Hydroxyapatite Nanoplates Research Articles

Nano-hydroxyapatite filled EPDM nanocomposite: towards green elastomeric thermal insulating coating with superior mechanical, thermal, and ablation properties

ABSTRACT Heat-shielding composite materials containing asbestos has been used for thermal insulation of aerospace rocket motors. However, asbestos has carcinogenic effects on both human and environment. This study was directed to the development of novel elastomeric nanocomposite thermal-shielding coating (asbestos-free); the developed elastomeric nanocomposite was based on hydroxyapatite (HA) nanoparticles (NPs) in an ethylene propylene diene monomer (EPDM) matrix. HA is a bio-ceramic material with 18.5 wt % phosphorus; HA can act as nano phosphorus-based fire extinguisher. HA NPs were synthesized by continuous hydrothermal technique; high crystalline HA nanoplates of 350 nm length, and 100 nm width were successfully developed. HA NPs were integrated into EPDM matrix; uniform dispersion of HA particles was verified via EDAX analysis. The impact of HA NPs on EPDM tensile strength, elongation-at-break, hardness, density, thermogravimetric analysis (TGA), thermal conductivity test, and ablation test was assessed to asbestos fibers. HA/EPDM secured superior mechanical properties compared with Asbestos/EPDM; HA NPs secured an increase the tensile strength, elongation at break by 16.2% and 105.3% respectively. HA with surface hydroxyl groups could be integrated into EPDM matrix via chemical bonding. HA offered novel thermal shielding properties; HA secured a decrease in thermal conductivity coefficient by −21.1%; and the best ablation resistance was increased by + 31.5%. Residual weight was increased by 13%, compared with asbestos fibers.

New highly efficient 2D/1D HAp/g‒C3N4 photocatalyst thin film insight into crystal orientation and C‒vacancy effects.

The novel synthetic Sol‒EPD process of a thin film including of well decorated g‒C3N4 nanotubes on plate‒like hydroxyapatite (HAp) were applied. Using Sol‒EPD designable method anisotropic growth of HAp nanocrystals on the substrate were achieved. It has provided the orientation of the different crystal facets resulted in the photogenerated O‒vacancy from phosphate groups. Based on the studied XRD pattern, EPD deposited film of HAp was oriented along c‒plane that can improve the photocatalytic activity of the designed composited film. Systematic designing was applied for decoration of g‒C3N4 nanotubes on the HAp under thermal condensation of melamine coincide with calcination of HAp. This new designed HAp/g‒C3N4 nanofilm was shown high photocatalytic efficiency and completely degradation of persistent pollutant of 4‒nitrophenol in the aqueous solution. According to the electrochemical impedance spectroscopy and current density studies, the higher charge separation/low charge recombination results were obtained for composited g‒C3N4/HAp nano‒film comparing with the single films of HAp and urchin like g‒C3N4. This high separation of charge pairs should be also assigned to the special designed morphology. In addition, wrapped like structure of g‒C3N4 nanotubes with C‒vacancy around HAp nanoplates play key role in separation of photo‒induced charge pairs, light diffusion, and high light harvesting within hollow nanotube. It can be highlighted that the composite degraded more than 95% of 4‒nitrophenol during 90min that after 5 runs the photocatalytic activity was not significantly changed.

Synergism of nanothermite and nanophosphrous compound for advanced infrared flares with superior spectral performance

ABSTRACT Hydroxyapatite (HA) is one of the most common biocompatible material with high phosphorous content (18.5 wt %). HA is thermally stable compound that requires high temperature to decompose; upon decomposition active phosphorus can offer enhanced thermal signature for effective countermeasure of infrared missiles. High reaction temperature can be accomplished via high energy density materials such as nanothermites. This study reports on the facile synthesis of Fe2O3 nanoparticles (5 nm average particle size) and HA nanoplates (530 nm length, 140 nm width) using hydrothermal synthesis. Whereas ferric oxide was employed for nanothermite reactions, HA was employed as phosphorous source material. The effect of developed nanomaterials on thermal signature of traditional Magnesium/Teflon/Viton (MTV) decoy flare was evaluated using Arc-Optics IR spectrometer (1–6 µm). Whereas Fe2O3 (8 wt %) offered enhanced average intensity value by 67%; synergism between HA and Fe2O3 particles offered enhanced spectral performance by 97%. Key radiometric performance parameter is the relative intensity ratio Ɵ(Ɵ = Iα/ Iβ); synergism between HA and Fe2O3 offered superior radiometric performance with Ɵ value of 0.59; this value is similar to aircraft value. This novel spectral performance shaded the light on HA as novel phosphorus material for advanced infrared countermeasure flares.

Intrinsic effect of anionic surfactant on the morphology of hydroxyapatite nanoparticles and its structural and biological properties

This paper describes the potential effect of anionic surfactant on the morphology of hydroxyapatite (HA) nanostructures during hydrothermal synthesis. Sodium dodecyl sulfate (SDS) was used as an anionic surfactant. Various concentrations of SDS were used to study morphological changes in HA due to the presence of the surfactant. The final morphology, after treatment by a hydrothermal method, revealed that the anionic surfactant induced growth in one direction (a-axis) and inhibited growth in the other (c-axis) based on the charge distribution on the crystal faces of HA. Further structural analysis (by X-ray diffraction) confirmed this growth along the a-axis. In-vitro cellular analysis revealed that the plate-like nanoparticles possess better bioactivity than their bulk counterparts. Therefore, HA nanoplates could be used for applications that include controlled drug delivery and bone mineralization.

Novel Thermoset Nanocomposite Intumescent Coating Based on Hydroxyapatite Nanoplates for Fireproofing of Steel Structures

Thermoset nanocomposite intumescent coating swells under the influence of heat forming a thick cohesive insulating barrier; it is one of the most effective ways for fire protection of steel structures. This study reports on the sustainable fabrication of hydroxyapatite (HA) nanoplates as an efficient phosphorous-based flame retardant agent (phosphorous content of 18.5 wt%). Epoxy nanocomposite, based on the synergism between HA particles and advanced intumescent flame retardant agent (commercially known as AP750) was developed. This novel nanocomposite was able to resist a direct flame source at 1700 °C and to self extinguish; it demonstrated an enhanced flammability performance in cone calorimetry with 51% decrease in the peak heat released. Nanocomposite layer of 3 mm thickness was employed for steel substrate protection against direct heat source. The developed intumescent coating was able to protect the steel substrate from heat source at 900 °C. It offered an improved performance, in terms of the coating’s mechanical barrier, and flame resistance properties. HA nanoplates could propose a gas phase effect due to the release of active flame scavengers such as $$ {\text{PO}}_{2}^{ \cdot } $$, PO·, and HPO·. Furthermore, HA could expose a condensed phase effect via the formation of a protective charr layer.

New insights into nanostructure and geochemistry of bioapatite in REE-rich deep-sea sediments: LA-ICP-MS, TEM, and Z-contrast imaging studies

Rare earth elements (REE) and yttrium (Y), termed as REY, are recently found to be extremely enriched in some pelagic sediments, which could be an important resource for REY in the future. However, their enrichment mechanism remains controversial. Because biogenetic apatite is one of the most important REY carriers in REY-rich deep-sea sediment, it is critical to identify its mineralogical and geochemical characteristics by using combined methods of in situ chemical analysis and atomic resolution chemical imaging.Scanning electron microscope and transmission electron microscopy studies reveal that bioapatite fossils mainly consist of aligned hydroxyapatite nano-plates. Laser ablation-inductively coupled plasma-mass spectrometry analyses show that the REY are not uniformly distributed within the studied bioapatite fossils. Concentration profiles from the measurements and modeling analyses indicate that the major REY should be incorporated into the bioapatite fossil from seawater as well as the pore water during the early stage of diagenesis. Z-contrast imaging results reveal the following two possible coupled substitutions in the apatite: REE3+ + Na+ ↔ 2Ca2+ and/or REE3+ + Si4+ ↔ Ca2+ + P5+, which is distinguished from those ion-absorption-type REE deposits on land. Our study indicates that bioapatite fossils are prone to undergo alteration during diagenesis, and thus cautious examination should be taken when applying REE signal of bioapatite as a proxy for palaeo-ocean environmental reconstruction.

Template-oriented synthesis of hydroxyapatite nanoplates for 3D bone printing.

The design of hydroxyapatite (HA) nanoarchitecture is critical for fabricating artificial bone tissues as it dictates the biochemical and the mechanical properties of the final product. Herein, we incorporated a simple hard-template approach to synthesise single crystal nanoplates of HA. We used the 2D graphitic nitride (g-C3N4) material to prepare an HA sol-gel under hydrothermal conditions. A new HA nanostructure was then formed during the calcination and removal of g-C3N4 at a higher temperature, which finally led to the production of nanoplates (thickness of ∼100 nm) while in lateral dimension the average size was in the micrometre scale. We characterised the synthesised HA nanoplates with XRD, TEM, and HRTEM. The theoretically predicted nanostructure construction based on Wulff's method is in full agreement with the experimental observations. We then prepared different weight ratios of HA and polylactic acid (PLA) composites for artificial 3D bone fabrication. The strong interaction between PLA and HA's (110) facet, which was the second most prevalent, resulted in the composite's mechanical robustness. After mechanical testing, an optimum ratio was selected for biological studies and 3D printing. Biological experiments demonstrated that the synthesised composite had excellent viability in vitro.

Monoclinic Hydroxyapatite Nanoplates Hybrid Composite with Improved Compressive Strength, and Porosity for Bone Defect Repair: Biomimetic Synthesis and Characterization.

Calcium phosphate cement (CPC) has been used for bone restoration despite its intrinsic fragile property. In order to enhance the CPC mechanical properties, biopolymers were introduced as filler to prepare CPC based cements. Chitosan/tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA) based cement for bone repair has been prepared in the study. Solidification of the prepared cement was carried out in a simulate body fluid at 37 degrees C. The introduction of chitosan improved the mechanical performance of the as-prepared CPC hybrid nanocomposite. FTIR, SEM, TEM, HRTEM, XRD, and SAED were used to characterize the CPC nanocomposite. Data simulations have been performed to assist in determining the crystalline phase/s in the CPC hybrid nanocomposite. Based on the SAED, HRTEM measurements and data simulations, a monoclinic phase of hydroxyapatite (HAP) with a plate-like structure was obtained in the CPC system, which is believed to be responsible for the observed enhancement in CPC mechanical properties. The obtained composite has a biocompatibility comparable to that of commercial sample.

A novel in situ deposition of hydroxyapatite nanoplates using anodization/hydrothermal process onto magnesium alloy surface towards third generation biomaterials

Third-generation biomaterials aim to stimulate specific cellular responses at the molecular level, these materials characterized with a resorbable and bioactivity that help body heal once they have been implanted. Here, a biomimetic method was used to generate hydroxyapatite (HA) nanoplates on the surface of AZ31B Mg alloy via anodization in simulated body fluid (SBF), followed by a hydrothermal (HT) process. The resulting nanoplates were characterized using FE-SEM, XRD, and FT-IR, surface hydrophobicity, in addition, corrosion was assessed electrochemically. The excellent bioactivity of the treated samples compared with naked ones were confirmed in vitro with MC3T3-E1 osteoblastic cells with significant growth and proliferation.

The ionic liquid assisted green synthesis of hydroxyapatite nanoplates by Moringa oleifera flower extract: A biomimetic approach

This report deals an attempt for a successful green synthesis of hydroxyapatite nanoplates assisted from Moringa oleifera flower extract and 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The prepared nanoplates were calcinated at two different temperatures and the crystallinity, particles size and morphology were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) techniques. These results proved the crystal growth nucleation of HAp nanoplates at different calcination temperatures. FTIR results were established the interaction of ion precursors with polyphenolic hydroxyl groups from flower extract. The important role of ionic liquid assessment also confirmed the formation of amorphous into crystalline plate like structures.

Bioinspired synthesis of hydroxyapatite nanocrystals in the presence of collagen and l-arginine: Candidates for bone regeneration.

This work aims at the bioinspired synthesis of hydroxyapatite (HAp) crystals in the presence of both collagen and l-arginine, in an effort to obtain a homogeneous hybrid material, having a bone-like nanostructure. Collagen (Col) is the most commonly utilized protein in most species of life, while L-arginine (Arg) encourages cell attachment, proliferation, and differentiation on HAp surfaces. Transmission electron microscopy, X-ray diffraction and Fourier transform-infrared spectroscopy were used to analyze surface morphology and structure of nanocrystals obtained under different synthesis conditions. It was shown that collagen and arginine content affect HAp crystallization. Collagen has an inhibition effect since HAp crystal size is reduced with the increase of collagen content. The presence of arginine is crucial as a critical content exists (Ca(2+):Arg = 1:1) under which HAp nanocrystals coexist with brushite. Under the optimum synthesis conditions (HAp/Col weight ratio 70/30 and Ca(2+):Arg molar ratio 1:1) HAp nanoplates of a uniform size (around 10 × 10 nm) were obtained. The biocompatibility of this hybrid powder was assessed using human bone marrow derived mesenchymal stem cells (MSCs). Cell response in terms of MSC attachment (scanning electron microscopy) and viability/proliferation (Alamar Blue) demonstrated a noncytotoxic effect of the new material.

Controlled template synthesis of lamellar hydroxyapatite nanoplates as a potential carrier for gene delivery

Lamellar hydroxyapatite (L-HAp) nanoplates of varying structure and morphology were synthesized by changing the template synthesis conditions including content of template agent and calcium and phosphate precursors. The as-prepared L-HAp nanoplates were characterized by XRD, TEM, and zeta potential analyses and their cytoxicity, DNA loading capacity, and gene transfection efficiency were evaluated. Results showed that loading of template agent and concentration of precursors had significant effects on the structure and morphology of L-HAp nanoplates. The L-HAp nanoplates with good lamellar structure could allow the intercalation of DNA molecules into the gallery of L-HAp and thus exhibited higher DNA loading capacity and transfection efficiency. It has been demonstrated that the structure and morphology of L-HAp nanoplates can be controlled by adjusting processing variables and that the L-HAp nanoplates with good lamellar structure has great potential as a gene delivery vector in non-viral based therapy.

Continuous synthesis of dispersant-coated hydroxyapatite plates

A continuous flow hydrothermal synthetic route which allows the direct “in situ” capping/coating of hydroxyapatite nanoplates with functional dispersants in a single stage is reported.

Hydroxyapatite-TiO(2)-based nanocomposites synthesized in supercritical CO(2) for bone tissue engineering: physical and mechanical properties.

Calcium phosphate-based nanocomposites offer a unique solution toward producing scaffolds for orthopedic and dental implants. However, despite attractive bioactivity and biocompatibility, hydroxyapatite (HAp) has been limited in heavy load-bearing applications due to its intrinsically low mechanical strength. In this work, to improve the mechanical properties of HAp, we grew HAp nanoplates from the surface of one-dimensional titania nanorod structures by combining a coprecipitation and sol-gel methodology using supercritical fluid processing with carbon dioxide (scCO2). The effects of metal alkoxide concentration (1.1-1.5 mol/L), reaction temperature (60-80 °C), and pressure (6000-8000 psi) on the morphology, crystallinity, and surface area of the resulting nanostructured composites were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and Brunauer-Emmet-Teller (BET) method. Chemical composition of the products was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge structure (XANES) analyses. HAp nanoplates and HAp-TiO2 nanocomposites were homogeneously mixed within poly(ε-caprolactone) (PCL) to develop scaffolds with enhanced physical and mechanical properties for bone regeneration. Mechanical behavior analysis demonstrated that the Young's and flexural moduli of the PCL/HAp-TiO2 composites were substantially higher than the PCL/HAp composites. Therefore, this new synthesis methodology in scCO2 holds promise for bone tissue engineering with improved mechanical properties.

Novel bone regeneration matrix for next-generation biomaterial using a vertical array of carbonated hydroxyapatite nanoplates coated onto electrospun nylon 6 nanofibers

For the first time, a novel method for nucleation and deposition of vertically arrayed carbonated hydroxyapatite (HA) nanoplates without obvious agglomeration onto the post-electrospun nylon 6 (N6) nanofibers was successfully designed. The technique is based on a simple hydrothermal treatment of the fabricated N6 mat. The excellent bioactivity of the treated scaffold was confirmed in vitro within MC3T3-E1 osteoblastic cells by significant attachment and in-growth activity on the treated scaffold, and the ability to differentiate into osteoblastic cells with excellent osteogenic potential higher than that of plain nanofibers. Based on this study, the bioactive N6 nanofibers matrix treated with HA nanoplated is regarded as a promising next-generation biomaterial in the bone regeneration field.

Mg-doped hydroxyapatite nanoplates for biomedical applications: A surfactant assisted microwave synthesis and spectroscopic investigations

Nanoplates of Mg doped hydroxyapatite (Mg-HAp) were derived successfully and rapidly via microwave irradiation technique. Hydroxyapatite (HAp) is the hard tissues and main inorganic component in mammals. Different nanostructures of HAp exist in different parts of human bone but nanorods are very common due to its intrinsic nature to grow in rode-like structure under physiological as well as under applied ambient conditions in laboratory. On the addition of Mg at very low level (0.06mol%) in pure HAp results the formation of 2-D plate-like nanostructures rather than rod-like which is the matter of interest. In this attempt our efforts have been focused on the study of effect of Mg incorporation on structural and spectroscopic properties of HAp prepared via microwave irradiation technique. This technique is preferred due to several advantages viz. very fast as well as homogeneous heating, time/energy saving and eco-friendliness. The calcium nitrate tetrahydrate (Ca(NO3)2⋅4H2O)) as a source of calcium, magnesium nitrate hexahydrate (Mg(NO3)2⋅6H2O) as a source of magnesium, disodium hydrogen phosphate dihydrate (NaH2PO4⋅2H2O) as a source of phosphorous and sodium ethylene diamine tetra acetate (NaEDTA) as a surfactant were used as starting reagents. Sodium hydroxide (NaOH) pellets were employed to adjust the pH value of final solution. The solution of fixed pH value was kept into the microwave oven generating waves of frequency 2.45GHz (water absorption frequency) and power 750W for 8min. The precipitate thus obtained was washed, centrifuged and then dried at 100°C for 2h. Dried powder was then calcined at 700°C for 2h. The bright white powder thus obtained was characterized structurally using X-ray diffraction and SEM techniques and spectroscopically by FT-IR and Raman techniques. Structural and spectroscopic analysis revealed the formation of Mg doped HAp [Mg-HAp: (Ca4.94Mg0.06) (PO4)3OH], nanoplates having average crystallite size of 26nm as estimated by Scherrer’s formula.

Preparation and characterization of vertically arrayed hydroxyapatite nanoplates on electrospun nanofibers for bone tissue engineering

Abstract The aim of this study is to develop a facile and an efficient approach for providing the electrospun nanofibers scaffold with a vertically well-aligned and homogeneous distribution of hydroxyapatite (HA) nanoplates that coat the scaffold while maintaining its fibrous and porous structure. Crystal growth of HA nanoplates from a colloidal solution onto the surface of nylon (N6) nanofibers was carried out via a hydrothermal approach. The factors affecting the scaffold’s morphology, macrostructure and the interfacial bonding between the constituents as well as the influence of crystal size were characterized and well elucidated. The results revealed that the deposition of dense and thick uniform nanoplates was perpendicular and nucleated in a parallel configuration onto the longitudinal axes of the individual nanofibers during the treatment process. The sizes of the nanoplates, which are strongly dependent on the reaction time, were 30 and 95 nm in length, with thicknesses of 17–19 nm, after 2 and 3 h respectively. The nanoplates improve the mechanical properties of the HA/N6 biocomposite scaffolds. The surface properties of the fabricated scaffolds appeared to have a greater effect on the early stages of osteoblast behavior (cell attachment and proliferation). The cells attached, grew and proliferated faster on culture-coated scaffolds in comparison with the pristine ones. Our results indicate that the treated scaffolds fulfill the basic requirements of bone tissue engineering scaffolds, and have the potential to be applied in orthopedic and reconstructive surgeries.

Hydrothermal fabrication of hydroxyapatite/chitosan/carbon porous scaffolds for bone tissue engineering

Porous carbon fiber felts (PCFFs) have great applications in orthopedic surgery because of the strong mechanical strength, low density, high stability, and porous structure, but they are biologically inert. To improve their biological properties, we developed, for the first time, the hydroxyapatite (HA)/chitosan/carbon porous scaffolds (HCCPs). HA/chitosan nanohybrid coatings have been fabricated on PCFFs according to the following stages: (i) deposition of chitosan/calcium phosphate precursors on PCFFs; and (ii) hydrothermal transformation of the calcium phosphate precursors in chitosan matrix into HA nanocrystals. The scanning electron microscopy images indicate that PCFFs are uniformly covered with elongated HA nanoplates and chitosan, and the macropores in PCFFs still remain. Interestingly, the calcium-deficient HA crystals exist as plate-like shapes with thickness of 10-18 nm, width of 30-40 nm, and length of 80-120 nm, which are similar to the biological apatite. The HA in HCCPs is similar to the mineral of natural bone in chemical composition, crystallinity, and morphology. As compared with PCFFs, HCCPs exhibit higher in vitro bioactivity and biocompatibility because of the presence of the HA/chitosan nanohybrid coatings. HCCPs not only promote the formation of bone-like apatite in simulated body fluid, but also improve the adhesion, spreading, and proliferation of human bone marrow stromal cells. Hence, HCCPs have great potentials as scaffold materials for bone tissue engineering and implantation.

Environmentally Friendly Synthesis of Hydroxyapatite Nanoplates and their Adsorption Behavior of Proteins

By a environmentally friendly method with the control of anionic amino acid surfactant N-lauroylsarcosine sodium (Sar-Na), hydroxyapatite (HAP) nanoplates were synthesized and the adsorption behavior of bovine serum albumin (BSA) were carefully studied. The products were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Results showed that hydroxyapatite nanocrystals with lengths of 100 nm, a width of 10 nm and a high aspect ratio (10:1) were obtained. Results of UV-Vis spectrum indicate that prepared hydroxyapatite nanoplates can be effectively adsorbed BSA. The current work provides a new approach to produce biomaterials.

Synthesis of Hydroxyapatite Nanoplates by the Hydrothermal Reaction Method with Anionic Amino Acid Surfactant

By hydrothermal reaction method with the control of anionic amino acid surfactant N-lauroylsarcosine sodium(Sar-Na),single crystal hydroxyapatite(HAP) nanoplates were synthesized and different synthetic conditions were carefully studied.The products were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and Fourier transform infrared(FTIR) spectroscopy.Results showed that hydroxyapatite nanocrystals with lengths of 0.5-1.0 μm,a width of 30 nm,and a high aspect ratio(20:1) were obtained.By increasing the concentration of N-lauroylsarcosine sodium,the morphology of the hydroxyapatite varied from oval to plate-like.These results show that N-lauroylsarcosine sodium can induce the formation of hydroxyapatite with different morphologies.The current work provides a new approach to tune the aspect ratio of hydroxyapatite nanoplates.