nm after undergoing calcination treatment at 600°C. The diameter of the fiber was found to be influenced by applied voltage and spinning distance. The injection flowrate did not affect the diameter significantly. The electrospinning method successfully reduced the commercial HA particle size in the range of 400-1100 nm into <100 nm. The dispersion of the finally calcined HA nanoparticles was improved significantly after anionic sodium dodecyl sulfate surfactant was introduced. The experimental data of HA growth kinetics were subjected to the integral method of analysis, and the rate law of the reaction was found to follow the first order reaction.

The Size Control of Hydroxyapatite Particles during Spray Pyrolysis

The size of hydroxyapatite particles during spray pyrolysis was successfully controlled by varying the concentrations of the starting calcium phosphate (CaP) solutions. Three different concentrations of CaP solutions were prepared by dissolving Ca (NO3)2·4H2O and (NH4)2HPO4 into deionized water and then they were sprayed at 900°C with the carrier gas flowing rate of 10 L/min. The size of the resultant hydroxyapatite particles decreased as lowering the concentration of the starting CaP solution. The smaller the particle size, the higher the relative density of the hydroxyapatite disks after sintering at 1100°C for 1 hour. The practical implication of the results is that highly sinterable hydroxyapatite particles can be synthesized during spray pyrolysis by controlling the starting concentration of CaP solution.

Tailoring gel modulus using dispersed nanocrystalline hydroxyapatite

Mammalian cells are known to respond to the elastic modulus of the surface to which they adhere. Consequently, there is interest in developing strategies to control the elastic moduli of materials, including hydrogels. One way of controlling modulus in hydrogels is to introduce reinforcing agents such as inorganic materials, for example hydroxyapatite (HA). Although several authors have reported the reinforcement of hydrogels with ceramic particles, there have not been any studies to investigate the effect of size and crystallinity of HA particles on the mechanical properties of hydrogel. In this study, synthetic Calcium phosphate of two different crystallite sizes: one on the nano-scale (∼50 nm) and the other on the micro-scale (∼150 nm) have been used to manufacture HA/gellan gum (GG) composites. It was shown that while nano-scale HA (nHA) reinforced the hydrogel structure, the micro-scale HA (mHA) material acted to weaken it (2.5 wt% HA). Furthermore, it was found that by increasing the content of the nHA in the composite to 50 wt%, the yield strength and bulk modulus was increased by four- and nine-fold, respectively. The reinforcing effect of nHA was attributed to its higher association with the GG coil structure when compared with the mHA, which disrupted gel structure.

Rapid hydrothermal flow synthesis and characterisation of carbonate- and silicate-substituted calcium phosphates

A range of crystalline and nano-sized carbonate- and silicate-substituted hydroxyapatite has been successfully produced by using continuous hydrothermal flow synthesis technology. Ion-substituted calcium phosphates are better candidates for bone replacement applications (due to improved bioactivity) as compared to phase-pure hydroxyapatite. Urea was used as a carbonate source for synthesising phase pure carbonated hydroxyapatite (CO3-HA) with ≈5 wt% substituted carbonate content (sample 7.5CO3-HA) and it was found that a further increase in urea concentration in solution resulted in biphasic mixtures of carbonate-substituted hydroxyapatite and calcium carbonate. Transmission electron microscopy images revealed that the particle size of hydroxyapatite decreased with increasing urea concentration. Energy-dispersive X-ray spectroscopy result revealed a calcium deficient apatite with Ca:P molar ratio of 1.45 (±0.04) in sample 7.5CO3-HA. For silicate-substituted hydroxyapatite (SiO4-HA) silicon acetate was used as a silicate ion source. It was observed that a substitution threshold of ∼1.1 wt% exists for synthesis of SiO4-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy.

Synthesis of nanoscale hydroxyapatite particles using triton X-100 as an organic modifier

Nano-sized rod like hydroxyapatite (HA) particles were synthesized using Ca(NO3)2·4H2O and (NH4)2HPO4 as precursors with varying contents of non-ionic surfactant viz., p-(1,1,3,3-tetramethylbutyl)phenoxypoly(oxyethylene)glycol (triton X-100) as organic modifer. The crystalline phase, chemical composition, surface area and morphology of the prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET surface area analysis, high resolution scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM). The above studies indicate the presence of nanoscale hydroxyapatite (HA) phase. Triton X-100 does not appear to affect the crystallinity of the samples. Increase of BET surface area and the consequent decrease in particle size of HA were observed as a function of surfactant content. Probable mechanism for the role of the surfactant in the synthesis of nanoscale HA has also been discussed.

Synthesis and Characterization of Sol-Gel Derived Hydroxyapatite-Bioglass Composite Nanopowders for Biomedical Applications

The main purpose of this study is to prepare and characterize hydroxyapatite (HA)–10%wt bioglass (BG) composite nanopowders and its bioactivity. Composites of hydroxyapatite with synthesized bioglass are prepared at various temperatures. Suitable calcination temperature is chosen by evaluating of the phase composition. X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) techniques are utilized to characterize the prepared nanopowders. The bioactivity of the prepared composite samples is evaluated in an in vitro study by immersion of samples in simulated body fluid (SBF) for predicted time. Fourier transformed infrared (FTIR) spectroscopy and inductively coupled plasma (ICP) are used for evaluation of apatite formation and the bioactivity properties. Results show that HA-BG composite nanopowders are successfully prepared without any decomposition of hydroxyapatite. The suitable temperature for calcination is 600°C and the particle size of hydroxyapatite is about 40-70 nm. The apatite phase forms after 14 days immersing of the samples in SBF. It could be concluded that this process can be used to synthesize HA-BG composite nanopowders with improved bioactivity which is much needed for hard tissue repair and biomedical applications.

Bone‐nanohydroxyapatite spheres interface evaluation by synchrotron radiation X‐ray microfluorescence

Hydroxyapatite (HA) is largely used as bone graft; it seems to be the most promising synthetic implant material, mainly because of its excellent biocompatibility. The crystallinity, particle and pore size of HA are important characteristics and can be modified by decreasing basic structural form below 100 nm and have evoked a great amount of attention for improving prevention, diagnosis, and disease treatment, besides improving bone repair through the biodegradation of the material. The aim of this study was to investigate bone mineral content in bone samples with nanohydroxyapatite and HA spheres, specially its spatial distribution on bone microarchitecture. Circular bone defects were made in both tibiae of 12 White New Zeland adult rabbits (Oryctolagus cuniculus) and were divided randomly into five groups – blood clot (control group), sintered HA, non‐sintered HA, sintered nanoHA and non‐sintered nanoHA – all materials in spherical shape, to smooth handling and accommodation of the surgical bed, and to minimize inflammatory response. The rabbits were euthanatized according to the experimental period of 1 and 4 weeks after surgery. The samples were evaluated by polarized microscopy as well as X‐ray microfluorescence in order to account the bone mineral content bone‐implant interfaces, through synchrotron radiation. Our results revealed greater newly formed bone area in the non‐sintered materials and control groups, and the used technique showed that the amount of calcium of new bone was consistent with both mature bone and HA spheres. In conclusion, the present findings suggest that HA‐based biomaterials are biocompatible, promote osteoconduction and favored bone repair. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Large scale synthesis of hydroxyapatite nanospheres by high gravity method

Hydroxyapatite (HAp) nanospheres were synthesized in large scale using high gravity method. The effects of flow rates (300, 500 and 700 mL/min) and rotating speeds (1000, 2000 and 3000 rpm) on the size, distribution and morphology of nanoparticles were studied. The liquid flow rate and rotation speed was found to have a great influence on the formation of nanoparticles and uniform size distribution. The particle size decreased with an increase in the rotation speed of the RPB. The particle size was observed to be smaller at a lower liquid flow rate compared to that of the high liquid flow rate. TEM images of the granular HAp nanoparticles clearly displayed the spherical shape of nanoparticles. Densely assembled arranged nanospheres with diameters of 20–40 nm were observed at various rpm values. The obtained nanospheres appeared to be single crystalline from the image and SAED pattern analyses. In vitro cellular analysis showed very good improvement in the cell adhesion. For mechanical analysis, HAp/HMWPE composite was fabricated. The smaller size of HAp particles provided a relatively homogenous mixture of HAp and HMWPE which ensured the good mechanical strength.

Effect of polypropylene molecular weight, hydroxyapatite particle size, and Ringer’s solution on creep and impact behavior of polypropylene-surface treated hydroxyapatite biocomposites

In this study, bovine bone was burnt at 400°C and the resulting ash was heat-treated at 900°C for 90 min to get a white powder. Chemical analysis showed that this white powder was mainly hydroxyapatite (HA). Three different average particle sizes of this powder were produced by milling at three different times. The produced HA was surface treated with a silane coupling agent. Composite samples with 40 vol.% of HA were produced by hot press molding and so mechanical testing was done on the specimens in air and Ringer’s solution. The results of these tests showed that on increasing the molecular weight of polypropylene (PP), creep strain of composites decreases proportionally, and ultimate tensile strength (UTS) and impact resistance increase dramatically. In addition, result of mechanical tests on the soaking specimens in Ringer’s solution showed that Ringer’s solution intensively decreases UTS, creep, and impact properties of PP—HA composite. Furthermore, decreasing HA particle size caused UTS rise, creep strain fall, and impact resistance rise for composites in air condition. Vice versa, in wet condition, decreasing HA particle size caused UTS, creep, and impact resistance to fall. Fracture surfaces of impact samples tests were analyzed by a scanning electron microscope.

Effect of Molecular Weight, Particle Size and Ringer’s Solution on Mechanical Properties of Surface-treated Polypropylene-Hydroxyapatite Biocomposites

Bovine bone is burned at 400°C and the resulting ash is heat treated at 900°C for 90 min in order to obtain a white powder. Chemical analysis shows that this white powder is mainly hydroxyapatite (HA). Three different average particle sizes of this powder are produced by milling at three different times. The produced HA is surface treated with a silane coupling agent. Composite samples with 40% (by volume) of HA are produced by hot press molding, followed by mechanical testing in air and in Ringer’s solution. The results show that by increasing the molecular weight of polypropylene (PP), the creep strain of composites decreases proportionally, and the ultimate tensile strength (UTS) and impact resistance increase dramatically. In addition, the effect of testing in Ringer’s solution is to decrease UTS, creep, and impact properties of PP-HA composites. Furthermore, by decreasing the HA particle size, the creep strain decreases, while the UTS and impact resistance increase for the composites tested in air. Vice versa, in a wet condition decreasing of HA particle size causes UTS, creep, and impact resistance to fall. Fracture surfaces of the samples after impact tests are analyzed by a scanning electron microscope.

Mechanical properties of hydroxyapatite‐filled ethylene vinyl acetate copolymer composites: Effect of particle size and morphology

AbstractPliable and bioactive composites made of hydroxyapatite (HAP) and ethylene vinyl acetate (EVA) copolymer were developed for the repair of defective cranium. This article describes the mechanical properties of HAP–EVA composites. The effects of HAP particle size and morphology of HAP on the properties of resultant composites were investigated using various techniques. It was found that the composites containing smaller HAP particles had higher values of tensile modulus, flexural modulus, and impact strength. Examination of the fracture surfaces revealed that only a mechanical bond existed between the filler and the matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The influence hydroxyapatite nanoparticle shape and size on the properties of biphasic calcium phosphate scaffolds coated with hydroxyapatite–PCL composites

We developed a composite biphasic calcium phosphate (BCP) scaffold by coating a nanocomposite layer, consisting of hydroxyapatite (HA) nanoparticles and polycaprolactone (PCL), over the surface of BCP. The effects of HA particle size and shape in the coating layer on the mechanical and biological properties of the BCP scaffold were examined. Micro-computerized tomography studies showed that the prepared scaffolds were highly porous (∼91%) with large pore size (400–700 μm) and an interconnected porous network of ∼100%. The HA nanoparticle (needle shape)-composite coated scaffolds displayed the highest compressive strength (2.1 ± 0.17 MPa), compared to pure HA/β-TCP (0.1 ± 0.05 MPa) and to the micron HA – composite coated scaffolds (0.29 ± 0.07 MPa). These needle shaped scaffolds also showed enhanced elasticity and similar stress–strain profile to natural bone. Needle shaped coated HA/PCL particles induced the differentiation of primary human bone derived cells, with significant upregulation of osteogenic gene expression (Runx2, collagen type I, osteocalcin and bone sialoprotein) and alkaline phosphatase activity compared to other groups. These properties are essential for enhancing bone ingrowth in load-bearing applications. The developed composite scaffolds possessed superior physical, mechanical, elastic and biological properties rendering them potentially useful for bone tissue regeneration.

Fabrication and characterization of a biomimetic composite scaffold for bone defect repair

For successful bone tissue engineering, scaffolds with tailored properties are a basic requirement. The combination of different available materials not only appears to be desirable but also very challenging. In this study, a composite material consisting of hydroxyapatite and collagen was produced by a biomimetic precipitation method and characterized by X-ray diffraction (XRD) and thermogravimetry (TGA). Subsequently, a suspension-quick-freezing and lyophilization method was used to incorporate the hydroxyapatite into a polymeric matrix consisting of collagen and chitosan. Before physicochemical characterization, the highly porous scaffolds were consolidated by a dehydrothermal treatment (DHT). The main attention was focused on the particle size of hydroxyapatite, which should be in the nanometer range. This is relevant to achieve a homogeneous resorption of the material by osteoclasts. Small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and environmental scanning electron microscopy (ESEM) were used to evaluate the outcome. The results suggest a successful polymeric embedding of nanoscaled hydroxyapatite particles into the matrix of the spongy construct. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Rat Mastoid Bullae Obliteration with Hydroxyapatite: Histopathologic Results with Various Size of Hydroxyapatite

Background and ObjectivesZZMastoid obliteration is the technique developed to reduce cavity problems after canal wall down mastoidectomy. Different materials have been explored for the technique, and of the variety of materials that have been used for mastoid obliteration, hydroxyapatite has gained particular attention. Hydroxyapatite can be made into a specific particle size, which affects the postoperative result. The aim of this study is to evaluate the histopathologic findings of mastoids obliterated with various particle sizes of hydroxyapatite in the temporal bullae of rat. Materials and MethodZZRat bullaes were obliterated with hydroxyapatite and diversified into different particle sizes. In group 1, the mastoids were obliterated with Mimix ® powder and in groups 2, 3, 4 with Bongros ® . The particle sizes were 0.3-0.6 mm, 0.6-1.0 mm and 1.0-3.0 mm each. After 3 months, the mastoids were examined under the microscope. ResultsZZIn group 1, a new bone was formed in a consecutive fashion from the mastoid wall toward the center of the mastoid; there was no inflammation, with the new bone formation constituting 15%. In group 2, 3, 4, the proportion of new bone formation was higher than in the group 1, and constituted 40%, 55% and 60%, respectively. Inflammation was more severe when the particle size became larger. ConclusionZZNew bone formation was faster if larger hydroxyapatite particles were used; however, inflammation also increased. The powder form of hydroxyapatite was slow in new bone formation, but there was little inflammation. We therefore think that the hydroxyapatite is a very safe material. Korean J Otorhinolaryngol-Head Neck Surg 2010;53:209-14 Key WordsZZTemporal bone·Mastoid·Osteogenesis·Hydroxyapatites·Particle size.

Hydroxyapatite particles as drug carriers for proteins

Recently, much attention has been paid to hydroxyapatite (HA) particles as protein drug carriers. HA is biological substance like tooth and bone, and HA has biodegradable and biocompatible property. Also HA has high affinity for versatile substances, such as proteins. The aim of this study was to prepare HA particles and to evaluate the effects of various experimental conditions on particles properties (i.e. shape and amount of protein adsorption to HA). HA particles were prepared by three methods including solvent diffusion methods, the method using sintering porous HA microgranules, and homogeneous precipitation method. Complicated spiky crystals were prepared by solvent diffusion method, whereas spherical amorphous agglomerates were prepared by sintering of porous HA granules. Spherical particles were obtained by homogeneous precipitation method and were well dispersed. The spherical particles were composed of minute spiky crystals. The temperature and time duration of the producing process and the amount of additives, such as urea and EDTANa 2, strongly affected the particle shape and size. When the production process is kept under low temperature, tiny crystals were not mutually sintered and also their aggregation was not deposited. Also, inhomogeneous crystal growth occurred when the reaction time was long. Addition of enough amount of EDTANa 2 to reaction solution made the small and spherical HA particles. Bovine serum albumin (BSA) or lysozyme hydrochloride (LSZ)-adsorbed HA particles were prepared. The affinity of HA particles and release profile of proteins from the particles were evaluated. X-ray powder diffraction measurements suggested that the surface area ratio of a plane against total surface area of HA crystal became smaller by decreasing EDTANa 2 concentration. The surface of plane a is positively charged but that of plane c is negatively charged. HA particle size decreased as EDTANa 2 concentration increased. The amounts of BSA and LSZ adsorbing onto HA particle surface were different, since BSA was negatively charged and LSZ was positively charged in the solution. Therefore BSA seems to adsorb onto plane c, whereas LSZ adsorb onto plane a. The differences of the ratio of surface a plane against the total surface area of HA particles and particles size influenced the amount of protein adsorption. The sustained release of BSA and LSZ from HA particles were observed for two weeks.

Synthesis of mesoporous structured hydroxyapatite particles using yeast cells as the template

In this study, hydroxyapatite (HAp) particles with mesoporous structure have been synthesized from calcium hydroxide and di-ammonium hydrogen phosphate using yeast cells as the template. The characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectrograph (FTIR), N(2) adsorption-desorption isotherms (NADI), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were used for determination of the particles structure (particle size, structural evolution and morphology). The results show that HAp particles with mesoporous structure could be produced. The size of HAp particles was approximately hundreds of nanometer. The pore width of HAp particles was in the range of 2.0-40 nm and the maximum centered around 4.5 nm.

γ-Radiation Assisted Fabrication of Hydroxyapatite-Polyacrylamide Nanocomposites with Possible Application in Bone Implantology

Hydroxyapatite (HA) impregnated poly-(acrylamide) nanocomposites were synthesized using γ-radiations and the prepared composites were characterized by different instrumental techniques. Fourier transform infrared spectroscopy studies revealed the presence of carbonated HA, while the X-ray diffraction analysis showed the mean particle size of HA to be nearly 6.53 nm and width 1.278 nm. The nanosize of the hydroxyapatite crystals were also confirmed by Transmission electron microscopy analysis. The crystallinity of material was found to be 76.10% with interchain separation between 0.1998 and 0.1933 nm for native HA and HA nanocomposites, respectively. Thermogravimetric analysis studies resulted in the thermogram that resembled with that of the natural bone. Scanning electron microscope results revealed the pore size of prepared composite ranging between 50 and 100 µm. The modulus and compressive strength of prepared materials were found to be 726.40 and 39.55 MPa, respectively. Water uptake capacity of the prepared nanocomposites was quantified in terms of swelling ratio and the data were used to calculate network parameters of HA-PAm composites. The in vitro - blood compatibility results confirmed a fair level of blood compatibility of the prepared composites.

Cyclic acetal hydroxyapatite composites and endogenous osteogenic gene expression of rat marrow stromal cells

In this study, bone marrow stromal cells (BMSCs) were differentiated on cyclic acetal composites containing hydroxyapatite (HA) particles (110 or 550 nm). These composites were evaluated for their role in influencing osteogenic signalling by encapsulated BMSCs. While a number of factors exert influence on osteogenic signalling during the production of an osteogenic matrix, we hypothesize that HA particles may upregulate bone growth factor expression due to enhanced BMSC adhesion. To this end, fluorescence-activated cell sorting (FACS) analysis was performed for the evaluation of BMSC surface marker expression after culture on two-dimensional (2D) cyclic acetal/HA composites. Three-dimensional (3D) composites were then fabricated by incorporating 110 or 550 nm HA particles at 5, 10 and 50 ng/ml concentrations. Bone growth factor molecules (TGFbeta1, FGF-2 and PDGFa), bone biomarker molecules (ALP, OC, OPN and OCN) and extracellular matrix-related molecules (FN, MMP-13, Dmp1 and aggrecan) were selected for evaluation of osteogenic signalling mechanisms when in presence of these composites. FACS results at day 0 demonstrated that BMSCs were a heterogeneous population with a small percentage of cells staining positive for CD29, CD90 and CD51/61, while staining negative for CD34 and CD45. At day 3, a significant enrichment of cells staining strongly for CD29, CD90 and CD51/61 was achieved. Gene expression patterns for bone growth factors and extracellular matrix molecules were found to be largely dependent upon the size of HA particles. Bone marker molecules, except OCN, had unaltered expression patterns in response to the varied size of HA particles. Overall, the results indicate that larger-sized HA particles upregulate PDGF and these groups were also associated with the most significant increase in osteodifferentiation markers, particularly ALP. Our results suggest that endogenous signalling is dependent upon material properties. Furthermore, we propose that studying gene expression patterns induced by the surrounding biomaterials environment is a fundamental step in the creation of engineered tissues.