Hydroxyapatite Nanopowders Research Articles

Porous Biphasic Calcium Phosphate Granules from Oyster Shell Promote the Differentiation of Induced Pluripotent Stem Cells.

Oyster shells are rich in calcium, and thus, the potential use of waste shells is in the production of calcium phosphate (CaP) minerals for osteopathic biomedical applications, such as scaffolds for bone regeneration. Implanted scaffolds should stimulate the differentiation of induced pluripotent stem cells (iPSCs) into osteoblasts. In this study, oyster shells were used to produce nano-grade hydroxyapatite (HA) powder by the liquid-phase precipitation. Then, biphasic CaP (BCP) bioceramics with two different phase ratios were obtained by the foaming of HA nanopowders and sintering by two different two-stage heat treatment processes. The different sintering conditions yielded differences in structure and morphology of the BCPs, as determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) surface area analysis. We then set out to determine which of these materials were most biocompatible, by co-culturing with iPSCs and examining the gene expression in molecular pathways involved in self-renewal and differentiation of iPSCs. We found that sintering for a shorter time at higher temperatures gave higher expression levels of markers for proliferation and (early) differentiation of the osteoblast. The differences in biocompatibility may be related to a more hierarchical pore structure (micropores within macropores) obtained with briefer, high-temperature sintering.

The Effect of Addition of Nano hydroxyapatite Powder of Anadara granosa Shells on Surface Roughness of Heat-cured Acrylic Resin

Background: Heat-cured acrylic resin is one of the most widely used denture base materials. However, the residual monomer can reduce its mechanical properties, which affect physical properties such as surface roughness, resulting in high porosity—the results in the growth of fungal colonies. One way to improve these properties is to add a reinforcement material such as nano-hydroxyapatite (HAp) from the Anadara granosa shell. Nano-hydroxyapatite has a large surface area to act as a filler because of its strong bonding capacity and a smoother surface, and a higher density to improve mechanical properties. Purpose: This study aims to determine HAp powder's effect from the Anadara granosa shells on the surface roughness of heat-cured acrylic resin. Methods: This type of research used an experimental laboratory, research design posttest-only control group design. Twenty-four samples were used and divided into three groups: the acrylic resin group with 1%, 3% blood cockles shell HAp, and acrylic resin without HAp with simple random sampling. Results: The results showed that the lowest mean value of surface roughness was in a group with the addition of 3% HAp, at 1.696 ± 0.25058 µm. One-Way ANOVA test on roughness showed a significant difference between groups with p = 0.000 (p <0.05). Conclusion: This study concludes that there is an effect of HAp on the roughness of heat-cured acrylic resin.

Hydroxyapatite-Decorated Fmoc-Hydrogel as a Bone-Mimicking Substrate for Osteoclast Differentiation and Culture

Hydrogels are water-swollen networks with great potential for tissue engineering applications. However, their use in bone regeneration is often hampered due to a lack of materials’ mineralization and poor mechanical properties. Moreover, most studies are focused on osteoblasts (OBs) for bone formation, while osteoclasts (OCs), cells involved in bone resorption, are often overlooked. Yet, the role of OCs is pivotal for bone homeostasis and aberrant OC activity has been reported in several pathological diseases, such as osteoporosis and bone cancer. For these reasons, the aim of this work is to develop customised, reinforced hydrogels to be used as material platform to study cell function, cell-material interactions and ultimately to provide a substrate for OC differentiation and culture. Here, Fmoc-based RGD-functionalised peptide hydrogels have been modified with hydroxyapatite nanopowder (Hap) as nanofiller, to create nanocomposite hydrogels. Atomic force microscopy showed that Hap nanoparticles decorate the peptide nanofibres with a repeating pattern, resulting in stiffer hydrogels with improved mechanical properties compared to Hap- and RGD-free controls. Furthermore, these nanocomposites supported adhesion of Raw 264.7 macrophages and their differentiation in 2D to mature OCs, as defined by the adoption of a typical OC morphology (presence of an actin ring, multinucleation, and ruffled plasma membrane). Finally, after 7 days of culture OCs showed an increased expression of TRAP, a typical OC differentiation marker. Collectively, the results suggest that the Hap/Fmoc-RGD hydrogel has a potential for bone tissue engineering, as a 2D model to study impairment or upregulation of OC differentiation.

Multifunctional strontium-sulphate co-substituted hydroxyapatite nanopowders

The development of materials having customized properties to suit any therapeutic environment has been a dream for a long. Hydroxyapatite (HAP) as a biomaterial offers excellent ionic substitution flexibility, propagating numerous materials with desirable behavior. The present work reports the co-substitution of strontium and sulphate into HAP structure by microwave synthesis to obtain the nanopowders blended with useful properties for combined antibacterial and drug delivery applications. The XRD, FTIR, HRTEM, EDX, TGA, and BET techniques were employed to investigate the structure of strontium-sulphate (SrS-HAP) co-substituted nanopowders. The nanopowders were tested against Escherichia-coli and Staphylococcus aureus bacterial strains. In addition, nanopowders were soaked in SBF to test their in-vitro bioactivity. Finally, products were also tested to deliver Ibuprofen drug under different pH environments. The dual ionic substitution conferred the nanopowders with appropriate properties suitable for multifunctional therapeutic applications, including tissue regeneration, antibacterial, and drug delivery applications.

The Physico-Chemical Properties and Exploratory Real-Time Cell Analysis of Hydroxyapatite Nanopowders Substituted with Ce, Mg, Sr, and Zn (0.5-5 at.%).

Cation-substituted hydroxyapatite (HA), standalone or as a composite (blended with polymers or metals), is currently regarded as a noteworthy candidate material for bone repair/regeneration either in the form of powders, porous scaffolds or coatings for endo-osseous dental and orthopaedic implants. As a response to the numerous contradictions reported in literature, this work presents, in one study, the physico-chemical properties and the cytocompatibility response of single cation-doped (Ce, Mg, Sr or Zn) HA nanopowders in a wide concentration range (0.5–5 at.%). The modification of composition, morphology, and structure was multiparametrically monitored via energy dispersive X-ray, X-ray photoelectron, Fourier-transform infrared and micro-Raman spectroscopy methods, as well as by transmission electron microscopy and X-ray diffraction. From a compositional point of view, Ce and Sr were well-incorporated in HA, while slight and pronounced deviations were observed for Mg and Zn, respectively. The change of the lattice parameters, crystallite size, and substituting cation occupation factors either in the Ca(I) or Ca(II) sites were further determined. Sr produced the most important HA structural changes. The in vitro biological performance was evaluated by the (i) determination of leached therapeutic cations (by inductively coupled plasma mass spectrometry) and (ii) assessment of cell behaviour by both conventional assays (e.g., proliferation—3-(4,5-dimethyl thiazol-2-yl) 5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay; cytotoxicity—lactate dehydrogenase release assay) and, for the first time, real-time cell analysis (RTCA). Three cell lines were employed: fibroblast, osteoblast, and endothelial. When monophasic, the substituted HA supported the cells’ viability and proliferation without signs of toxicity. The RTCA results indicate the excellent adherence of cells. The study strived to offer a perspective on the behaviour of Ce-, Mg-, Sr-, or Zn-substituted HAs and to deliver a well-encompassing viewpoint on their effects. This can be highly important for the future development of such bioceramics, paving the road toward the identification of candidates with highly promising therapeutic effects.

Preparation of Silicon Hydroxyapatite Nanopowders under Microwave-Assisted Hydrothermal Method.

The synthesis of partially substituted silicon hydroxyapatite (Si-HAp) nanopowders was systematically investigated via the microwave-assisted hydrothermal process. The experiments were conducted at 150 °C for 1 h using TMAS (C4H13NO5Si2) as a Si4+ precursor. To improve the Si4+ uptake in the hexagonal structure, the Si precursor was supplied above the stoichiometric molar ratio (0.2 M). The concentration of the TMAS aqueous solutions used varied between 0.3 and 1.8 M, corresponding to saturation levels of 1.5–9.0-fold. Rietveld refinement analyses indicated that Si incorporation occurred in the HAp lattice by replacing phosphate groups (PO43−) with the silicate (SiO4−) group. FT-IR and XPS analyses also confirmed the gradual uptake of SiO4− units in the HAp, as the saturation of Si4+ reached 1.8 M. TEM observations confirmed that Si-HAp agglomerates had a high crystallinity and are constituted by tiny rod-shaped particles with single-crystal habit. Furthermore, a reduction in the particle growth process took place by increasing the Si4+ excess content up to 1.8 M, and the excess of Si4+ triggered the fine rod-shaped particles self-assembly to form agglomerates. The agglomerate size that occurred with intermediate (0.99 mol%) and large (12.16 mol%) Si contents varied between 233.1 and 315.1 nm, respectively. The excess of Si in the hydrothermal medium might trigger the formation of the Si-HAp agglomerates prepared under fast kinetic reaction conditions assisted by the microwave heating. Consequently, the use of microwave heating-assisted hydrothermal conditions has delivered high processing efficiency to crystallize Si-HAp with a broad content of Si4+.

Speedy bioceramics: Rapid densification of tricalcium phosphate by ultrafast high-temperature sintering

Due to unique osteogenic properties, tricalcium phosphate (TCP) has gained relevance in the field of bone repair. The development of novel and rapid sintering routes is of particular interest since TCP undergoes to high-temperature phase transitions and is widely employed in osteoconductive coatings on thermally-sensitive metal substrates.In the present work, TCP bioceramics was innovatively obtained by Ultrafast High-temperature Sintering (UHS). Ca-deficient hydroxyapatite nano-powder produced by mechanochemical synthesis of mussel shell-derived calcium carbonate was used to prepare the green samples by uniaxial pressing. These were introduced within a graphite felt which was rapidly heated by an electrical current flow, reaching heating rates exceeding 1200 °C min−1. Dense (> 93%) ceramics were manufactured in less than 3 min using currents between 25 and 30 A. Both β and α-TCP were detected in the sintered components with proportions depending on the applied current. Preliminary tests confirmed that the artifacts do not possess cytotoxic effects and possess mechanical properties similar to conventionally sintered materials. The overall results prove the applicability of UHS to bioceramics paving the way to new rapid processing routes for biomedical components.

Methylene Blue Dye Adsorption from Wastewater Using Hydroxyapatite/Gold Nanocomposite: Kinetic and Thermodynamics Studies.

The present work demonstrates the development of hydroxyapatite (HA)/gold (Au) nanocomposites to increase the adsorption of methylene blue (MB) dye from the wastewater. HA nanopowder was prepared via a wet chemical precipitation method by means of Ca(OH)2 and H3PO4 as starting materials. The biosynthesis of gold nanoparticles (AuNPs) has been reported for the first time by using the plant extract of Acrocarpus fraxinifolius. Finally, the as-prepared HA nanopowder was mixed with an optimized AuNPs solution to produce HA/Au nanocomposite. The prepared HA/Au nanocomposite was studied by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) analysis. Adsorption studies were executed by batch experiments on the synthesized composite. The effect of the amount of adsorbent, pH, dye concentration and temperature was studied. Pseudo-first-order and pseudo-second-order models were used to fit the kinetic data and the kinetic modeling results reflected that the experimental data is perfectly matched with the pseudo-first-order kinetic model. The dye adsorbed waste materials have also been investigated against Pseudomonas aeruginosa, Micrococcus luteus, and Staphylococcus aureus bacteria by the agar well diffusion method. The inhibition zones of dye adsorbed samples are more or less the same as compared to as-prepared samples. The results so obtained indicates the suitability of the synthesized sample to be exploited as an adsorbent for effective treatment of MB dye from wastewater and dye adsorbed waste as an effective antibacterial agent from an economic point of view.

Hydrothermal synthesis of hydroxyapatite powders using Response Surface Methodology (RSM).

Hydroxyapatite (HAp)—[Ca10 (PO4)6(OH) 2] has a similar chemical composition to bone material, making it the main mineral supplement in bone-making. Due to its high biocompatibility, hydroxyapatite is widely used in the repair of bone deficiencies and in the production of dental or orthopedic implants. In this research, hydroxyapatite nanopowder was synthesized using a hydrothermal technique. Fourier Transform Infrared Spectroscopy (FTIR) and transmission electron microscopy (TEM) were used to investigate the chemical structure and morphology of the synthesized hydroxyapatite powder. X-ray diffraction (XRD) was used to evaluate the phase analysis of HAp nanopowder. In addition, bioactivity HAp assessment was conducted by scanning electron microscopy (SEM) attached with Energy Dispersive X-Ray Spectroscopy (EDX) analysis. Response Surface Methodology (RSM) with central composite design (CCD) was used in order to determine the optimal conditions for yield, size, and crystallinity. Three independent variables (pH, temperature, and hydrothermal treatment time) were investigated. The yield was observed to increase in alkaline conditions; pH showed the greatest influence on the yield, size, and crystallinity of the synthesized hydroxyapatite, based on Analysis of Variance. The results of bioactivity evaluation are showed high bioactivity due to the formation of apatite on the surface of the synthesized nanopowder.

Hydroxyapatite nanophases augmented with selenium and manganese ions for bone regeneration: Physiochemical, microstructural and biological characterization

Hydroxyapatite (HAP) nanopowders with different manganese (Mn) and selenium (Se) contents with Mn/Ca and Se/P molar ratio of 1 mol%, 2.5 mol% and 5 mol% were synthesized by wet-co-chemical precipitation method. The results revealed that with either Mn or Se doping, ion-substituted apatite phase was achieved with good crystallographic features. The combined evidence obtained from spectrometric techniques revealed that nanocrystalline HAP was effectively doped with Mn and Se ions, where Se in form of SeO32− replaced PO43− and Mn2+ replaced Ca2+. Mn and Se doped HAP samples exhibited rod-like and needle-like morphology with strong tendency to form agglomerates. HAP enriched with Mn and Se represented a strong antibacterial effect and also showed prominent blood compatibility. From the biocompatibility testing, it was evident that Mn and Se doped HAP augmented the osteoblasts adhesion, migration and proliferation in a dose-dependent manner. To conclude from this study, it is clearly evident that the doping amount of both Mn and Se ions can determine the size and morphology of the final HAP product. Therefore, Mn and Se HAP nanopowders with molar ratio less than 5 mol% without any heat treatment can provide good crystallographic features to HAP with satisfying micro-structural, thermal and biological properties.

Evaluation of cell compatibility of surfaces patterned with hydroxyapatite nanopowders on Ti surfaces

Hydroxyapatite (HA) is a widely used biomaterial for coatings on prostheses, which is used to repair, replace and restore the function of traumatized or diseased bone. In the present study, template-assisted electrohydrodynamic atomization (TAEA) was used to pattern Ti surfaces (convex, concave and flat) with different HA nanoparticles, in order to evaluate the cellular responses. A comparison of biocompatibility between surfaces coated with locally prepared (SL) and commercially available HA nanopowders was carried out. The cytotoxicity and cellular responses to these substrates (i.e., cell adhesion, morphology and proliferation) were evaluated using human osteoblast-like cells (HOS) in vitro. The results demonstrate that Ti surfaces coated with HA (SL) and commercial HA supported HOS cell attachment and proliferation without eliciting any deleterious substances. Moreover, retention of cell viability and morphology of osteoblast-like cells were observed once cells were in contact with the surfaces and were comparable to that of the tissue culture control. Interestingly, cells attached to HA (SL) elicited a better response. Proliferation of cells on convex surfaces was relatively higher in comparison to that of the concave and flat surfaces, which could be due to increased surface area of the HA (SL).

Synthesis, characterization, bactericidal activity, and mechanical properties of hydroxyapatite nano powders impregnated with silver and zinc oxide nanoparticles (Ag-ZnO-Hap)

Hydroxyapatite (Hap) doped or embedded with silver has shown improved bactericidal properties, and its mechanical properties were greatly improved by doping or impregnating Hap with metals such as Magnesium or Zinc, or by impregnating Hap with metal oxides such as MgO, or ZnO. This work describes the preparation of Ag-ZnO-Hap nanocomposites with 4 different Ag-ZnO–Ca mole ratios. XRD, FTIR, SEM, and TEM analysis of all prepared materials identified Hap as the only crystalline phase present in all samples exhibiting a uniform rod-like morphology with particles in the 20–40 nm size range. Microwave Plasma-Atomic Emission Spectroscopy confirmed the presence of zinc and silver in all embedded Hap samples. The antibacterial activity was tested against two different strains; Escherichia coli (E. coli (MV10Nal), and Gram-negative Aggregatibacter actinomycetemcomitans (A.a). The mechanical testing consisted of evaluating breaking force, work of fracture, and brittleness/ductility of Hap and Ag/ZnO/Hap composites. Our study clearly shows that reinforcing Hap with silver and zinc oxide yields superior bactericidal and mechanical properties.

Novel yellow light emission from vanadyl ions-doped calcium-lithium hydroxyapatite nanopowders: structural, optical, and photoluminescence properties

Phosphor luminescent materials, especially those activated with transition metal ions, have been extensively investigated during the last decade because of their potential in various applications such as displays, medical imaging, lighting, and fluorescent lamps. In this study, a mechanochemical approach was used for the synthesis of novel yellow light-emitting vanadyl ion (VO2+)-doped calcium-lithium hydroxyapatite (CLHA) nanophosphors. The structural, morphological, optical, photoluminescence, and chromaticity properties of the as-prepared nanopowders were systematically examined. Phase structural analysis showed that the as-prepared samples were highly crystalline and corresponded to the hexagonal crystal phase of hydroxyapatite. X-ray photoelectron spectroscopy investigation indicated the existence of elements. The spectroscopic results indicate that the doped VO2+ ions belong to the tetragonally distorted octahedral site symmetry. The chromaticity results show that the chromaticity coordinates (x, y) for the VO2+-doped CLHA nanopowders were (0.448, 0.401), (0.430, 0.384), and (0.423, 0.377). The emission colors are positioned in the orange, orange-yellow, and pale-yellow regions, respectively, for VO2+-doped CLHA nanopowders. Thus, the light emission properties shift from orange to yellow as the dopant concentration increases from 0.01 to 0.05 mol%. These results demonstrate that phosphor materials doped with transition metal ions are suitable for display device applications.

Mesoporous Iron(III)-Doped Hydroxyapatite Nanopowders Obtained via Iron Oxalate

Mesoporous hydroxyapatite (HA) and iron(III)-doped HA (Fe-HA) are attractive materials for biomedical, catalytic, and environmental applications. In the present study, the nanopowders of HA and Fe-HA with a specific surface area up to 194.5 m2/g were synthesized by a simple precipitation route using iron oxalate as a source of Fe3+ cations. The influence of Fe3+ amount on the phase composition, powders morphology, Brunauer–Emmett–Teller (BET) specific surface area (S), and pore size distribution were investigated, as well as electron paramagnetic resonance and Mössbauer spectroscopy analysis were performed. According to obtained data, the Fe3+ ions were incorporated in the HA lattice, and also amorphous Fe oxides were formed contributed to the gradual increase in the S and pore volume of the powders. The Density Functional Theory calculations supported these findings and revealed Fe3+ inclusion in the crystalline region with the hybridization among Fe-3d and O-2p orbitals and a partly covalent bond formation, whilst the inclusion of Fe oxides assumed crystallinity damage and rather occurred in amorphous regions of HA nanomaterial. In vitro tests based on the MG-63 cell line demonstrated that the introduction of Fe3+ does not cause cytotoxicity and led to the enhanced cytocompatibility of HA.

Mechanical alloying and characterization of chlorine doped hydroxyapatite nanopowders

Chlorine-doped Hydroxyapatite (ClHA)(Ca10(PO4)6(OH)2-xClx) nanopowders were successfully synthesized using high planetary ball mill. Milling was carried from 1 to 8 h in order to study the effect of milling time on the doped powders. Additionally, a study on the effect of chlorine addition to HA was also done. XRD results confirmed that all the milled powders consisted apatite as main phase. A significant increase in the unit cell parameters of ClHA nanopowders was observed in contrast to pure HA. However, in doped powders the size decreased with an increase in milling time with a minimal change in the lattice parameters. Microscopic observations also revealed an overall increase in the particle size due to Cl− addition. FTIR results confirmed the incorporation of Cl ions into HA lattice. Hemocompatibility of the synthesized powders (pure HA and ClHA8) was investigated using bovine blood. It was seen that hemolysis ratios for both the samples were below 2%, indicating that the synthesized powders of HA and ClHA are hemocompatible and can be used in various biomedical applications.

Comparative Evaluation of Antibacterial Effects of Nanoparticle-Incorporated Orthodontic Primer: An In Vitro Study

Aim and Objectives: To compare and evaluate the antibacterial efficacy of various nanoparticles incorporated in orthodontic primer with that of conventional antimicrobial agents at different concentrations on Streptococcus mutans ( S. mutans) strain. Materials and Methods: Transbond XT Primer was mixed with 2.5% and 5% benzalkonium chloride (BAC), 0.2% and 2.5% chlorhexidine, 1% and 3% titanium dioxide (TiO2) nanoparticles, 0.2% and 0.5% nanohydroxyapatite, and 0.2% and 0.5% silica-doped nanohydroxyapatite powders. Antibacterial activity against S. mutans for all the materials was evaluated by the disk diffusion method for periods of 48 (T1) and 72 (T2) hours. Results: There was a significant increase in the antimicrobial activity of the orthodontic primer modified by the addition of antibacterial agents. The highest zone of inhibition against S. mutans was observed for silica-doped nanohydroxyapatite of 0.5% (11.03 mm) among all the nanoparticles, which was similar to the conventional antibacterial agents used in our study. Conclusions: • Among all the groups, BAC at 5% concentration showed the highest antimicrobial activity, and the least activity was exhibited by 1% TiO2 nanoparticles. • Silica-doped nanohydroxyapatite at 0.5% expressed the greatest antibacterial activity among all the nanoparticles. • All the materials showed sustained antibacterial activity even after 72 hours.

Synthesis and Characterization of Nano Hydroxyapatite from Waste Egg Shells for Orthopedic and Dental Applications

Hydroxyapatite (HAp) is a type of material that is widely used in orthopedic and dentistry as a bio-coating of implants for improvement in its osteointegration with bone tissue. HAp was processed and synthesized by a precipitation technique by utilizing a biological means eggshell. The synthesis technique involved the calcination of eggshell powder to obtain calcium oxide and then its titration at a controlled flow rate with phosphoric acid. Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray diffraction (XRD) investigations were carried out to confirm the formation of HAp. Whereas, the Scanning Electron Microscopy (SEM) demonstrated the shape and structure of the as-synthesized nanohydroxyapatite powder. The obtained results correlate with the literature. It was observed that the HAp formed was highly crystalline and all the peaks corresponded with HAp based on the standard XRD pattern of HAp (JCDPS card no. 09-432). It was clear from the small peaks that some Tri-Calcium Phosphate was also formed along with the hydroxyapatite. Very less crystallinity can be seen in the SEM micrograph of the eggshell. The nHAp formed was subjected to thermal treatment in a controlled environment. The thermal treatment resulted in improved crystallinity and refined grain size. It is noted that higher surface area biogenic HAp with highly interconnected nanoparticles will be useful in bone morphogenesis during bone surgery.

Quenching of the Eu3+ Luminescence by Cu2+ Ions in the Nanosized Hydroxyapatite Designed for Future Bio-Detection.

The hydroxyapatite nanopowders of the Eu3+-doped, Cu2+-doped, and Eu3+/Cu2+-co-doped Ca10(PO4)6(OH)2 were prepared by a microwave-assisted hydrothermal method. The structural and morphological properties of the products were investigated by X-ray powder diffraction (XRD), transmission electron microscopy techniques (TEM), and infrared spectroscopy (FT-IR). The average crystal size and the unit cell parameters were calculated by a Rietveld refinement tool. The absorption, emission excitation, emission, and luminescence decay time were recorded and studied in detail. The 5D0 → 7F2 transition is the most intense transition. The Eu3+ ions occupied two independent crystallographic sites in these materials exhibited in emission spectra: one Ca(1) site with C3 symmetry and one Ca(2) sites with Cs symmetry. The Eu3+ emission is strongly quenched by Cu2+ ions, and the luminescence decay time is much shorter in the case of Eu3+/Cu2+ co-doped materials than in Eu3+-doped materials. The luminescence quenching mechanism as well as the schematic energy level diagram showing the Eu3+ emission quenching mechanism using Cu2+ ions are proposed. The electron paramagnetic resonance (EPR) technique revealed the existence of at least two different coordination environments for copper(II) ion.

The effect of micro and nano hydroxyapatite powder on biocompatibility and surface integrity of Ti6Al4V (ELI) in powder mixed electrical discharge machining

The problem of achieving functional surface is receiving substantial attention with the demand for efficient medical devices in biomedical industry. To satisfy both mechanical and biomedical concerns, researchers try to develop appropriate commercial machining techniques. This study analyzes the micro and nano Hydroxyapatite (HAp) powder size effect on surface topography and biocompatibility of Ti-6Al-4V (ELI) biomaterial in Electrical Discharge Machining (EDM). We compare thoroughly the titanium surfaces that EDM’ed with three different HAp powder concentrations in Deionized Water (DW) (0 g l−1, 20 g l−1 Micro HAp, 20 g l−1 Nano HAp) and three pulse current levels (7 A, 12 A, 22 A). The roughness of surfaces varies between 0.38 μm and 6.61 μm. Using micro HAp powder in dielectric liquid lowered the surface roughness and enhanced the wettability whereas the nano HAp effect could be negligible. The Energy Dispersive x-ray Spectrometer results show the Ca and P ion migration from the HAp mixed dielectric to the workpiece surface during EDM. The x-ray Diffraction results affirmed the existence of HAp compounds and oxide phases in the surface structure. Biocompatibility tests employing MG63 osteoblast-like cells revealed that for 24 h culture period all EDM samples showed higher viability than the control in vitro. According to the statistical analyses ANOVA (Tukey), the MTT viability results showed a significant difference especially for those machined in micro HAp mixed DW dielectrics. On the other hand, for 72 h culture period, samples machined in DW with 7 and 12 A currents are more biocompatible and have a proliferative effect on MG63 cells. In conclusion, however the dependency on pulse current, powder additive, and topography of the surface exist; EDM can be employed as an effectual treatment to enhance the biocompatibility.

Structural, photoluminescence, antibacterial and biocompatibility features of zinc incorporated hydroxyapatite nanocomposites

The development of bone-implant materials with enhanced bioactivity and biocompatibility has become important in the field of orthopedics. This preparation of nanocomposites of pure Hydroxyapatite (HAp) nanopowder, Hydroxyapatite-Zinc (HAp-Zn), Hydroxyapatite-reduced Graphene oxide (HAp-rGO) and Hydroxyapatite-Zinc-reduced Graphene Oxide (Hap-Zn-rGO) were accomplished using the sol–gel method. The effect of Zn and rGO on the structural, morphological, optical, antimicrobial property and biocompatibility of hydroxyapatite nanopowders are studied. The structural characterization analysed through XRD. The pure HAp and HAp-rGO exhibited hexagonal structure and incorporation of Zn in the host lattice changed this structure into orthorhombic. The average crystallite size ranges from 37 to 51 nm for various nanocomposites. The incorporation of rGO and Zn ions decreased the overall crystallite size. The presence of functional groups in the samples is analyzed and confirmed using FTIR analysis. The SEM photos revealed the structures and morphology of the nanoparticles. The chemical compositions are investigated using Energy Dispersive X-ray analysis (EDX), and all the ratios are in good agreement with the stoichiometry ratio. The photoluminescence emission peaks received around 468 nm and 385 nm and the reasons are discussed in terms of oxygen vacancies and some electronic transition between states. The optical band gap values were redshifted due to the incorporation of rGO with HAp. The in vitro antibacterial activities and biocompatibility of the synthesized pure hydroxyapatite and HAp-Zn-rGO nanocomposite are investigated using Kirby-Bauer antibacterial testing and MTT assay, respectively. The results show that zinc incorporated hydroxyapatite nanocomposites are more toxic against all bacterial strains and did not show any toxicity against living tissues.