Sodium dodecyl sulfate mediated microwave synthesis of biocompatible superparamagnetic mesoporous hydroxyapatite nanoparticles using black Chlamys varia seashell as a calcium source for biomedical applications

Designing biocompatible superparamagnetic mesoporous nanoparticles for advanced healthcare applications has received much attention. In this research, we have synthesized intrinsic mesoporous superparamagnetic hydroxyapatite (HAp) nanoparticles using bio-waste of black Chlamys varia seashell as a calcium source by sodium dodecyl sulfate (SDS)–enabled microwave-assisted synthesis approach. The synthesized Fe-doped HAp nanoparticles were characterized using various characterization techniques to know the phase purity and morphological features. The incorporation of Fe greatly affected the morphology of HAp nanoparticles without affecting their crystalline phase. Superparamagnetic behavior was observed with the incorporation of Fe in the HAp nanoparticles. Further, saturation magnetization was enhanced with higher incorporation of Fe ions. The cytotoxicity studies of the synthesized pure and Fe-doped HAp samples conducted using a human osteoblasts cell line (MG63), which indicated that Fe-doped HAp nanoparticles are biocompatible. Further, antibacterial activity analysis also confirmed their excellent antibacterial performance against different pathogens. Hence, SDS-enabled microwave-assisted synthesis approach using seashell as a calcium source would be a better approach for the production of intrinsic mesoporous superparamagnetic HAp nanoparticles for various biomedical applications, such as drug targeting, hyperthermia cancer therapy, and magnetic resonance imaging.     

The Physical and Antimicrobial Properties of Silver Doped Hydroxyapatite Sintered by Microwave and Conventional Sintering

In this paper, the silver-doped hydroxyapatite (AgHAp) nanoparticles were successfully synthesized by conventional and microwave sintering. The structural and antibacterial properties of AgHAp without heat treatment (AgHAp-90) and after heat treated at 800 and 1000?°C by conventional (AgHAp-800CS, AgHAp-1000CS) and microwave sintering (AgHAp-800MS, AgHAp-1000MS) were discussed respectively. The results of X-ray diffraction and fourier transform infrared spectroscopy suggested that the pure phase of AgHAp nanoparticles were obtained at 800?°C, but the β-TCP phase was observed when the temperature up to 1000?°C. Scanning electron microscopy images showed that the morphology and size of the nanoparticles changed with the improvement of temperature. The energy dispersive X-ray analysis identified the existence of Ag, Ca, P. The antibacterial test of AgHAp showed the excellent antimicrobial activity against gram-negative strains Escherichia coli and gram-positive strains Staphylococcus aureus. Also, the results showed the AgHAp had a smaller effect on gram-positive strains compare with gram-negative strains, and the antimicrobial activity of particles sintered by microwave was better than samples sintered by conventional. It showed the great advantages of microwave sintering. The silver ion releasing in solution was measured by the inductively coupled plasma and elucidated the results of antibacterial tests.     

Influence of concentration of hydroxyapatite surface modifier agent on bioactive composite characteristics

The characterization of chitosan – hydroxyapatite (CH – HAp) composite sponges prepared via freeze-drying methodology is reported in this study. Stearic acid (SA), added as a surface modifier of the HAp nanoparticles, induced changes in the TG/DTG results, particle size distribution and particle morphology. Composite sponges prepared with SA coated HAp demonstrated enhanced biocompatibility and structural properties, as compared to the composites prepared with uncoated HAp. SA coating modified the morphology of the composite, promoting a better dispersion of HAp particles within the composite sponges, and better homogeneity of the polymeric cover with HAp particles. The viability of the composites for cell culture applications was analyzed, and the results suggest that the sponges are biocompatible. Therefore, SA proved to be a good candidate for surface coating of HAp nanoparticles prevent agglomerations, and could be used effectively in the preparation of biocompatible composite sponges with chitosan.     

Rapid microwave-assisted synthesis of gold loaded hydroxyapatite collagen nano-bio materials for drug delivery and tissue engineering application

A rapid microwave assisted facile synthetic technique was adopted to load gold nanoparticles (Au) on hydroxyapatite (HAp) surface. HAp nanoparticles were primarily synthesized by wet precipitation technique and further used for gold loading and successive collagen coating for biomedical applications. The microwave-assisted controlled synthesis technique with three heating cycles allows the very fast growing of Au seeds over HAp facets. Different sophisticated analytical techniques and spectroscopic characterization were employed to confirm the structural, chemical, and morphological features. The synthesized different concentration “Au” loaded hetero nanostructures coated with collagen (Au–HAp–Col) optimized for drug (Doxorubicin: DOX) loading and releasing purposes for biomedical applications. The maximum drug-loading efficiency of ~58.22% and a pH responsive releasing of ~53% (at pH 4.5) was obtained for 0.1?wt% Au–HAp–Col nanoparticles. To study the cytotoxic effects from the hetero nanostructures, MG-63 osteoblast-like cells were exposed to different concentration ranges on Au–HAp, Au–HAp–Col, and DOX loaded Au–HAp–Col nanoparticles. The non-toxic and bioactive properties of the synthesized nanoparticle-fabricated scaffold promotes cellular attachment, growth, and proliferation. These results indicated that optimized Au–HAp–Col nanoparticles may be promising drug delivery and scaffold materials for multifunctional biomedical applications.     

Synthesis of hydroxyapatite nanoparticles using surface carboxyl-functionalized carbon dots as template

Carbon dots (CDs), which are discrete, nearly spherical nanoparticles with sizes below 10?nm and large amounts of carboxylic acid moieties on the surface, have been proposed as an ideal template candidate for heterogeneous nucleators to regulate hydroxyapatite (HAp) nucleation and growth. In this paper, small HAp nanoparticles formed on carboxyl-functionalized CDs in situ were fabricated via the hydrothermal method. Investigation for the corresponding morphologies and detailed formation mechanisms of samples were conducted by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and Rietveld refinement. The optimum size and crystallinity of HAp particle had been obtained in the preparation when the additive content of CDs was 1.11?g/L. Moreover, results also suggested that CDs were served as nucleators in the HAp particles. Therefore, a novel synthetic strategy is presented for small HAp nanoparticles using CDs as template.     

Biomimetic fabrication of mulberry-like nano-hydroxyapatite with high specific surface area templated by dual-hydrophilic block copolymer

Novel porous and mulberry-like hydroxyapatite (HAp) nanoparticles with three-dimensionally hierarchical microstructures were developed by using the dual-hydrophilic block copolymer poly(methacrylate acid)-b-poly[N-(2-methacryloylxyethyl) pyrrolidone] (PMAA-b-PNMP) as the template. It was found that the morphology and Ca/P ratio of synthesized HAp was highly related to the concentration of block copolymer and solution pH, respectively. The morphological evolution of HAp nanoparticles in different conditions was investigated systematically by scanning electron microscopy (SEM), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The possible mechanism of PMAA-b-PNMP assisted mulberry-like HAp formation was also proposed based on the time-dependent TEM results. Attributing to the high specific surface area (SSA) of 119 m² g⁻¹, these mulberry-like HAp nanoparticles exhibited excellent adsorption ability for Congo Red (CR). The maximum adsorption capacity was 467 mg g⁻¹ according to the Langmuir monolayer adsorption model.     

Polyoxymethylene‐homopolymer/hydroxyapatite nanocomposites for biomedical applications

In this article, new polyoxymethylene (POM)/hydroxyapatite (HAp) nanocomposites for bone long‐term implants have been obtained and characterized by using FTIR, WAXD, SEM, TG, DSC, tensile tests, and in vitro evaluation. Characteristic bands both for extended chain crystals (ECC) and folded chain crystals (FCC) were observed in FTIR profiles for both pure POM and POM in POM/HAp nanocomposites. From WAXD analysis it has been found that the addition of HAp does not change the hexagonal system of POM in POM/HAp nanocomposites. Moreover, degree of crystallinity of POM increases with an increase of HAp content up to 1.0% and next decreases with an increase HAp content. It indicates that HAp nanoparticles up to 1.0% content act as effective nucleating sites. Mechanical tests revealed that Young's modulus increases, whereby, elongation at break and tensile strength decrease with increasing hydroxyapatite concentration. Results of in vitro investigations show that an increase of HAp content in POM nanocomposites facilitates formation of apatite layer on the sample surface and improves in vitro stability POM/HAp nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Milling media effects on synthesis,morphology and structural characteristics of single crystal hydroxyapatite nanoparticles

Abstract

This paper presents a dry mechanochemical process to produce hydroxyapatite (HAp) nanoparticles. Two distinct chemical reactions are introduced to prepare HAp powders using milling process. Structural and morphological properties of the obtained materials are studied by X-ray diffraction and transmission electron microscopy. The results reveal that the single crystal HAp nanoparticles have been successfully produced in metallic and polymeric vials through two different experimental procedures. Tempered chrome steel and polyamide-6 materials are adopted as the metallic and polymeric vials respectively. Nanoellipse, nanorod and nanosphere powders are obtained in these experimental procedures. Moreover, the obtained HAp powders through two distinct reactions exhibit average sizes about 12 and 15?nm using the tempered chrome steel vials, and about 16 and 17?nm using the polyamide-6 vials. The results indicate that single crystal HAp nanoparticles produced in polyamide-6 vials have suitable morphology and high production efficiency without any chemically stable contaminations.     

Synthesis of hydroxyapatite nanoparticles in ultrasonic precipitation

Nanocrystalline hydroxyapatite (HAp) was prepared by a precipitation method with aid of ultrasonic irradiation using Ca(NO₃)₂ and NH₄H₂PO₄ as source material and carbamide (NH₂CONH₂) as precipitator. The crystallization and morphology of the prepared nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanism and kinetics of the nano-hydroxyapatite were considered in particular, and the influence of the temperature and time on the HAp formation rate was also investigated. The results show that the needle-like HAp crystalline was prepared by the ultrasonic precipitation process. The HAp content increases with the preparation temperature and time. The adding of carbamide is helpful for formation of HAp nanoparticles. An Arrhenius relationship was found between the HAp formation rate and the temperature, and an apparent activation energy of 59.9 kJ/mol was obtained by calculation.     

Preparation and morphological investigation on bioactive ion-modified carbonated hydroxyapatite-biopolymer composite ceramics as coatings for orthopaedic implants

Bioactive ions (Mg, Sr, Zn) doped carbonated hydroxyapatite powders (dHAp) and pure carbonated hydroxyapatite (HAp) powders were prepared by wet chemical precipitation method. The bioactive ions were incorporated into the HAp matrix by co-precipitation from solution containing the appropriate amount of chloride salt of different ions. The morphology of pure HAp was mainly needle-like in nanometre size and the particles were disordered showing quasi-amorphous structure. The ion doping changed the morphology of particles, the dHAp particles had distorted spheroid shapes. Owing to the ion addition, the crystallinity of particles decreased. Particle aggregations can also be observed in both types of samples. HAp and dHAp loaded biopolymer polyvinylpyrrolidone (PVP) composite materials have also been developed by novel electrospinning technique. It has been shown that both the HAp and dHAp particles can be successfully incorporated into the PVP fibre web matrix and simultaneously the bioceramic powders were attached to the surface of polymer fibres. The surface of fibres was not fully covered with the particles. The ceramic powder addition to the polymer solution caused the polymer fibres to become more entangled and the diameters of fibres varied over a wider range compared to the base polymer fibres without bioceramic powder addition.     

Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

ABSTRACT: Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10-xAgx(PO4)6(OH)2 (x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp (x = 0) and Ag:HAp (x = 0.2). The Ag:Hap nanopowder showed higher inhibition.     

Size and morphology-controlled synthesis of mesoporous hydroxyapatite nanocrystals by microwave-assisted hydrothermal method

We report the rapid microwave-assisted hydrothermal synthesis of mesoporous hydroxyapatite (HAp) nanocrystals with controlled size, morphology, and surface area using various organic modifiers as regulators. The products were analyzed for their crystalline nature, phase purity, morphology, particle size and pore size distribution. Results indicated that ascorbic acid, cetyltrimethyl ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) play an important role to obtain needle like, rod like and fiber like mesoporous HAp nanocrystals with different specific surface area by controlling growth habit of HAp along c-axis. In addition, the prepared samples were B-type carbonated HAp similar to bone minerals. Therefore, the present approach can be a promising way to obtain precursor for making tissue engineering scaffolds, drug/protein delivery carriers and bone fillers with tunable characteristics.     

Calcium deficient hydroxyapatite by precipitation: Continuous process by vortex reactor and semi-batch synthesis

Precipitation of calcium deficient hydroxyapatite nanoparticles in an environmentally benign manner by using only dilute solutions of calcium hydroxide and phosphoric acid without pH adjustment and addition of other chemicals, and water, being the only by-product was investigated by using continuous flow Vortex Reactor (VR) and Semi-Batch Reactor (SBR). The effect of hydrodynamics by changing the Reynolds number of the jets providing residence times of 8.4 ms to 4.37 s for VR, and by changing the stirrer speed between 100 rpm (Re = 2656) and 1000 rpm (Re = 26560) for SBR, on the particle size, particle size distribution, and morphology of the particles was investigated for both systems. It has been shown that it is possible to produce pure phase hydroxyapatite nanoparticles in the desired morphology by changing production system, without resorting to additives. While VR produced rod-like particles with the crystallite size around 4 nm, SBR produced spherical particles with the crystallite size of around 5 nm.     

Nano‐hydroxyapatite (HAp) and hydroxyapatite/platinum (HAp/Pt) core shell nanorods: Development,structural study,and their catalytic activity

The development of a new kind of material that is a nanostructured catalytic material with an environmentally benign nature that can be used for alternative energy has acquired significance in recent years. In this context, the use of heterogeneous catalysts for the transesterification of vegetable oils has gained prominence due to their eco‐friendly and reusable nature. Hence in the present study, pure hydroxyapatite (HAp) and hydroxyapatite/platinum (HAp/Pt) nanostructured particles have been prepared successfully through a facile chemical method without templates and surfactants and their catalytic activity investigated for transesterification of natural vegetable oil to bioenergy (biodiesel). The textural and structural features of pure HAp and HAp/Pt were investigated using various characterization techniques such as x‐ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The elements present in the prepared nanostructures were confirmed through energy dispersive spectroscopy (EDS) and x‐ray photoelectron spectroscopy (XPS) techniques. The XPS analysis also confirms the metallic nature of the platinum in HAp/Pt. The specific surface area and porous nature of the prepared nanostructured catalysts were studied using the N₂ physisorption Brunauer‐Emmett‐Teller‐Barrett‐Joyner‐Halenda (BET‐BJH) method. The catalytic activity of the pure HAp nanoparticles and HAp/Pt core shell nanorods with the Simarouba glauca plant seed oil was investigated. The obtained results indicate that the pristine HAp nanoparticles and HAp/Pt core shell nanorods (NRs) show 91.4% and 87.1% fatty acid methyl ester (FAME) conversion, respectively, potentially offering environmental benign biocatalysts for biofuel production from natural feed stock.     

Precipitation of hydroxyapatite at 37 °C in a meso oscillatory flow reactor operated in batch at constant power density

A meso oscillatory flow reactor (meso‐OFR) was successfully applied for the precipitation of hydroxyapatite (HAp) nanoparticles. Mixing efficiency of the mesoreactor operated batchwise in a vertical tube was evaluated at constant power density, by monitoring variation of hue values upon mixing both spatially and temporally. The best operating conditions for fast mixing and a more homogeneous reaction medium were verified for f = 0.83 Hz and x₀ = 4.5 mm. HAp precipitation was then carried out under these conditions at 37 °C for different mixing Ca/P molar ratios. HAp nanoparticles with a mean size (d₅₀) of about 67 nm and a narrow size distribution were obtained. Furthermore, the obtained results show the advantages of the meso‐OFR over a stirred tank batch reactor due to the production, about four times faster, of smaller and more uniform HAp nanoparticles. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4483–4493, 2013     

Rapid synthesis of cesium-doped hydroxyapatite nanorods: characterisation and microbial activity

Rapid synthesis of cesium-doped hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, (HAp)) by rapid microwave synthesis technique is reported. The crystal, chemical, and dielectric properties, along with the phase composition and morphology were investigated. SEM study proved successful synthesis of HAp nanorods. The dielectric properties were affected by the doping amount of Cs-ions in HAp. The values of crystallinity degree at different concentrations of Cs-ions were decreased on increasing the Cs content. The antimicrobial activities of Cs-doped HAp showed high effects of growth inhibition on Staphylococcus aureus, S. saprophyticus, Escherichia coli, Haemophilus influenza, Candida albicans, and C. tropicalis. The concentration of 0.32 Cs-doped HAp has the high inhibition effect against S. aureus with the percentage of inhibition to 88.89%. The microbial inhibition growth reflected on the MICs and MBCs and MFCs. This newly designed Cs-doped HAp can be applicable in wide scales biomedical applications such as bone cement engineering and antimicrobial agents.     

Enhanced in vitro inhibition of MCF-7 and magnetic properties of cobalt incorporated calcium phosphate (HAp and β-TCP) nanoparticles

The Co²⁺ (0.1 M) incorporated hydroxyapatite (HAp) and beta tricalcium phosphate (β-TCP) nanoparticles were synthesized by the microwave assisted technique and sintering of HAp respectively. The samples were thermally treated at temperatures ranging from 200 to 1000°C. The partial substitutions of Co²⁺ at the Ca²⁺ site of HAp were confirmed from the slight shift (～0.2°) in the (002) and (211) XRD peaks. The morphology of the nanoparticles was transformed from nanospheres to twinned particles on thermal treatment. In addition, the particle size of Co-600 was increased (from ～50 nm to ～100 nm) due to the recrystallization process. Further, the thermal treatment enhanced the crystallinity (41.15 to 90.16%), retentivity (M_r) and coercivity (H_c) of the nanoparticles. The cobalt incorporated HAp and β-TCP possessed paramagnetic property. The excellent bioactivity of β-TCP has been confirmed by the mineralization in simulated body fluid (SBF). Compared to HAp, β-TCP possessed better compatibility towards C2C12 cells on cobalt incorporation as evidenced by the in vitro cell viability. Moreover, both HAp and β-TCP have significantly inhibited the growth of MCF-7 on increasing the interaction time (72 h). Hence, the inhibition characteristics of Co²⁺ incorporated calcium phosphate (CaP) towards MCF-7 (without affecting the normal cells) demonstrate its competency as a potential material for cancer therapy over the already existing nanoparticles.     

Enhancement of antimicrobial and long-term biostability of the zinc-incorporated hydroxyapatite coated 316L stainless steel implant for biomedical application

Antimicrobial hydroxyapatite (HAp) nanoparticles with different concentrations (0, 3, and 6 mol%) of zinc were prepared by the ultrasonication process. The prepared nanoparticles and chitosan (CTS) composite were coated on 316L stainless steel implant by spin coating technique. The powder samples were characterised by particle size analyser, X-ray fluorescence, and X-ray diffraction studies. The morphology of the coating was investigated by scanning electron microscopy. The diameter of the particle size decreased with increase in the concentration of zinc in HAp structure. The structure of the coated implant was found to be uniform without any cracks and pores. Antimicrobial activity of the composites against Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumonia, Salmonella typhi and Pseudomonas aeruginosa was analysed. The results showed that the increase in the concentration of zinc enhances the antimicrobial properties of 316L stainless steel implant. The stability of the implant in physiological environment was characterised by electrochemical impedance spectroscopy and polarisation analysis. The higher concentration of the ZnHAp/CTS composite shows higher corrosion resistance than that of the HAp/CTS-coated implant. This study shows that the coating provides corrosion resistance to the stainless steel substrate in simulated body fluid (SBF). The in vitro bioactivity study of the coated samples immersed in SBF solution confirms the formation of bone-like apatite layer on the surface of the implant. Thus, highly biocompatible ZnHAp/CTS-coated materials could be very useful in the long-term stability of the biomedical applications.     

In vitro evaluation of natural hydroxyapatite from Osteoglossum bicirrhosum fish scales for biomedical application

This study reports the obtainment of bioactive hydroxyapatite (HAp) extracted from scales of arowana fish (FSHA) (Osteoglossum bicirrhosum) by alkaline treatment followed by calcination at 600 and 800°C. The cell viability and bioactivity of hydroxyapatite particles (FSHA) were investigated and compared with those of HAp synthesized (s.HA) by the precipitation method. The HAp particles from fish scales showed non-toxic behavior to dental pulp stem cells similar to HAp synthesized. Additionally, bioactivity assays show that the Hap from natural source forms the bone-like apatite layer faster than s.HA sample, after being incubated in McCoy medium for 3 days. The results illustrate that HAp obtained from Osteoglossum bicirrhosum fish scale bio-waste showed excellent biocompatibility. Besides, this study provides an effective method for converting low-cost bio-waste into a value-added and it can be a potential alternative biomaterial for various biomedical applications.     

Synthesis and characterization of monetite and hydroxyapatite whiskers obtained by a hydrothermal method

High temperature hydrothermal syntheses, using calcium nitrate tetrahydrate, sodium dihydrogen phosphate and urea as precursors, and characterization of hydroxyapatite (HAp) whiskers are reported herein. The morphology and chemical composition of the crystals from a monetite to a hydroxyapatite phase were controlled by varying the starting concentrations of the precursors and the solution pH through the amount of urea that is decomposed during heating. X-ray diffraction (XRD) analysis, infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) were used to investigate the products of the syntheses in order to find the optimum reaction conditions for obtaining the desired morphology and phase composition. Different morphologies ranging from single crystals of monetite through rods and plates of hydroxyapatite with different size distribution to whisker-like single hydroxyapatite crystal were achieved by simply varying the starting concentration of urea. Structural refinement of the hydroxyapatite whiskers confirmed a strong preferential orientation along the c-axis direction of the hexagonal crystal structure, which was significantly different from the usually observed random crystal orientation. TEM and SEM analysis of the apatite whiskers confirmed single crystal structure with the a c-axis orientation parallel to the long axis of the whiskers, with sizes up to 150 μm in length, 10 μm in width and with a thickness of about 300 nm, that grew from the same centre of nucleation, forming flaky-like particles.