Spectroscopic investigations of nanohydroxyapatite powders synthesized by conventional and ultrasonic coupled sol-gel routes

Production of Nano Hydroxyapatite and Mg-Whitlockite from Biowaste-Derived products via Continuous Flow Hydrothermal Synthesis: A Step towards Circular Economy

Biowastes from agriculture, sewage, household wastes, and industries comprise promising resources to produce biomaterials while reducing adverse environmental effects. This study focused on utilising waste-derived materials (i.e., eggshells as a calcium source, struvite as a phosphate source, and CH₃COOH as dissolution media) to produce value-added products (i.e., calcium phosphates (CaPs) derived from biomaterials) using a continuous flow hydrothermal synthesis route. The prepared materials were characterised via XRD, FEG-SEM, EDX, FTIR, and TEM analysis. Magnesium whitlockite (Mg-WH) and hydroxyapatite (HA) were produced by single-phase or biphasic CaPs by reacting struvite with either calcium nitrate tetrahydrate or an eggshell solution at 200 °C and 350 °C. Rhombohedral-shaped Mg-WH (23-720 nm) along with tube (50-290 nm diameter, 20-71 nm thickness) and/or ellipsoidal morphologies of HA (273-522 nm width) were observed at 350 °C using HNO₃ or CH₃COOH to prepare the eggshell and struvite solutions, and NH₄OH was used as the pH buffer. The Ca/P (atomic%) ratios obtained ranged between 1.3 and 1.7, indicating the formation of Mg-WH and HA. This study showed that eggshells and struvite usage, along with CH₃COOH, are promising resources as potential sustainable precursors and dissolution media, respectively, to produce CaPs with varying morphologies.

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

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

Investigations on sonofragmentation of hydroxyapatite crystals as a function of strontium incorporation

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA) is chemically similar to the mineral component of bones and hard tissues in mammals. Various cations can substitute calcium in the crystal structure of hydroxyapatite. Among them strontium triggers interest, because strontium incorporated hydroxyapatite increases the number of bone forming sites in addition to having good biocompatibility. In the present investigation strontium substituted hydroxyapatite (SHA) in the compositions range 0, 10, 20, 50 and 100 mol% have been synthesized by precipitation method and subjected to ultrasonic treatment for different time intervals to gain insight on the role of ultrasound in modifying the morphology of SHA. This study reveals that the aspect ratio of SHA varied with the duration of ultrasonication. SHA samples subjected to 5 min ultrasound experienced an increase in aspect ratio. Further increase of ultrasonication time tends to decrease the aspect ratio invariably for all SHA samples indicating particle fragmentation. The extent of sonofragmentation as a function of percentage incorporation of strontium in HA lattice has been studied as a part of the present investigation. This study indicated that strain in the HA lattice has correlation with strontium incorporation, leading to varied extent of sonofragmentation. Also, the investigation suggested that 100% substitution of calcium sites by strontium leads to a relatively lesser strain and hence poor fragmentation. To the best of our knowledge the report on sonofragmentation of HA crystallites as a function of strontium incorporation is first of its kind in the literature.

Experimental, quantum chemical and molecular dynamic simulations studies on the corrosion inhibition of mild steel by some carbazole derivatives

Five selected carbazole derivatives, namely carbazole, 3,6-dibromocarbazole, 2-hydroxycarbazole, 1,2,3,4-tetrahydrocarbazole and 9-(2-ethylhexyl)carbazole-3,6-dicarboxaldehyde were investigated for their inhibitive effects on Desulfovibrio vulgaris (D. vulgaris) induced corrosion of mild steel and in 1 M HCl medium using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The carbazole derivatives were found to be mixed type inhibitors with predominantly cathodic inhibitive effects for mild steel in 1 M HCl. Surface morphology results showed the compounds formed adsorbed film on mild steel surface in both aqueous acid and sulphate reducing bacteria (SRB) media. Quantum chemical calculations were used to provide molecular based explanations for the inhibitive effects of the compounds. The interactions of the molecules with mild steel surface was simulated based on molecular dynamic simulations approach using Fe(110) crystal surface as representative metallic surface.

Low-cost composites based on porous titania-apatite surfaces for the removal of patent blue V from water: Effect of chemical structure of dye

Hydroxyapatite/titania nanocomposites (TiHAp) were synthesized from a mixture of a titanium alkoxide solution and dissolution products of a Moroccan natural phosphate. The simultaneous gelation and precipitation processes occurring at room temperature led to the formation of TiHAp nanocomposites. X-ray diffraction results indicated that hydroxyapatite and anatase (TiO2) were the major crystalline phases. The specific surface area of the nanocomposites increased with the TiO2 content. Resulting TiHAp powders were assessed for the removal of the patent blue V dye from water. Kinetic experiments suggested that a sequence of adsorption and photodegradation is responsible for discoloration of dye solutions. These results suggest that such hydroxyapatite/titania nanocomposites constitute attractive low-cost materials for the removal of dyes from industrial textile effluent.

Lecithin-based wet chemical precipitation of hydroxyapatite nanoparticles

Hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ nanoparticles have been successfully synthesized by the wet chemical precipitation method at 60 °C in the presence of biocompatible natural surfactant-lecithin. The composition and morphology of nanoparticles of hydroxyapatite synthesized with lecithin (nHAp-PC) was studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Size distribution for nanoparticles was measured by nanoparticle tracking analysis in NanoSight system. We discuss in details influence of lecithin concentration in reaction system on nHAp-PC morphology, as well as on size distributions and suspendability of nanoparticles. Product exhibits crystalline structure and chemical composition of hydroxyapatite, with visible traces of lecithin. Difference in surfactant amounts results in changes in particles morphology and their average size.

Synthesis and spectral characterization of silver/magnesium co-substituted hydroxyapatite for biomedical applications

The present work is aimed at the synthesis of antibacterial and bioactive silver/magnesium co-substituted hydroxyapatite (Ag/Mg-HAP) powders. For this purpose, firstly, different concentrations (0.5, 1.5, 2.5wt.%) of silver substituted HAP (Ag-HAP) powders were prepared by ultrasonic irradiation technique and were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Secondly, magnesium (Mg) is co-substituted as secondary material into Ag-HAP to offset the potential cytotoxicity of Ag, as higher concentration of Ag is toxic. The antibacterial activity of as-synthesized powders was evaluated by Escherichia coli (E. coli) and was found to be effectively high against bacterial colonization. Also, the in vitro cell-material interaction is evaluated with human osteosarcoma MG63 (HOS MG63) cells for cell proliferation. The results showed the evidence of cytotoxic effects of the higher concentration of Ag-HAP characterized by poor cellular viability whereas, Ag/Mg-HAP showed better cell viability indicating that co-substitution of Mg in Ag-HAP effectively offset the negative effects of Ag and improve performance compared with pure HAP. Thus, the as synthesized Ag/Mg-HAP will serve as a better candidate for biomedical applications with good antibacterial property and bone bonding ability.

Novel banana peel pectin mediated green route for the synthesis of hydroxyapatite nanoparticles and their spectral characterization

Hydroxyapatite [HAP, Ca10(PO4)6(OH)2] is the main inorganic component of natural bone and is widely used in various biomedical applications. In this paper, we have reported the synthesis of HAP nanoparticles by banana peel pectin mediated green template method. The pectin extracted from the peels of banana and its various concentrations were exploited in our study to achieve a controlled crystallinity, particle size as well as uniform morphology of HAP. The extracted pectin was characterized by spectral techniques like Fourier transform infrared spectroscopy (FTIR) for the functional group analysis, proton-1 nuclear magnetic resonance spectroscopy ((1)H NMR) and carbon-13 nuclear magnetic resonance spectroscopy ((13)C NMR) for the identification of H and C atoms in the extracted pectin, respectively. The HAP nanoparticles were synthesized using different concentrations of the as-extracted pectin. The purity, crystallinity and morphology of the as-synthesized HAP nanoparticles were evaluated by FTIR, X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX) and transmission electron microscopy (TEM), respectively. Moreover the antibacterial activity of HAP nanoparticles was evaluated against the gram positive and negative bacteria like Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively. The experimental results revealed that the HAP nanoparticles synthesized in the presence of an optimized concentration of pectin are pure, low crystalline, spherical and discrete particles with reduced size. Also, the HAP sample derived in the presence of pectin showed an enhanced antibacterial activity than that of the HAP synthesized in the absence of pectin. Hence, the HAP nanoparticles synthesized using pectin as a green template can act as a good biomaterial for biomedical applications.

A novel green template assisted synthesis of hydroxyapatite nanorods and their spectral characterization

Hydroxyapatite [HAP, Ca10(PO4)6(OH)2] is the main inorganic component of bone material and is widely used in various biomedical applications due to its excellent bioactivity and biocompatibility. In this paper we have reported the synthesis of hydroxyapatite nanorods by green template method using the extracts of three different natural sources which contain tartaric acid and also from commercially available one. The extracts of banana, grape and tamarind are taken as the sources of tartaric acid. The as-synthesized samples were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Also the antibacterial activity of HAP with different concentrations against two pathogen bacteria strains Escherichia coli (E. coli) and Klebsiella (Gram-negative bacteria) were tested. The results show that the particles of all the samples are of nanosized and pure. The crystallinity decreases as changing the sources of tartaric acid from commercial to natural one and also changing the natural sources from banana to tamarind extracts. The formation of nanorods are found in all the samples but the nanorods with uniform size distribution can be obtained only by using the tamarind extract as the source of tartaric acid. Moreover, the as-synthesised HAP nanorods derived from natural sources exhibited a strong antibacterial activity against both E. coli and Klebsiella at a concentration of 100 μl. The HAP nanorods synthesized by this method can act as a potential candidate for various biomedical applications.

Synthesis and spectroscopic investigations of hydroxyapatite using a green chelating agent as template

Hydroxyapatite [Ca(10)(PO(4))(6)(OH)(2), HAP] particles have been successfully synthesized by a cost-effective, eco-friendly green template method using natural and commercially available sucrose as a chelating agent. The sucrose used in this method has been extracted from various sources, three from natural and one from commercially available sources are exploited in our study to achieve a controlled crystallinity, particle size as well as uniform morphology. Spectral characterizations involving Fourier transform infrared spectroscopy (FT-IR) for the functional group analysis of sucrose and HAP; carbon-13 nuclear magnetic resonance spectroscopy ((13)C NMR) for the identification of the carbon atoms in sucrose and in HAP; liquid chromatography/mass spectrometry (LC-MS) for the determination of the hydrolyzed products of sucrose; and X-ray diffraction (XRD) techniques for the phase identification of the HAP particles were performed. The morphology of the HAP particles were assessed thoroughly using a scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDAX). The experimental results indicate that the obtained HAP using the natural sucrose as a chelating agent is of phase pure, with a well defined morphology having discrete particles without any agglomeration than the HAP from commercially available sucrose. Further, the reduced particle size can be achieved from the stem sugarcane extract as the source of the chelating agent.

Hydroxyapatite nanoparticles as vectors for gene delivery

The long-recognized promise of gene therapy to treat a broad range of currently incurable diseases remains largely unfulfilled, hindered by lack of a safe and efficient delivery vehicle. Hydroxyapatite nanoparticles are deemed a feasible candidate and possess many characteristics desired of an ideal gene vector. Current fabrication techniques can readily synthesize hydroxyapatite particles in the nanometer range; however, these particles suffer from extensive aggregation and heterogeneity, mainly in size, shape and surface charge, which render them inappropriate for gene-therapy application. There is thus a pertinent need to develop a method capable of fabricating homogenous and monodispersed hydroxyapatite nanoparticles in a rapid, efficient and cost-effective manner that can be easily upscaled. Cell transfection is impeded by several physical and biological barriers, with the vector's properties highly determinant of its ability to overcome these barriers. Fine-tuning hydroxyapatite nanoparticles' morphological and physicochemical properties, achievable through precise regulation of the reaction environment, can enhance transfection efficiencies of particles, in turn, generating safe and effective gene vectors.

Synthesis of hydroxyapatite nanoparticles by a novel ultrasonic assisted with mixed hollow sphere template method

Hydroxyapatite (HAP) is the main inorganic component of bone material and is widely used in various biomedical applications due to its excellent bioactivity and biocompatibility. In this paper, we have reported the synthesis of hydroxyapatite nanoparticles by a novel ultrasonic assisted mixed template directed method. In this method glycine-acrylic acid (GLY-AA) hollow spheres were used as an organic template which could be prepared by mixing of glycine with acrylic acid. The as-synthesized HAP nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and tunnelling electron microscope (TEM) to investigate the nature of bonding, crystallinity, size and shape. The thermal stability of as-synthesized nanoparticles was also investigated by the thermo gravimetric analysis (TGA). The effect of ultrasonic irradiation time on the crystallinity and size of the HAP nanoparticles in presence of glycine-acrylic acid hollow spheres template were investigated. From the inspection of the above results it is confirmed that the crystallinity and size of the HAP nanoparticles decrease with increasing ultrasonic irradiation time. Hence the proposed synthesis strategy provides a facile pathway to obtain nano sized HAP with high quality, suitable size and morphology.

Spectroscopic investigation on formation and growth of mineralized nanohydroxyapatite for bone tissue engineering applications

Synthetic calcium hydroxyapatite (HAP,Ca(10)(PO(4))(6)(OH)(2)) is a well-known bioceramic material used in orthopaedic and dental applications because of its excellent biocompatibility and bone-bonding ability. Substitution of trace elements, such as Sr, Mg and Zn ions into the structure of calcium phosphates is the subject of widespread investigation. In this paper, we have reported the synthesis of Sr, Mg and Zn co-substituted nanohydroxyapatite by soft solution freezing method. The effect of pH on the morphology of bioceramic nanomaterial was also discussed. The in vitro bioactivity of the as-synthesized bioceramic nanomaterial was determined by soaking it in SBF for various days. The as-synthesized bioceramic nanomaterial was characterized by Fourier transform infrared spectroscopy, X- ray diffraction analysis, Scanning electron microscopy and Energy dispersive X-ray analysis and Transmission electron microscopic techniques respectively. The results obtained in our study have revealed that pH 10 was identified to induce the formation of mineralized nanohydroxyapatite. It is observed that the synthesis of bioceramic nanomaterial not only support the growth of apatite layer on its surface but also accelerate the growth which is evident from the in vitro studies. Therefore, mineralized nanohydroxyapatite is a potential candidate in bone tissue engineering.

Synthesis and spectroscopic characterization of magnetic hydroxyapatite nanocomposite using ultrasonic irradiation

Nowadays magnetic hydroxyapatite (m-HAP) has potential applications in biomedicine more especially for bone cancer treatment. In this paper the functionalization of the hydroxyapatite (HAP) with magnetite nanoparticle (MNP) through ultrasonic irradiation technique is reported and its spectral investigation has been carried out. The ultrasonic irradiation with two different frequencies of 28kHz and 35kHz at the power of 150 and 320W, respectively, was employed for the synthesis of m-HAP. The ultrasound irradiation of 35kHz at 320W shows the efficient diffusion of MNP to the HAP host matrix leads to the formation of m-HAP. The ultrasonic irradiation technique does not require stabilizers as in the case of coprecipitation method hence the final product of pure m-HAP is obtained. The X-ray diffraction pattern shows the formation of magnetite nanoparticles which are functionalized with hydroxyapatite host matrix. The vibrating sample magnetometer curve exhibits the super paramagnetic property of the samples and the saturation magnetization (M(s)) value of the functionalized magnetic hydroxyapatite. The M(s) value is found to be much less than that of pure magnetite nanoparticle and this decrement in M(s) is due to the hindrance of magnetic domain of the particles with HAP. The portrayed Raman spectra discriminate between the m-HAP and MNP with corresponding vibrational modes of frequencies. The transmission electron micrograph shows excellent morphology of functionalized m-HAP in nanometer range. The atomic force microscopic investigation shows the 3-dimensional view of crust and trench shape of m-HAP. All these results confirm the formation of magnetic hydroxyapatite nanocomposite with typical magnetic property for biological applications.

Nanoscale hydroxyapatite particles for bone tissue engineering

Hydroxyapatite (HAp) exhibits excellent biocompatibility with soft tissues such as skin, muscle and gums, making it an ideal candidate for orthopedic and dental implants or components of implants. Synthetic HAp has been widely used in repair of hard tissues, and common uses include bone repair, bone augmentation, as well as coating of implants or acting as fillers in bone or teeth. However, the low mechanical strength of normal HAp ceramics generally restricts its use to low load-bearing applications. Recent advancements in nanoscience and nanotechnology have reignited investigation of nanoscale HAp formation in order to clearly define the small-scale properties of HAp. It has been suggested that nano-HAp may be an ideal biomaterial due to its good biocompatibility and bone integration ability. HAp biomedical material development has benefited significantly from advancements in nanotechnology. This feature article looks afresh at nano-HAp particles, highlighting the importance of size, crystal morphology control, and composites with other inorganic particles for biomedical material development.

Spectroscopic characterization of nanohydroxyapatite synthesized by molten salt method

Hydroxyapatite (HAP) nanopowders were synthesized by molten salt method at 260 degrees C. The as-prepared powders were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and thermo gravimetric analysis (TGA). With the aid of the obtained results the effect of calcining time on the crystallinity, size and morphology of HAP nanopowders is presented. The HAP nanopowders synthesized by molten salt method consist of pure phase of HAP without any impurities and showed the rod-like morphology without detectable decomposition up to 1100 degrees C.

Spectroscopic characterization of porous nanohydroxyapatite synthesized by a novel amino acid soft solution freezing method

In this paper, we have reported a novel method to synthesize nanoporous hydroxyapatite (HAP) powders by freezing organic-inorganic soft solutions. The formation of porous and crystalline HAP nanopowder was achieved via calcining the samples at 600 degrees C followed by sintering at temperatures ranging from 900 degrees C to 1100 degrees C. The samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopic (SEM) techniques. The results showed the formation of a carbon free nanoporous hydroxyapatite powders due to the decomposition of organic template enclosing the precipitated HAP. It was also observed that the rapid grain growth with retainment of pores while the crystallinity of the HAP nanopowder increased with the increase in sintering temperature which is substantiated from the XRD and SEM results. Such organized porous materials can act as a better biomaterial for bone tissue engineering.