Hydroxyapatite Nanopowders Research Articles

Toward an efficient antibacterial agent: Zn- and Mg-doped hydroxyapatite nanopowders

The use of synthetic hydroxyapatites (HAps) in biomedical and environmental applications is well warranted given that they have been shown to behave as an excellent bio-compatible material in human teeth and bones. In this paper, a series of HAps doped and co-doped with two metal cations (zinc and magnesium) has been successfully synthesized by means of the precipitation method using CaCl2, Na2HPO4, ZnCl2 and MgCl2 aqueous solutions as reagents. The synthesized samples have been characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). All samples prepared using over 10 mol% of Zn and Mg ions were identified as HAp. However, the presence of metal cations caused a significant increase in their crystallite sizes (30–50 nm) along with the appearance of a second phase (scholzite, whitlockite). The XRF spectra indicated the presence of Ca, P, Zn and Mg in the powders prepared with a high Metal/P ratio (1.7–2). The antimicrobial activity of these nanopowders has been tested in vitro against five bacteria (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa as Gram-negative; Staphylococcus aureus and Bacillus subtilis as Gram-positive) and two fungal strains (Candida albicans and Aspergillus niger). The outcomes revealed that these nanopowders exhibited strong antimicrobial activity, starting at 15 mol% of Zn and/or Mg.

Adsorptive removal of lead-210 using hydroxyapatite nanopowders prepared from phosphogypsum waste

Recently, several organic and inorganic adsorbents are used for the separation and purification processes of metal ions and removal of radionuclides from radioactive and industrial wastes. In this study, calcium hydroxyapatite was prepared by phosphogypsum waste and its adsorption behavior towards lead-210 was evaluated. Results showed that the adsorption percentage of hydroxyapatite was found to be 95% on the optimum conditions. Additionally, the adsorption kinetic data were analyzed using pseudo-first order and pseudo-second order kinetic models. The results indicated that hydroxyapatite is an efficient adsorbent for the removal of lead-210 from aqueous media with good performance.

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.

Large-scale and fast synthesis of nano-hydroxyapatite powder by a microwave-hydrothermal method.

A microwave-hydrothermal (M-H) method assisted with ultrasonic atomization precipitation was developed for large-scale and fast synthesis of nano-hydroxyapatite (nano-HAP) powder. This technology combines the uniform mixing effect of ultrasonic atomization precipitation at high concentration with the rapid and uniform heating effect of the M-H method, aiming to obtain a high quality product with low agglomeration, homogeneous size distribution, accurate stoichiometry, and high purity while improving the yield. The influences of reaction temperature, reaction time and reactant concentration on the formation of nano-HAP were investigated. The results show that the crystallinity increases significantly and the diameter of nano-HAP increases to some extent, but the length does not change obviously while the reaction temperature increase from 60 °C to 160 °C and the reaction time increases from 1 minute to 40 minutes respectively. The crystallinity, dispersion and crystal size of nano-HAP do not change obviously while the concentration of Na2HPO4·12H2O increases from 0.06 mol L−1 to 0.4 mol L−1. When the reaction temperature is 160 °C, the reaction time is 40 min, and the concentration of Na2HPO4·12H2O is 0.4 mol L−1, the yield of nano-HAP powder achieved a maximum yield (0.033 kg L−1). The obtained nano-HAP powder exhibits a uniform size and good dispersibility, with a size of 87.62 ± 22.44 nm and crystallinity of 0.92, respectively. This study indicates that the M-H method assisted with ultrasonic atomization precipitation is a facile one-pot method for the rapid and large-scale synthesis of highly crystalline, dispersible nano-HAP particles.

Characterization and influence of hydroxyapatite nanopowders on living cells.

Nanomaterials, such as hydroxyapatite nanoparticles show a great promise for medical applications due to their unique properties at the nanoscale. However, there are concerns about the safety of using these materials in biological environments. Despite a great number of published studies of nanoobjects and their aggregates or agglomerates, the impact of their physicochemical properties (such as particle size, surface area, purity, details of structure and degree of agglomeration) on living cells is not yet fully understood. Significant differences in these properties, resulting from different manufacturing methods, are yet another problem to be taken into consideration. The aim of this work was to investigate the correlation between the properties of nanoscale hydroxyapatite from different synthesis methods and biological activity represented by the viability of four cell lines: A549, CHO, BEAS-2B and J774.1 to assess the influence of the nanoparticles on immune, reproductive and respiratory systems.

Adsorption of Pb (II) Ions onto Hydroxyapatite Nanopowders in Aqueous Solutions.

Contamination of water with heavy metals such as lead is a major worldwide problem because they affect the physiological functions of living organisms, cause cancer, and damage the immune system. Hydroxyapatite, (Ca5(PO4)3OH) is considered one of the most effective materials for removing heavy metals from contaminated water. The hydroxyapatite nanopowders (N-HAp) obtained by a co-precipitation method were used in this research to determine the effectiveness in removing lead ions from contaminated solutions. In this study, we have investigated the structure and morphology of N-HAp nanopowders using X-ray diffraction (XRD), electronic transmission microscopy (TEM), and scanning electron microscopy (SEM). The structure information was also obtained by spectroscopy measurements. The Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy measurements revealed the presence of peaks corresponding to the phosphate and hydroxyl groups. The ability of N-HAp nanopowders to adsorb lead ions from aqueous solutions were established. The results of the kinetic and equilibrium studies on the removal of Pb (II) from aqueous solution revealed that the adsorption of lead (II) cations is due to the surface reaction with the hydroxyl terminal groups on the adsorbent and the combination of the positive charges of the metal cations with the negative charges on the adsorbent surfaces. These observations could validate the use of these ceramic nanopowders in ecological remediation strategies.

Preparation and Using Modified Nanohydroxyapatite Molecules for Wastewater Treatment

Today, the use of municipal wastewater (WW) as the alternative source of water for irrigation purpose is a common practice. This study will address the effect of using synthetic nanohydroxyapatite (nHAp) powders, which is prepared by microwave heating based wet chemical method and its modification with humic acid (HA) as a sorbent and stabilizing agents to remove contaminants from wastewater. The nHAp and nHAp-HA complex were characterized by different techniques. The wastewater treatment process was done by using a fixed bed column model by adsorption onto nHAp or nHAp-HA complex. The flow rate of the wastewater purification process was 80 ml/h for each 10 g of nHAp or nHAp-HA complex for treat 1 l. Some WW properties were determined before and after the treatment process, such as total organic carbon (TOC), heavy metals, major cations, major anions, electrical conductivity (EC), and pH. The results of this study indicated that TOC was completely removed from WW and removed by a 97.5% ratio by nHAp-HA complex and nHAp, respectively. In addition, cadmium, zinc, chromium, and lead were completely removed from the WW by a nHAp or nHAp-HA complex. Moreover, other heavy metals (copper, manganese, cobalt, iron, boron, and selenium), sodium adsorption ratio (SAR), total dissolved solids (TDS), EC, and pH of the treated wastewater (TWW) by the nHAp and modified nHAp were within the acceptable range of irrigation. Thus, nHAp and modified nHAp may be easily applied to treat the wastewater and be using it for irrigation purposes.

In vitro degradation and cytotoxicity of Mg-5Zn-0.3Ca/nHA biocomposites prepared by powder metallurgy

Abstract Mg-5Zn-0.3Ca/nHA biocomposites were prepared from pure Mg, Zn, Ca and nano-hydroxyapatite (nHA) powders by powder metallurgy method. The effect of various mass fractions of nHA (1%, 2.5%, 5%) as reinforcement on the corrosion properties of Mg-5Zn-0.3Ca alloy was investigated. The corrosion resistance of biocomposite samples was investigated by immersion tests and electrochemical techniques in SBF solution. The results showed that the corrosion resistance of Mg alloy was improved by adding 1% and 2.5% nHA. Bioactive nHA motivated the formation of stable phosphate and carbonate layers on surface and improved corrosion resistance of nanocomposites. However, addition of large contents of nHA in Mg alloy as reinforcement increased the density of this precipitated layer, so gases produced from localized corrosion were accumulated underneath this layer and decreased its adhesiveness and lowered its corrosion resistance. Indirect cytotoxicity evaluation for Mg alloy and its nanocomposites also showed that their extraction was not toxic and nanocomposite with 1% nHA indicated almost similar behavior as negative control.

Effects of ultrasonic agitation time on wet chemical synthesis of nanohydroxyapatite

In this study, the synthesis of the nanohydroxyapatite (nHAp) powders by way of wet chemical method is reported. Calcium nitrate tetrahydrate (Ca(NO3)2·H2O) and dibasic ammonium phosphate ((NH4)2HPO4) were used as calcium and phosphorus sources, respectively. The effect of ultrasonic agitation time has been systematically studied between 30 and 150 min at the temperature of 70°C. Structural, morphological, spectroscopic and thermal analysis have been carried out by way of X-ray powder diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy and thermogravimetry–differential scanning calorimetry analysis. It is shown that the ultrasonic agitation conditions significantly affect the crystallite size, dislocation density and microstrain of the powders calculated by way of the Debye–Scherrer formula. Thermal analyses reveal that the ultrasonic agitation treatment has a very beneficial effect on the fabrication of the powders by the wet chemical method due to the inhibition of physisorbed and chemisorbed water and the calcium deficiency. Magnetic stirring treatment is found to lead to larger nHAp nanoparticle agglomerations due to more water absorption. The results offer a promising route towards the scalable synthesis of the pure-phase nHAp powders with controllable structural and morphological properties, which could be useful in various types of basic and applied research on HAp-based materials.

Development of cerium and silicon co-doped hydroxyapatite nanopowder and its in vitro biological studies for bone regeneration applications

Multi-ion, co-substituted bioactive glass ceramics play a significant role in the stimulation of physical and biological properties for outstanding effects in biomedical application. The following work attempts to develop HAP as a parent material doped with a combination of cerium (Ce4+ @1.25 wt%) and silicon (Si4+ @1, 3 and 5 wt%) by refluxing based sol-gel technique. The anti-bacterial tests exhibit E. coli showing higher inhibition efficiency, in vitro hemolytic test exhibit good compatible nature of dual doped HAP with erythrocytes (<5% of hemolytic). In vitro bioactivity assay confirms that the developed dual doped HAP possesses excellent bone-like apatite layer formation on their surfaces. In vitro cellular study was performed for Ce/Si-HAP@5% powder against MG-63 cells, which demonstrated the good cell viability at higher concentrations (up to 800 µg/ml). Further, dual doped HAP powders were characterized by various analytical techniques such as ATR-FTIR, Powder-XRD, TGA-DTA, SEM-EDS, TEM and XPS analysis. The studies confirm that the synthesized dual doped HAP will act as better bioactive glass ceramics for potential orthopedic and dentistry applications.

Removal of Zinc Ions Using Hydroxyapatite and Study of Ultrasound Behavior of Aqueous Media.

The present study demonstrates the effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions. The synthesized hydroxyapatites before (HAp) and after the adsorption of zinc (at a concentration of 50 mg/L) in solution (HApD) were characterized using X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM, respectively). The effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions was stressed out through ultrasonic measurements. Both Langmuir and Freundlich models properly fitted on a wide range of concentration the equilibrium adsorption isotherms, allowing us to precisely quantify the affinity of zinc to hydroxyapatite nanopowders and to probe the efficacy of hydroxyapatite in removal of zinc ions from aqueous solutions in ultrasonic conditions.

The Influence of Scaffold Designs on Cell Seeding Efficiency in Establishing A Three-Dimensional Culture

The concept of Bone Tissue Engineering (BTE) based on cell-seeded scaffold holds great promise for the treatment of bone defects. However, much optimization is required in establishing a three-dimensional (3D) culture before BTE can be successfully applied clinically. In this study, we have assessed the influence of scaffold designs on the initial cell seeding efficiency of anchorage cells. The rapid prototyping designed polylactic acid (PLA) scaffolds fabricated using fused deposition modelling (FDM) designated by 2C and 4C scaffolds were compared to the commercial hydroxyapatite (HA) scaffold. Prior to cell seeding, 2C and 4C scaffolds were deposited with silicon carbonated HA nanopowders / Hyaluronic acid / Collagen Type I by Polyelectrolyte Multilayers (PEMs) coating and sterilized under ultra-violet (UV) radiation. Human Bone Marrow derived-Mesenchymal Stem Cells (hMSCs) were then cultured on the scaffolds using different volume of cell suspension, seeding method (one-side and two-sides; coated and non-coated well plates) and culture condition (static and rotary bioreactor). Regardless of scaffold designs, cell-seeded scaffold with small volume of cell suspension and two-sides seeding using coated well plate resulted in better cell attachment and distribution across the surface of the scaffolds than one-sided seeding. In any case, commercial HA exhibited lower percentages of cell attachment. Culturing these scaffolds in different media but culturing these scaffolds in rotary bioreactor has pronounced impact on the cell survival as compared to static condition.

Combined precipitation and spray drying for the synthesis of hydroxyapatite nanopowders as soft spherical granules

The aim of this study is to produce crystalline “hydroxyapatite” (HAp) nanopowders with very high “specific surface area” (SSA) as soft spherical granules in very small size. The HAp nanopowders were synthesized by sol-gel, biomimetic, gel combustion, precipitation and by “Combined Precipitation and Spray Drying” (CPSD). The properties of HAp nanopowders produced by these methods were investigated by XRD, FTIR, BET and SEM, and the results were compared. It was determined that synthesis process and drying conditions have very important influence on the properties of HAp nanopowders. The precipitate used as starting precursor for CPSD process was firstly synthesized by precipitation, and then it was ultrasonically dispersed in an ultrasonic bath assisted by mechanical stirring in order to prepare the “precipitate suspension like milk”, that will be referred to as “suspension” hereafter. Atomization of the suspension and direct drying of the sprays were carried out simultaneously using a spray dryer with a nozzle system at 180 °C. The HAp nanopowders synthesized by CPSD method have a crystalline structure with an average crystallite size of 15.6 nm, and have an average particle size of 15.7 nm with very high SSA (121.34 m2/g) in soft spherical granule form. HAp nanopowders which were synthesized by four other methods and dried at 110 °C have an average particle size larger than ≥ 24.6 nm in big, hard and shapeless agglomerate form with a SSA smaller than ≤ 77.43 m2/g. They attain a crystalline structure only after heat treatment at 600 °C. The application of CPSD process to produce the crystalline HAp nanopowders as soft spherical granules with very high SSA at very low temperature constitutes the originality of this study.

Biomineralization behavior of electrophoretic-deposited hydroxyapatite-tricalcalcium phosphate biphasic composite

Hydroxyapatite (HA) and tricalcium phosphate (TCP) coatings have been widely used as bonding layers on implants in the medical applications. In this research, nano-powders of HA is synthesized via aqueous sol-gel route. TCP is obtained by controlled heat treatment of HA phase at 700 °C. After that, these nano-powders are electrophoretically deposited on stainless steel substrates by applying 60 V for 5 min. Also, biphasic composite of these nano-powders are prepared at various HA/TCP ratios. The phase purity of HA and TCP are confirmed by means of X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis. Differential thermal analysis and thermogravimetry (DTA/TG) clearly demonstrate the thermolysis and phase formation for each phase. Fourier transformed infrared (FTIR) spectroscopy represents through elimination of unwanted ions. The electrophoretic deposition behavior of HA/TCP biphasic as well as single phase samples are compared and biomineralization test is performed by simulated blood fluid solution. The electrophoretic behavior of the samples dramatically changes by increasing the TCP content due to its larger particle. The HA films show higher thickness and lower porosity, which are gradually changes by increasing TCP content. In terms of biomineralization, suitable growth occurs in all samples. However, the most appreciable growth is taken place in HA:TCP ratio of 25:75 wt%. These results show that the biphasic HA/TCP coatings, if appropriately applied on implants by simply controlling the electrophoretic deposition parameters, can enormously improve the grafting process by combining the TCP reactivity to form porous structure and providing required species and the HA biocompatibility and strength to bond to adjacent tissues.

Differentiation of Periodontal Ligament Stem Cells Into Osteoblasts on Hybrid Alginate/ Polyvinyl Alcohol/ Hydroxyapatite Nanofibrous Scaffolds

: The efficacy of Alginate/ Polyvinyl alcohol/ Hydroxyapatite nanopowders (Alg/PVA/HANPs) mats was investigated for increasing periodontal ligament stem cells (PDLSCs) differentiation into the osteoblast cells. The Alg/PVA/HANPs nanofibers were fabricated through electospinning process and following ionic crosslinking of Ca+2 and glutaraldehyde crosslinkers. The physical features of mats and expression of osteoblast cell markers were evaluated. Results showed the diameter of nanofiber increases with decreasing the incorporation of HANPs in Alg/PVA nanofiber. According to MTT assay the viability of cells on scaffolds are better in the all of groups, so the scaffolds were not toxic for the cultured cells. The osteogenic culture media appropriately enhanced osteopontin and osteocalcin markers. Furthermore, in vitro study indicated that the Alg/PVA/HANPs nanofiber provided a suitable three-dimensional structure for osteoblast cells differentiation. Thus, the Alg/PVA/HANPs scaffold can be recommended for in bone repair.

Effect of Joncryl61 and gelatin in the formation of hydroxyapatite nanocomposite

Hydroxyapatite (HAp) is a bioceramic known for bone applications due to its physical and chemical properties similar to the human bone. In this present study, HAp nanopowder was synthesised using chemical precipitation method in the presence of polymers Joncryl61 (acrylic resin) and gelatin (biopolymer). The crystalline nature of synthesised pure and polymer-added hydroxyapatite was confirmed by powder X-ray diffraction pattern and the FTIR pattern peaks present at 604–624 cm−1 revealing the presence of phosphate phase. Morphological studies using SEM revealed the presence of rod-shaped, agglomerated rod-shaped and rod shape with small sphere dumbbell structure in pure HAp, HAp with Joncryl61 and HAp with gelatin respectively. The dielectric properties of pure and polymer-doped HAp were also examined at room temperature with frequency from 50 to 5,000,000 Hz. The dielectric constant and loss were found to be maximum when the frequency was low.

Sinterability of Magnesium Hydroxyapatite Bioceramic and Its Mechanical Properties

One of the most favoured material in bone tissue engineering field nowadays is hydroxyapatite (HA), which is also known to be bioactive and has a similar composition to human bone. However, developing an artificial bone or bone graft using biocompatible HA is a challenging task due to the lower strength of the main substance. To improve the mechanical properties of synthetic HA, introduction of metallic substance such as magnesium (Mg) into HA has been proposed. In this present study, 0, 10 15 wt% of magnesium hydroxyapatite (MgHA) nanopowders were prepared by a simple wet precipitation method. These nanopowders were then compacted using a 10-ton compression uniaxial press machine with 150 MPa pressure to form a disc shape of dense MgHA. After that, the MgHA discs were sintered at a temperature of 1000 °C and 1100 °C to remove the organic compounds and further densify the ceramics. XRD results showed that the crystallinity of MgHA increased when the sintering temperature increases. The compression test showed that the 10 wt% MgHA sample recorded the highest compressive strength (243.59 MPa) when sintered at 1100 °C, while pure HA has the lowest value with 49.37 MPa. This study also demonstrates that sintering temperature at 1100 °C gives significant improvement to the mechanical properties of the MgHA dense bodies compared to sintering at 1000 °C.

Effect of conventional and microwave heating on the structural and physicochemical properties of silver-doped hydroxyapatite nanopowders

ABSTRACTThis paper discussed the influence of duration and modes of heating on structural and physicochemical properties of silver-doped hydroxyapatite (Ag-HAP) nanopowders (NPs). Conventional electric furnace and microwave (MW) heating modes were employed during the synthesis. MW mode of synthesis was relatively an efficient method as it prepared monolithic HAP NP in just one minute of heating. With the increase in duration of heating in both modes of heating; lattice parameters, crystal size, lattice strain, Ca/P ratio, and degree of crystallinity of HAP phase increased. The morphology of particles was rod-shaped having aspect ratio between 2 and 3. EDX confirmed the presence of Ag and corroborated the formation of apatite. The hydrodynamic diameter of Ag-HAP NPs was significantly bigger than the particle sizes calculated using XRD, FESEM, and TEM. Thus, an overall examination concluded MW as an efficient mode of synthesis, able to produce Ag-HAP NPs in a possible minimum time.

Kinetic Studies of Zn(II) Removal from Single and Binary Solutions by Synthetic Hydroxyapatite - Based Nanopowders

A kinetic study has been carried out with two hydroxyapatite nanopowders to establish the mechanism involved in heavy metals removal from aqueous synthetic solutions. The samples of nanohydroxyapatite have been previously characterized. The first sample represents a pure hydroxyapatite (HAP) nanopowder named HAP-1, and the second sample (HAP-2) consist of a mixture of hydroxyapatite (HAP; Ca10(PO4)6(OH)2) and b-tricalcium phosphate (b-TCP; Ca3(PO4)2). Batch experiments with single and binary Zn(II) and Pb(II) aqueous solutions have been performed. According to this research study, it was found that the both nanohydroxyapatite samples show good heavy metals adsorption capacity, and selectivity for Pb(II) ions. A more pronounced decreasing of sorption capacity of Zn(II) ions from binary solutions compared to that registered from single heavy metal ion solutions has been observed. From the kinetic point of view, the sorption process can be described for both heavy metals as a pseudo-second-order kinetic process. According to this model, the Zn(II) and Pb(II) sorption can be achieved by chemical reactions between heavy metals and functional groups of adsorbents. The obtained results are indicative of good hydroxyapatite adsorption ability towards Pb(II) and Zn(II) ions.

Influence of pH on wet-synthesis of silver decorated hydroxyapatite nanopowder.

Here, effect of solution pH on precipitation of silver decorated hydroxyapatite (Ag-HAp) nano powder during its wet-synthesis was systematically studied. XRD pattern of Ag-HAp nano powder synthesised at pH ranging from 5 to 10 shows that calcium hydrogen phosphate was formed as dominating phase when the solution pH was between 5 and 9 and this phase was gradually transformed into a stable HAp above pH 9. A quantitative analysis of silver amount in Ag-HAp nano powder synthesised at different pH showed that silver can be precipitated to its maximum amount at pH 8 and the further addition of ammonia leads to the formation of a silver-ammonium complex, thereby remaining in the solution. HR-TEM and XPS analysis further confirmed the presence of silver in HAp nanocrystals, synthesised at an optimum pH 9. This trace amount of silver in HAp nano powder showed effective antibacterial activity against Staphylococcus aureus and Escherichia coli. In addition, the cytocompatibility studies carried out on MG63 cells further confirmed the present optimised silver concentration of the Ag-HAp nano powder is well within the toxic limit to be useful in various biomedical applications.