Hydroxyapatite Nanopowders Research Articles

Cerium substituted hydroxyapatite mesoporous nanorods: Synthesis and characterization for drug delivery applications

Hydroxyapatite with desirable properties is considered to be important biomaterial offering viable replacement for damaged hard tissues of human body. Substituting hydroxyapatite with suitable ions is one of the method to govern its properties. This paper reported the cerium substituted hydroxyapatite with mesoporous rod-like morphology under microwave synthesis. The effect of cerium substitution on physio-chemical properties of synthesized nanopowders was characterized using XRD, FTIR, HRTEM, EDX, BET analysis. Results reported successful substitution of cerium into HAP crystal structure as evident by XRD and FTIR. HRTEM images reports nanorods morphology with average length and diameter of 60 ± 18 nm and 18 ± 4 nm respectively for Ce-HAP particles. Mesoporous structure was confirmed by BET analysis with pore volume 0.152 cm3/mg and 7–8 nm average pore diameter. Further exploring the drug delivery potential, cerium substituted nanopowders exhibited 43% more drug loading ability as compared to Pure-HAP powder, whereas the drug discharge behaviour exhibited preliminary fast release followed by persistent release of ibuprofen drug. This, established the ability of cerium substituted hydroxyapatite nanopowders with custom properties for hard tissue engineering and drug delivery agents for treatment of infection and long term healing.

Evaluation of Osteoblast-like Cell Responses to Surfaces Patterned with Hydroxyapatite Nanopowders on Ti Surfaces

Evaluation of Osteoblast-like Cell Responses to Surfaces Patterned with Hydroxyapatite Nanopowders on Ti Surfaces

On the machinability and properties of Ti-6Al-4V biomaterial with n-HAp powder-mixed ED machining.

Nano-hydroxyapatite powder was used in electric discharge machining to modify the surface of Ti-6Al-4V medical alloy. Herein, electric discharge machining was performed, with and without powder-mixed flushing for evaluation of the material erosion rate and surface roughness. In addition to dielectric type, several process parameters including current, pulse-on duration, pulse-off duration, and electrode hole diameter were considered. The experiments were planned by Taguchi design technique and conducted to analyze the material erosion rate and surface roughness. After machining, scanning electron microscope, energy-dispersive X-ray spectrometry, and X-ray diffraction techniques were used to evaluate the surfaces of the samples. Furthermore, wear and corrosion tests were also carried out on the Ti alloy with modified surfaces. The influential factors were identified based on analysis of variance results. Current and dielectric type were the significant factors, both for the material erosion rate and surface roughness. The scanning electron microscope images of Ti-6Al-4V samples highlighted that the process parameters exhibited a vital influence on the topology and microstructure of machined surface. Furthermore, energy-dispersive X-ray spectrometry and X-ray diffraction analyses confirmed the presence of hydroxyapatite on Ti alloy surface after machining. Moreover, the results of wear and corrosion tests revealed lower wear and corrosion rates of the surface-treated workpiece with nano-hydroxyapatite.

SURFACE MORPHOLOGY AND MICROHARDNESS BEHAVIOR OF 316L IN HAP-PMEDM

The development of biomaterials for implants nowadays requires materials with superior mechanical and physical properties for enhanced osseointegration and sustained longevity. This research work was conducted to investigate the influence of nano hydroxyapatite (HAp) powder mixed electrical discharge machining (PMEDM) on surface morphology and microhardness of modified 316L stainless steel surface. The chosen process parameters were discharge current, pulse on/off duration and gap voltage in order to analyze the selected output responses. HAp concentration (15 g/l) along with reverse polarity was kept constant for current experimentation. The experimental results testified that surface morphology of PMEDM surface was significantly improved along with augmentation of 79% in microhardness (HV) of HAp modified surface of medical grade stainless steel. Furthermore, XRD and SEM characterization confirmed the deposition of calcium, phosphorous and inter-metallic compounds on HA-PMEDMed surface. The surface thus produced is expected to facilitate better bone-implant adhesion and bioactivity.

A Review on Lead Sources, Occurrences, Health Effects, and Treatment Using Hydroxyapatite (HAp) Adsorbent Made from Fish Waste

The issues of heavy metal contamination in water sources have been increasing substantially along with the rapid pace of industrial revolution. Lead, particularly, is one of the heavy metals that received considerable attention lately due to its frequent detection in the environment and hazardous effects. Although conventional water treatment processes had been utilized for ages, it is still a challenge to remove lead in the treatment plant effectively. In line with the advancement of chemistry and nanotechnology, the study on hydroxyapatite (HAp) nanopowder made from fish waste (skin, bones, and scales) has brought to its beneficial use as an adsorbent for lead removal in water. This paper reviews on the sources, occurrences, and health effects of lead as well as the treatment of lead using HAp adsorbent for its removal in water.

Analysis of antibacterial activity and cytotoxicity of silver oxide doped hydroxyapatite exposed to DC glow discharge plasma

The present work investigated the possibility of enhancing hydroxyapatite (HAp) bioactivity by substituting silver oxide. Ag2O-HAp nanoparticles were synthesized by using the wet precipitation process with exposure to DC glow discharge non thermal plasma. The phase purity, elemental composition and morphology were analyzed by XRD, FTIR, SEM and EDX. MTT assay for Silver oxide doped hydroxyapatite (Ag2O HAP) nanopowders (NPs) have been carried out for MCF-7 breast cancer cell line and the cyototoxicity effect were analysed. The biocompatibility of the synthesized silver oxide doped HAp proves it as promising candidate for upcoming biomedical applications.

Structural modification of nanohydroxyapatite Ca10(PO4)6(OH)2 related to Eu3+ and Sr2+ ions doping and its spectroscopic and antimicrobial properties

The Eu3+ and Sr2+ ions co-doped hydroxyapatite nanopowders (Ca10(PO4)6(OH)2) were synthesized via a precipitation method and post heat-treated at 500 °C. The concentration of Eu3+ ions was established in the range of 0.5–5 mol% to investigate the site occupancy preference. The concentration of Sr2+ ions was set at 5 mol%. The structural and morphological properties of the obtained materials were studied by an X-ray powder diffraction, a transmission electron microscopy techniques and infrared spectroscopy. As synthesized nanoparticles were in the range of 11–17 nm and annealed particles were in the range of 20–26 nm. The luminescence properties in dependence of the dopant concentration and applied temperature were investigated. The 5D0 → 7F0 transition shown the abnormally strong intensity for annealed materials connected with the increase of covalency character of Eu3+–O2− bond, which arise as an effect of charge compensation mechanism. The Eu3+ ions occupied three possible crystallographic sites in these materials revealed in emission spectra: one Ca(1) site with C3 symmetry and two Ca(2) sites with Cs symmetry arranged as cis and trans symmetry. The antibacterial properties of Eu3+ and Sr2+ ions doped and co-doped hydroxyapatite nanopowders were also determined against Gram-negative pathogens such as Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli. Obtained results suggest that both europium and strontium ions may implement antibacterial properties for hydroxyapatites. In the most cases, better antibacterial effect we noticed for dopants at 5 mol% ratio. However, the effect is strongly species- and strain-dependent feature.

Synthesis of Magnesium- and Silicon-modified Hydroxyapatites by Microwave-Assisted Method

Nanopowders of hydroxyapatite (HA), modified by magnesium (MgHA) and by silicon (SiHA) were obtained by liquid-phase microwave synthesis method. X-ray diffraction and IR spectroscopy results showed that Mg2+ and SiO44− ions were present in the synthesized products both as secondary phases and as part of the HA phase. Whitlockite was found in the magnesium-modified HA (MgHA) and larnite was found in the silicon-modified HA (SiHA); ion substitution for both materials resulted in solid solutions. In the synthesized samples of modified HA, the increase of particle size of powders was in the order HA < SiHA < MgHA, which was calculated through data specific surface area and measured pycnometric density of the powders. The Lewis acid sites (Ca2+, Mg2+, Si4+) were present using spectral probes on the surface of the samples of HA, MgHA, and SiHA, and the acidity of these sites decreased in the order SiHA > MgHA > HA. The rates of calcium phosphate layer deposition on the surface of these materials at 37 °C in the model simulated body fluid solution showed similar dependence.

Influence of Al on the Structure and in Vitro Behavior of Hydroxyapatite Nanopowders.

Nanopowders of aluminum-substituted (0-20 mol %) hydroxyapatite (HA) with the average size of 40-60 nm were synthesized by the precipitation method from nitrate solutions. A series of samples were studied by various analytical tools to elucidate the peculiarities of Al introduction. Electron paramagnetic resonance and pulsed electron-nuclear double resonance data demonstrate that incorporation of Al resulted in a decrease in the concentration of impurity carbonate anions and lead to an increase in the number of protons in the distant environment of the impurity nitrogen species. Density functional theory calculations show that the Al3+ incorporation is accompanied by the local positional rearrangement and the distortion of anion channel geometry. An in vitro test conducted on MG-63 cells demonstrates the cytocompatibility and magnification of the surface matrix characteristics with Al doping.

Secretion of Hematopoietic Niche Signal Molecules under Conditions of Osteogenic Differentiation of Multipotent Mesenchymal Stromal Cells Induced By Relief Calcium Phosphate Coating

Using a multiplex kit the secretion of a number of cytokines, chemokines, and growth factors has been investigated in vitro in a culture of human adipose-derived multipotent mesenchymal stromal cells (hAMMSCs) under conditions of their osteogenic differentiation caused by 14-day contact with a calcium phosphate (CP) surface of different roughness. Bilateral X-ray amorphous CP coatings were prepared on the samples of commercially pure titanium in the anodal regime using a microarc method. The electrolyte consisted of aqueous orthophosphoric acid (20 wt %), calcium carbonate (9 wt %), and synthetic hydroxyapatite nanopowder (6 wt %, particle diameter of 10–30 nm with single agglomerates up to 100 nm). hAMMSCs isolated from lipoaspirate were co-cultured after 4 passages with the CP-coated samples at a final concentration of 1.5 × 105 viable karyocytes per 1.5 mL of standard nutrition medium (without osteogenic stimulators) for 14 days (determination of the [CD45,34,14,20], CD73, CD90, and CD105 cell immunophenotype; analysis of secretory activity) and 21 days (alizarin red S cell culture staining) with medium replacement every 3–4 days. Under conditions of in vitro contact with rough CP coating hAMMSCs differentiated into osteoblasts synthesizing the mineralized bone matrix; this was accompanied by a 2−3-fold increase in the proportion of [CD45,34,14,20]+ hemopoietic cells. The following humoral factors of hemopoietic niches acted as the signal molecules escalating in vitro the hemopoietic base in 14 days of differentiating three-dimensional culture of hAMMSCs: leukemia inhibitory factor (LIF) and stem cell factor (SCF) cytokines in the case of the mean index of CP roughness Ra = 2.4–2.6 µm or stromal derived factor-1 (SDF-1α, CXCL12 chemokine) in the case of Ra = 3.1–4.4 µm.

Structural, optical, and luminescence properties of Cu2+-doped Ca-Li hydroxyapatite nanopowders prepared by mechanochemical synthesis

Novel luminescent phosphor materials have potential applications in lighting, display devices, and optical communication. In this study, novel Cu2+-doped calcium-lithium hydroxyapatite (CLHA) nanopowders were successfully fabricated by a simple mechanochemical technique. The synthesized samples were characterized by several microscopic and spectroscopic techniques. The hexagonal phase of the prepared sample was confirmed by x-ray diffraction results, and the average crystallite sizes were evaluated. Fourier transform infrared spectra demonstrated the formation of numerous vibrational modes ascribed to phosphate molecules and other hydroxyl groups. The morphologies of the Cu2+-doped CLHA nanopowders were investigated by scanning electron microscopy and transmission electron microscopy analyses. Optical absorption and electron paramagnetic resonance data indicated that the distortion of Cu2+ in the host lattice corresponds to the tetragonal site symmetry. Photoluminescence (PL) spectra of the Cu2+-doped CLHA nanopowders revealed strong blue and weak green emission peaks. From the PL emission spectra, the chromaticity CIE parameters were evaluated, and the results indicated that the prepared phosphor materials may be useful for lighting and display devices.

Hydroxyapatite-embedded monolithic column for selective on-line solid-phase extraction of adenosine triphosphate and its phosphorylated metabolites

A novel hydroxyapatite-embedded monolithic column has been facilely prepared in a stainless-steel column with inner diameter of 2.1 mm by the strong adhesion of urea-formaldehyde (UF) resin and exploited as a sorbent for selective on-line solid-phase extraction (on-line SPE) of adenosine triphosphate and its phosphorylated metabolites. The composition for this preparation, including the amount of hydroxyapatite nanopowders and the porogen were investigated to obtain a suitable monolith with large surface area and satisfactory permeability. Owing to anion exchange interaction of hydroxyapatite and hydrophilic interaction of UF monolithic matrix, the prepared monolith showed good extraction efficiency and selectivity towards these phosphorylated analytes. Several parameters for on-line SPE, including ACN percentage in the sampling solution, collection time span, salt concentration of the eluent, sampling and elution flow rate, were optimized with respect to the extraction efficiencies of the target compounds. Under the optimized conditions, the LODs of the analytes were in the range of 0.01–0.04 μg/g, the recoveries in the spiked samples ranged from 78.3%–92.5% with RSDs <4.7%. Due to the excellent extraction ability towards phosphorylated compounds in practical samples, a simple on-line SPE-HPLC method using hydroxyapatite-embedded monolith as sorbent has been proposed for monitoring freshness of grass carp.

3D structures of hydroxyapatite obtained from Rapana venosa shells using hydrothermal synthesis followed by 3D printing

In this study, hydroxyapatite (HAp) obtained by hydrothermal synthesis from natural sources (whelk shells of Rapana thomasiana) was compared to synthetic hydroxyapatite (prepared from chemical reagents) and used for 3D printing of HAp-based structures. Rapana thomasiana can be found in Romanian coast of Black Sea. The visceral part of Rapana is used for culinary purposes, but the whelk shell, mainly consisting of CaCO3, remains as biowaste and can be used as a source of Ca for hydroxyapatite synthesis. Synthetic and natural hydroxyapatite nanopowders were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), dynamic light scattering (DLS) method and in vitro tests. XRD and FT-IR have confirmed the formation of nanostructured hydroxyapatite irrespective of the raw material used. Both types of powders were further used for 3D printing of HAp-based structures, which have also been characterized by SEM and in vitro tests. In vitro tests performed on natural HAp disks (made from whelk shell) lack cytotoxicity and were associated with cell viability similar to that for the synthetic hydroxyapatite disk.

Optimizing tribological, tensile & in-vitro biofunctional properties of UHMWPE based nanocomposites with simultaneous incorporation of graphene nanoplatelets (GNP) & hydroxyapatite (HAp) via a facile approach for biomedical applications

The present study focuses on simultaneous influence of graphene nanoplatelets (GNP) and hydroxyapatite (HAp) nanopowder on microstructural, wear, tensile and biofunctional behavior of UHMWPE based nanocomposites used in biomedical applications, with the aim to utilize GNP's mechanical strength and wear resistance, while benefitting from HAp's biocompatibility at the same time. 0.1, 0.5 and 1 wt% GNP with 10 wt% optimized concentration of HAp were added to the UHMWPE matrix through an easy two-step approach consisting of solvent mixing and ultrasonication in ethanol as a liquid media. The dried nanocomposite samples of powder were then hot pressed at an optimized temperature and pressure to ensure complete melting and flowing of the polymeric material. Tensile testing results indicated a 114% & 24% increase in elastic modulus and yield strength in the sample containing 1 wt% GNP and 10 wt% HAp, respectively, as compared to UHMWPE. However, the sample containing 0.5 wt% GNP showed greatest tensile performance with an increase of 101% and 31% improvement in elastic modulus and yield strength, which proves that the strengthening mechanism is influenced by the content of the reinforcement, especially in case of 2D reinforcing phases such as GNP. Microstructural analysis revealed the nucleating effect of GNPs on the crystalline structure of UHMWPE, to which the escalated mechanical properties could be attributed. Furthermore, the assessments disclosed the dependency of nucleating, and in consequence strengthening effect of GNPs to their concentration and apparent clustering threshold. Moreover, pin-on-disk tribological testing results showed a somewhat similar result for the coefficient of friction, which decreased by 50% with 1 wt% GNP, while the similar parameter for the sample containing 0.5 wt% GNP underwent 54% reduction. Whereas a steady decreasing pattern was observed in the case of wear rate with an 82% decrease in the sample containing 1 wt% GNP, coming to a conclusion that GNP is much more effective in improving wear properties rather than in mechanical strengthening. Biological examinations also demonstrated that HAp promises biocompatibility, osteoconductivity and the elimination of adverse cellular response, while cell adhesion was still dependent on the concentration and was affected adversely with increasing GNP. This destructive biological effect of GNPs was seemingly attributed to the functional groups of the material, or to the inherent edge-shaped structure by means of FTIR, wettability and compaction analyses.

An artificial blood vessel fabricated by 3D printing for pharmaceutical application

Objective(s): Cardiovascular diseases (CVDs) are the leading cause of mortality in the elderly. A common medical procedure for the treatment of CVDs is the replacement of the blocked or narrowed arteries, which is currently the optimal vascular transplant associated with autograft transplantation. In general, the saphenous veins and radial arteries in the mammary gland are considered to be the selective vessels for vascular substitution. In many cardiac patients, artificial blood vessels (ABVs) are not used for several reasons, including the age of the patient, small size of the veins, previous impressions, and abnormally. Therefore, the consideration of vascular substitute demands is inevitable, especially regarding vascular transplantation with very small diameters and availability of proper alternatives. The present study aimed to develop a novel artificial bio-composite blood vessel using polymer-reinforced and bioceramic nanoparticles. Materials and Methods: The biomechanics and chemical properties of artificial vessels have been investigated to be used in coronary artery bypassing in atherosclerosis as a soft tissue engineering procedure. In this study, thermoplastic polyurethane (TPU) composed of nanocrystalline hydroxyapatite (HA) nanopowder was prepared using the extrusion technique to construct the ABVs. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the optimum specimen. An important feature of the ABVs was the ability to find the elastic modulus, wettability, and porosity of the veins, which were assessed by fused deposition modeling and 3D printing. Results: The sample containing five wt% of HA had superior mechanical and biological features over the pure sample. Conclusion: According to the results, the narrowed arteries composed of TPU composite with nanocrystalline HA nanopowder had proper chemical stability and mechanical characteristics.

Suspension Detonation Spraying of Ceramic Coatings

Experiments on detonation spraying of ceramic coatings are for the first time carried out by feeding a powder as a part of a suspension into a barrel. Spraying of Al2O3, TiO2, and hydroxyapatite nanopowders shows that the new method for obtaining coatings (suspension detonation spraying) can be implemented on a CCDS2000 detonation device. Unlike conventional detonation spraying technologies using micron-sized powders, suspension spraying makes it possible to work with powders whose particle size is smaller than a micron and which serve as a basis for preparing a suspension injected into the detonation device barrel.

Tuning mechanical reinforcement and bioactivity of 3D printed ternary nanocomposites by interfacial peptide-polymer conjugates

We present a study on ternary nanocomposites consisting of medical grade poly(ε-caprolactone) (mPCL) matrix, hydroxyapatite nanopowder (nHA) and compatibilized magnesium fluoride nanoparticle (cMgF2) fillers. MgF2 nanoparticles were compatibilized by following a design approach based on the material interfaces of natural bone. MgF2-specific peptide-poly(ethylene glycol) conjugates were synthesized and used as surface modifiers for MgF2 nanoparticles similarly to the non-collagenous proteins (NPC) of bone which compatibilize hydroxyapatite nanocrystallites. Different compositions of mPCL/nHA/cMgF2 composites were blended together and processed into three dimensional (3D) scaffolds using solvent-free techniques including cryomilling and melt extrusion-based additive manufacturing. The use of two different inorganic fillers in mPCL resulted in nanocomposite materials with enhanced mechanical and biological properties. In particular, cMgF2 nanoparticles were found to be the primary constitent leading to the significant improvements in the mechanical properties of these composites. The scaffolds of the ternary nanocomposites provided the best in vitro performance in terms of osteogenic differentiation and stimulated mineralization. In summary, we demonstrated that the concept of bioinspired interface engineering facilitates the development of homogeneous ternary nanocomposites with increased processability in additive biomanufacturing. Additionally, the concept leads to scaffolds exhibiting enhanced mechanical and biological properties. Overall, these multicomponent nano-interfaced building blocks add a new group of advanced functional materials with tunable mechanical properties, degradation and bioactivity.

Synthesis and characterization of fluoridated hydroxyapatite nano-powder via microwave irradiation method

Fluoridated hydroxyapatite (FHA) occur in teeth and form the basis for application as a biomaterial. This work aims to synthesize and analyze the characteristic of FHA nano-powder with different degrees of fluoridation via microwave irradiation method. FHA nano-powder with a chemical formula of Ca10(PO4)6(OH2-x)Fx (where degrees of fluoridation, x values were selected equal to 0.7 and 1.3) were synthesized using a mixture of calcium hydroxide, diammonium hydrogen phosphate, and ammonium fluoride solutions by utilizing microwave with the variation of irradiation power. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy analysis techniques were utilized in order to evaluate the characteristic of synthesized FHA nano-powder. The XRD and FTIR results confirmed highly crystalline FHA powder with the carbonate peaks in the IR spectrum. Using a Scherrer formula, the average crystallite size was found to be 30 nm. The SEM and EDX results indicated various element composition and several morphologies with the lattice parameter increased along with irradiation power. FHA nano-powder could be synthesized via microwave irradiation method. The results from different kind of analysis illustrated that synthesized FHA nano-powder could fulfill the requirement of ASTM F1185-88 for used as biomaterial.

Immobilization of radioactive corrosion products by cold sintering of pure hydroxyapatite.

An efficient method for the consolidation of cobalt (Co(II)) adsorbed calcium hydroxyapatite was investigated to develop a simplified route for decontamination of the coolant system of nuclear power plants and direct immobilization of as-spent adsorbent. Calcium hydroxyapatite nano-powder synthesized by a wet precipitation method was used as an adsorbent and 94% Co(II) surrogate removal from simulated water was measured. The as-spent adsorbent was sintered at 200 °C, a temperature significantly lower than conventional sintering temperatures (900-1300 °C) for hydroxyapatite, under a uniaxial pressure of 500 MPa for 10 min. The relative density after the cold sintering was >97% and sintered samples displayed good compressive strength (175 MPa). The normalized leaching rate of the Co(II) was measured as per ASTM-C1285 standard and found to be 2.5 × 10-5 g/m2/day. ANSI/ANS-16.1 test procedure was used to analyze the leachability of the sintered matrices and the measured leaching index value was 6.5. Thus, the use of pure calcium hydroxyapatite nano-powder as adsorbent and its cold sintering offers a mean by which radioactive waste form can be processed in an environment friendly manner.

Development of sulfonate-functionalized hydroxyapatite nanoparticles for cadmium removal from aqueous solutions

Sulfonate-functionalized hydroxyapatite was successfully synthesized by organo-functionalization using natural phosphate and Benzenedisulfonate molecules. The modified apatites were characterized using multiple techniques, evidencing the effective incorporation of organo-functional groups into the hydroxyapatite matrix. Sulfonated mesoporous hydroxyapatite possesses a large amount of accessible -SO3 acid groups, which may be versatile adsorbents for the binding of Cd (II) cations. Stability issues of the sulfonated HAp nanocomposites for the specific reactions are addressed. The sulfonated hydroxyapatite nanopowders were evaluated cadmium removal from water. Adsorption tests reveal the efficiency of the hybrid apatites for cadmium removal (qm = 457 mg g−1). Experimental results fit the Ho-second-order kinetic model for chemical adsorption. Two possible adsorption controlled mechanisms of Cd (II) ions at the apatite surface, complexation and dissolution/precipitation, are proposed.