Monetite Formed in Mixed Solvents of Water and Ethylene Glycol and Its Transformation to Hydroxyapatite

Optimization of a tunable process for rapid production of calcium phosphate microparticles using a droplet-based microfluidic platform

Calcium phosphate (CaP) biomaterials are amongst the most widely used synthetic bone graft substitutes, owing to their chemical similarities to the mineral part of bone matrix and off-the-shelf availability. However, their ability to regenerate bone in critical-sized bone defects has remained inferior to the gold standard autologous bone. Hence, there is a need for methods that can be employed to efficiently produce CaPs with different properties, enabling the screening and consequent fine-tuning of the properties of CaPs towards effective bone regeneration. To this end, we propose the use of droplet microfluidics for rapid production of a variety of CaP microparticles. Particularly, this study aims to optimize the steps of a droplet microfluidic-based production process, including droplet generation, in-droplet CaP synthesis, purification and sintering, in order to obtain a library of CaP microparticles with fine-tuned properties. The results showed that size-controlled, monodisperse water-in-oil microdroplets containing calcium- and phosphate-rich solutions can be produced using a flow-focusing droplet-generator microfluidic chip. We optimized synthesis protocols based on in-droplet mineralization to obtain a range of CaP microparticles without and with inorganic additives. This was achieved by adjusting synthesis parameters, such as precursor concentration, pH value, and aging time, and applying heat treatment. In addition, our results indicated that the synthesis and fabrication parameters of CaPs in this method can alter the microstructure and the degradation behavior of CaPs. Overall, the results highlight the potential of the droplet microfluidic platform for engineering CaP microparticle biomaterials with fine-tuned properties.

Fabrication, Properties, and Biomedical Applications of Calcium-Containing Cellulose-Based Composites

Calcium-containing cellulose-based composites possess the advantages of high mechanical strength, excellent osteoconductivity, biocompatibility, biodegradation, and bioactivity, which represent a promising application system in the biomedical field. Calcium-containing cellulose-based composites have become the hotspot of study of various biomedical fields. In this mini-review article, the synthesis of calcium-containing cellulose-based composites is summarized via a variety of methods such as the biomimetic mineralization method, microwave method, co-precipitation method, hydrothermal method, freeze-drying method, mechanochemical reaction method, and ultrasound method. The development on the fabrication, properties, and applications of calcium-containing cellulose-based composites is highlighted. The as-existed problems and future developments of cellulose-based composites are provided. It is expected that calcium-containing cellulose-based composites are the ideal candidate for biomedical application.

Recrystallization of Triple Superphosphate Produced from Oyster Shell Waste for Agronomic Performance and Environmental Issues

Calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2·H2O) (a fertilizer) was successfully synthesized through a recrystallization process using prepared triple superphosphate (TSP) derived from oyster shell waste as the starting material. This bio-green, eco-friendly process to produce an important fertilizer can promote a sustainable society. The shell-waste-derived TSP was dissolved in distilled water and kept at 30, 50, and 80 °C. Non-soluble powder and TSP solution were obtained. The TSP solution fractions were then dried, and the recrystallized products (RCP30, RCP50, and RCP80) were obtained and confirmed as Ca(H2PO4)2·H2O. Conversely, the non-soluble products (NSP30, NSP50, and NSP80) were observed as calcium hydrogen phosphate dihydrate (CaHPO4·2H2O). The recrystallized yields of RCP30, RCP50, and RCP80 were found to be 51.0%, 49.6%, and 46.3%, whereas the soluble percentages were 98.72%, 99.16%, and 96.63%, respectively. RCP30 shows different morphological plate sizes, while RCP50 and RCP80 present the coagulate crystal plates. X-ray diffractograms confirmed the formation of both the NSP and RCP. The infrared adsorption spectra confirmed the vibrational characteristics of HPO42−, H2PO4−, and H2O existed in CaHPO4·2H2O and Ca(H2PO4)2·H2O. Three thermal dehydration steps of Ca(H2PO4)2·H2O (physisorbed water, polycondensation, and re-polycondensation) were observed. Ca(H2PO4)2 and CaH2P2O7 are the thermodecomposed products from the first and second steps, whereas the final product is CaP2O6.

Solvothermal Synthesis of Calcium-Deficient Hydroxyapatite via Hydrolysis of α-Tricalcium Phosphate in Different Aqueous-Organic Media

In the present work, the effects of various organic solvents (solvent nature and fraction within the solution) and solvothermal conditions on the formation of calcium-deficient hydroxyapatite (CDHA) via hydrolysis of α-tricalcium phosphate (α-TCP) are investigated. The wet precipitation method is applied for α-TCP synthesis, and the hydrolysis reaction is performed in solutions with different water-to-organic solvent ratios under solvothermal conditions at 120 °C for 3 h and at 200 °C for 5 h. Ethyl alcohol, isopropyl alcohol, and butyl alcohol did not inhibit the hydrolysis of α-TCP, while methyl alcohol and ethylene glycol have a more prominent inhibitory effect on the hydrolysis, hence the formation of single-phased CDHA. From all the solvents analysed, ethylene glycol has the highest impact on the sample morphology. Under certain water to ethylene glycol ratios and solvothermal conditions, samples containing a significant fraction of rods are obtained. However, samples prepared with ethylene glycol are characterised by a particularly low BET surface area.

Calcium hydroxyapatite nanoparticles as a reinforcement filler in dental resin nanocomposite

The current study focuses on the fabrication of calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) (HA) in a nanorange having whiskers- and cubic-shaped uniform particle morphology. The synthesized HA particles hold a promising feature as reinforcement fillers in dental acrylic resin composite. They increase the efficacy of reinforcement by length and aspect ratio, uniformity, and monodispersity. Therefore, the acrylic resin was reinforced with the as-synthesized monodispersed HA filler particles (0.2-1 Wt%). The presence of filler particles in the composite had a noticeable effect on the tribological and mechanical properties of the dental material. The morphological effect of HA particles on these properties was also investigated, revealing that cubic-shaped particles showed better results than whiskers. The as-fabricated composite (0.4 Wt%) of the cubic-shaped filler particles showed maximum hardness and improved antiwear/antifriction properties. Particle loading played its part in determining the optimum condition, whereas particle size also influenced the reinforcement efficiency. The current study revealed that particle morphology, particle size, uniformity, etc., of HA fillers, greatly influenced the tribological and mechanical properties of the acrylic resin-based nanocomposite. Improvement in the tribological properties of HA particle-reinforced acrylic resin composites (HA-acrylic resin) followed the trend as AR < C_mC < WC < CC.

Fabrication and properties of alginate/calcium phosphate hybrid beads: A comparative study

BACKGROUND

Microbeads for bone repair have been widely studied because they can be conveniently used in clinical applications.

OBJECTIVE

This study concerns the preparation, physical properties and in vitro characterisation of different types of alginate/calcium phosphate (CaP) ceramic microbeads, which were designed for use as drug delivery systems and bone-regeneration matrices.

METHODS

Hybrid microbeads were successfully prepared from sodium alginate and various CaP, namely 𝛼-tricalcium phosphate, 𝛽-tricalcium phosphate and hydroxyapatite using the liquid droplet method.

RESULTS

Porosity, swelling properties and in vitro degradation of the microbeads in the aqueous environment were significantly changed by the added CaP. The compressive strength of the blocks fabricated from the beads was around 120 MPa irrespective of the type of CaP. The initial release rate of the model drug methylene blue was suppressed by the addition of CaP.

CONCLUSION

The alginate-CaP composite beads hold promising potential as an encapsulation carrier of drugs and component of bone substitutes.

Monetite, an important calcium phosphate compound-Its synthesis, properties and applications in orthopedics

This review recognizes a unique calcium phosphate (CaP) phase known as monetite or dicalcium phosphate anhydrous (DCPA, CaHPO₄), and presents an overview of its properties, processing, and applications in orthopedics. The motivation for the present effort is to highlight the state-of-the-art research and development of monetite and propel the research community to explore more of its potentials in orthopedics. After a brief introduction of monetite, we provide a summary of its various synthesis routes like dehydration, solvent-based, energy-assisted processes and also discuss the formation of different crystal structures with respect to the synthesis conditions. Subsequently, we discuss the material's noteworthy physico-chemical properties including the crystal structure, vibrational spectra, solubility, thermal decomposition, and conversion to other phases. Of note, we focus on the biological (in vitro and in vivo) properties of monetite, given its ever-increasing popularity as a biomaterial for medical implants. Appropriately, we discuss various orthopedic applications of monetite as bone cement, implant coatings, granules for defect fillers, and scaffolds. Many in vitro and in vivo studies confirmed the favorable osteointegration and osteoconduction properties of monetite products, along with a better balance between implant resorption and new bone formation as compared to other CaP phases. The review ends with translational aspects of monetite and presents thoughts about its possible future research directions. Further research may explore but not limited to improvements in mechanical strength of monetite-based scaffolds, using monetite particles as a therapeutic agent delivery, and tissue engineering strategies where monetite serves as the biomaterial. STATEMENT OF SIGNIFICANCE: This is the first review that focusses on the favorable potential of monetite for hard tissue repair and regeneration. The article accurately covers the "Synthesis-Structure-Property-Applications" correlations elaborating on monetite's diverse material properties. Special focus is put on the in vitro and in vivo properties of the material highlighting monetite as an orthopedic material-of-choice. The synthesis techniques are discussed which provide important information about the different fabrication routes for monetite. Most importantly, the review provides comprehensive knowledge about the diverse biomedical applications of monetite as granules, defect--specific scaffolds, bone cements and implant coatings. This review will help to highlight monetite's potential as an effective regenerative medicine and catalyze the continuing translation of this bioceramic from the laboratory to clinics.

Surfactant-assisted synthesis of polyvinylpyrrolidone-hydroxyapatite composites as a bone filler

BACKGROUND

Different methods have been used to prepare bone-like composites from inorganic nanoparticles embedded in polymeric matrixes to obtain the properties and structures required for bone fillers.

METHODS

Bone-like nano-hydroxyapatite (nHA) was synthesized using a biomimetic method, with polyvinylpyrrolidone (PVP) as template and sodium dodecyl sulfate (SDS) as surfactant.

RESULTS

The results demonstrated the formation of HA composites and showed that polymer and surfactant as the polymer capsule can be properly used to control the size, shape, morphology and dispersion of HA crystals. All of the samples were bioactive due to their ability to form carbonate apatite and grow HA on their surface. The MTT assay showed that the samples were biocompatible.

CONCLUSIONS

Based on bioactivity and biocompatibility evaluations, the prepared composites can be considered as good candidates for bone filler applications.

Biodegradable/biocompatible coated metal implants for orthopedic applications

Biocompatible metals have been suggested as revolutionary biomaterials for bone-grafting therapies. Although metals and their alloys are widely and successfully used in producing biomedical implants due to their good mechanical properties and corrosion resistance, they have a lack in bioactivity. Therefore coating of the metal surface with calcium phosphates (CaP) is a benign way to achieve well bioactivity and get controlled corrosion properties. The biocompatibility and bioactivity calcium phosphates (CaP) in bone growth were guided them to biomedical treatment of bone defects and fractures. Many techniques have been used for fabrication of CaP coatings on metal substrates such as magnesium and titanium. The present review will focus on the synthesis of CaP and their relative forms using different techniques especially electrochemical techniques. The latter has always been known of its unique way of optimizing the process parameters that led to a control in the structure and characteristics of the produced materials.

Direct Synthesis of Nitriles from Aldehydes and Hydroxylamine Hydrochloride Catalyzed by a HAP@AEPH2-SO3H Nanocatalyst

We describe an efficient method for the direct preparation of nitriles from aldehydes and hydroxylamine hydrochloride catalyzed by sulfonated nanohydroxyapatite functionalized by 2-aminoethyl dihydrogen phosphate (HAP@AEPH2-SO3H) as an eco-friendly and recyclable solid acid nanocatalyst. In this protocol the use of a solid acid nanocatalyst provides a green, useful, and rapid method for the preparation of nitriles in excellent yields. In addition, the notable feature of this methodolgy is that the synthesized nanocatalyst can be recovered and reused five times without any noticeable loss of efficiency.

Highly Flexible Superhydrophobic and Fire-Resistant Layered Inorganic Paper

Traditional paper made from plant cellulose fibers is easily destroyed by either liquid or fire. In addition, the paper making industry consumes a large amount of natural trees and thus causes serious environmental problems including excessive deforestation and pollution. In consideration of the intrinsic flammability of organics and minimizing the effects on the environment and creatures, biocompatible ultralong hydroxyapatite nanowires are an ideal building material for inorganic fire-resistant paper. Herein, a new kind of free-standing, highly flexible, superhydrophobic, and fire-resistant layered inorganic paper has been successfully prepared using ultralong hydroxyapatite nanowires as building blocks after the surface modification with sodium oleate. During the vacuum filtration, ultralong hydroxyapatite nanowires assemble into self-roughened setalike microfibers, avoiding the tedious fabrication process to construct the hierarchical structure; the self-roughened microfibers further form the inorganic paper with a nacrelike layered structure. We have demonstrated that the layered structure can significantly improve the resistance to mechanical destruction of the as-prepared superhydrophobic paper. The as-prepared superhydrophobic and fire-resistant inorganic paper shows excellent nonflammability, liquid repellency to various commercial drinks, high thermal stability, and self-cleaning property. Moreover, we have explored the potential applications of the superhydrophobic and fire-resistant inorganic paper as a highly effective adsorbent for oil/water separation, fire-shielding protector, and writing paper.

Hydrothermally processed 1D hydroxyapatite: Mechanism of formation and biocompatibility studies

Recent developments in bone tissue engineering have led to an increased interest in one-dimensional (1D) hydroxyapatite (HA) nano- and micro-structures such as wires, ribbons and tubes. They have been proposed for use as cell substrates, reinforcing phases in composites and carriers for biologically active substances. Here we demonstrate the synthesis of 1D HA structures using an optimized, urea-assisted, high-yield hydrothermal batch process. The one-pot process, yielding HA structures composed of bundles of ribbons and wires, was typified by the simultaneous occurrence of a multitude of intermediate reactions, failing to meet the uniformity criteria over particle morphology and size. To overcome these issues, the preparation procedure was divided to two stages: dicalcium phosphate platelets synthesized in the first step were used as a precursor for the synthesis of 1D HA in the second stage. Despite the elongated particle morphologies, both the precursor and the final product exhibited excellent biocompatibility and caused no reduction of viability when tested against osteoblastic MC3T3-E1 cells in 2D culture up to the concentration of 2.6mg/cm(2). X-ray powder diffraction combined with a range of electron microscopies and laser diffraction analyses was used to elucidate the formation mechanism and the microstructure of the final particles. The two-step synthesis involved a more direct transformation of DCP to 1D HA with the average diameter of 37nm and the aspect ratio exceeding 100:1. The comparison of crystalline domain sizes along different crystallographic directions showed no signs of significant anisotropy, while indicating that individual nanowires are ordered in bundles in the b crystallographic direction of the P63/m space group of HA. Intermediate processes, e.g., dehydration of dicalcium phosphate, are critical for the formation of 1D HA alongside other key aspects of this phase transformation, it must be investigated in more detail in the continuous design of smart HA micro- and nano-structures with advanced therapeutic potentials.

Amelogenin Affects Brushite Crystal Morphology and Promotes Its Phase Transformation to Monetite

Amelogenin protein is involved in organized apatite crystallization during enamel formation. Brushite (CaHPO₄·2H₂O), one of the precursors of hydroxyapatite mineralization in vitro, has been used for fabrication of biomaterials for hard tissue repair. In order to explore its potential application in biomimetic material synthesis, we studied the influence of the enamel protein amelogenin on brushite morphology and phase transformation to monetite. Our results show that amelogenin can adsorb onto the surface of brushite, leading to the formation of layered morphology on the (010) face. Amelogenin promoted the phase transformation of brushite into monetite (CaHPO₄) in the dry state, presumably by interacting with crystalline water layers in brushite unit cells. Changes to the crystal morphology mediated by amelogenin continued even after the phase transformation from brushite to monetite, leading to the formation of organized platelets with an interlocked structure. This effect of amelogenin on brushite morphology and the phase transformation to monetite could provide a new approach to developing biomimetic materials.

The synergetic effect of nano-structures and silicon-substitution on the properties of hydroxyapatite scaffolds for bone regeneration

Control over the morphology and chemical composition of hydroxyapatite (HAp) bioceramic scaffolds is of great importance for their applications. In the present study, Si-substituted HAp bioceramic scaffolds with controllable morphologies (nanosheets and nanorods) were fabricated via hydrothermal treatment of calcium silicate scaffolds as precursors in NaH₂PO₄ and Na₃PO₄ aqueous solutions, respectively. Moreover, the effects of surface morphologies and Si substitution on cell attachment, proliferation, and osteogenic differentiation of rat bone marrow stromal cells (rBMSCs) were systematically investigated in vitro. The results showed that nano-topography surfaces could enhance cell attachment, cell proliferation, alkaline phosphatase (ALP) activity, and mRNA expression levels of collagen 1 (COL1), bone morphogenetic protein 2 (BMP-2), bone sialoprotein (BSP) and osteopontin (OPN). Moreover, the Si substitution could further promote cell proliferation and osteogenic differentiation, while Si-substituted bioceramics with a nanorod surface possessed the highest stimulatory effect. More importantly, the in vivo rat critical-sized calvarial defect model confirmed that HAp bioceramic scaffolds with nanosheet and nanorod surfaces showed definitive bone regeneration as compared with control HAp bioceramic scaffolds with a traditional smooth surface. Moreover, Si substitution could synergistically enhance bone regeneration and mineralization, while Si-substituted HAp bioceramic scaffolds with a nanorod surface achieved the best bone repair ability. The present study suggests that the modification of the surface morphology and Si substitution on the HAp bioceramic scaffold may be an effective synergistic strategy to improve its clinical performance.

Synthesis of calcium phosphate crystals with thin nacreous structure

Calcium phospate crystals with a thin nacreous structure were synthesized and characterized.

Hierarchical One-Dimensional Ammonium Nickel Phosphate Microrods for High-Performance Pseudocapacitors

High-performance electrochemical capacitors will drive the next-generation portable, flexible and wearable electronics. Unlike the conventional all-carbon supercapacitors (electric double layer capacitors, EDLC) with high power but poor energy density, pseudocapacitors capitalize the high energy density inherent to reversible redox reactions and provide a facile means to enhancing the energy ratings of supercapacitors. The high length-to-diameter ratio and anisotropic character of 1-D architecture makes them suitable for use in energy storage. For the first time, we report 1-D microrod structures (~ 36 nm width) of ammonium nickel phosphate hydrate (ANP_mr) as a pseudocapacitor with high energy rating and power handling. To confirm the data, the ANP_mr-based pseudocapacitor was subjected to various configurations (i.e., half-cell, symmetric, asymmetric, and flexible all-solid-state) and in each case it gave excellent values compared to any accessible literature to date. We clearly demonstrate that a flexible all-solid-state ANP_mr-based pseudocapacitor achieved high areal capacitance of 66 mF cm⁻² with extra-ordinary energy (21.2 mWh cm⁻²) and power (12.7 mW cm⁻²) densities. This work opens doors for a facile, robust and scalable preparation strategy for low-cost, earth-abundant electrode materials for high-performance pseudocapacitors.

Amorphous calcium phosphate, hydroxyapatite and poly(d,l-lactic acid) composite nanofibers: Electrospinning preparation, mineralization and in vivo bone defect repair

Due to the outstanding bioactivity and biocompatibility, calcium phosphate (CaP) based materials have been widely investigated for applications in the biomedical fields. In this study, amorphous calcium phosphate (ACP) nanospheres and hydroxyapatite (HA) nanorods have been prepared and hybridized with poly(d,l-lactic acid) (PLA) to fabricate the composite nanofibers through electrospinning. The as-prepared ACP-PLA and HA-PLA composite nanofibers exhibit favorable mineralization behaviors in simulated body fluid (SBF). In the mineralization process, the ACP nanospheres and HA nanorods play an important role in the formation of HA nanosheets on the surface of composite nanofibers. The ACP-PLA and HA-PLA composite nanofibers show a high biocompatibility. The in vivo bone defect repair properties of the ACP-PLA and HA-PLA composite nanofibers are preliminarily investigated. The as-prepared ACP-PLA and HA-PLA composite nanofibers have promising applications in the biomedical fields.

Enhanced defluoridation and facile separation of magnetic nano-hydroxyapatite/alginate composite

In this research study, a new magnetic biosorbent was developed by the fabrication of magnetic Fe3O4 particles on nano-hydroxyapatite(n-HAp)/alginate (Alg) composite (Fe3O4@n-HApAlg composite) for defluoridation in batch mode. The synthesized Fe3O4@n-HApAlg biocomposite possess an enhanced defluoridation capacity (DC) of 4050 mgF(-)/kg when compare to n-HApAlg composite, Fe3O4@n-HAp composite, n-HAp and Fe3O4 which possesses the DCs of 3870, 2469, 1296 and 1050 mgF(-)/kg respectively. The structural changes of the sorbent, before and after fluoride sorption were studied using FTIR, XRD and SEM with EDAX techniques. There are various physico-chemical parameters such as contact time, pH, co-existing anions, initial fluoride concentration and temperature were optimized for maximum fluoride removal. The equilibrium data was well modeled by Freundlich, Langmuir, Dubinin-Radushkevich (D-R) and Temkin isotherms. The present system follows Dubinin-Radushkevich isotherm model. The thermodynamic parameters reveals that the feasibility, spontaneity and endothermic nature of fluoride sorption. The performance and efficiency of the adsorbent material was examined with water samples collected from fluoride endemic areas namely Reddiyarchatram and Ammapatti in Dindigul District of Tamil Nadu using standard protocols.

Effect of Citrate and Hexadecyltrimethylammonium Bromide on the Formation of Hydroxyapatite Crystal in a Thermal Aqueous Solution

To calrify the combined effect of soft template and biominormolecule on the formation of hydroxyapatite (HAp), the study on the growth of HAp regulated by citrate and(or) hexadecyltrimethylammonium bromide (CTAB) solution was developed in a thermal aqueous. The as-obtained products were characterized by XRD, FT-IR and TEM, altogether with HRTEM and ED. Plate-like HAp crystals in nanosize with relative weak crystallinity were obtained in the presence of citrate. Nano-needle shape HAp crystals were produced in the presence of CTAB. Rod-like HAp crystals in a uniform nanosize were formed under the regulation of CTAB and citrate, which showed the same orientation as that of CTAB only. However, the possible mechanism of the growth of HAp was discussed in detail. CTAB micelles worked as a soft template modified by citrate, which guided to form HAp crystals in different morphology. The study is benefit to control the formation of HAp for its bioapplication.

Sulfonated nanohydroxyapatite functionalized with 2-aminoethyl dihydrogen phosphate (HAP@AEPH2-SO3H) as a new recyclable and eco-friendly catalyst for rapid one-pot synthesis of 4,4′-(aryl methylene)bis(3-methyl-1H-pyrazol-5-ol)s

HAP@AEPH₂-SO₃H, a new, green, solid acid catalyst, was prepared, characterized and applied for the synthesis of 4,4′-(aryl methylene)bis(3-methyl-1H-pyrazol-5-ol)s.

Hollow hydroxyapatite spheres fabrication with three-dimensional hydrogel template

Flower-like porous hollow HAp spheres were obtained by diffusion of phosphate ions into PAAm hydrogels containing calcium ions by both an electrophoresis approach and an ion diffusion method.

Obtaining Ca(H2PO4)(2)·H2O, monocalcium phosphate monohydrate, via monetite from brushite by using sonication

Brushite was synthesized by precipitation of calcium chloride (CaCl(2)) and sodium phosphate monobasic (Na(2)HPO(4)) dried in vacuum and monetite was obtained from this brushite by sonication with a frequency of 90kHz at 500W for 90min. Monetite itself was also transformed in Ca(H(2)PO(4))(2)·H(2)O, monocalcium phosphate monohydrate (MCPM), by sonication with a frequency of 90kHz at 500W for 60min followed by lyophilization. The MCPM was sonicated and lyophilized by three times more until reach over 240min, but any other phase transformation was observed. All these phase transformations were analyzed by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated a grain size of about 200nm in all the samples. The morphology observed was a corn-flake-like grain for brushite, a pseudo-needle-like grains for monetite, and lamellar-like grains for MCPM.

Hierarchically nanostructured hydroxyapatite: hydrothermal synthesis, morphology control, growth mechanism, and biological activity

Hierarchically nanosized hydroxyapatite (HA) with flower-like structure assembled from nanosheets consisting of nanorod building blocks was successfully synthesized by using CaCl(2), NaH(2)PO(4), and potassium sodium tartrate via a hydrothermal method at 200°C for 24 hours. The effects of heating time and heating temperature on the products were investigated. As a chelating ligand and template molecule, the potassium sodium tartrate plays a key role in the formation of hierarchically nanostructured HA. On the basis of experimental results, a possible mechanism based on soft-template and self-assembly was proposed for the formation and growth of the hierarchically nanostructured HA. Cytotoxicity experiments indicated that the hierarchically nanostructured HA had good biocompatibility. It was shown by in-vitro experiments that mesenchymal stem cells could attach to the hierarchically nanostructured HA after being cultured for 48 hours.

OBJECTIVE

The purpose of this study was to develop facile and effective methods for the synthesis of novel hydroxyapatite (HA) with hierarchical nanostructures assembled from independent and discrete nanobuilding blocks.

METHODS

A simple hydrothermal approach was applied to synthesize HA by using CaCl(2), NaH(2)PO(4), and potassium sodium tartrate at 200°C for 24 hours. The cell cytotoxicity of the hierarchically nanostructured HA was tested by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.

RESULTS

HA displayed the flower-like structure assembled from nanosheets consisting of nanorod building blocks. The potassium sodium tartrate was used as a chelating ligand, inducing the formation and self-assembly of HA nanorods. The heating time and heating temperature influenced the aggregation and morphology of HA. The cell viability did not decrease with the increasing concentration of hierarchically nanostructured HA added.

CONCLUSION

A novel, simple and reliable hydrothermal route had been developed for the synthesis of hierarchically nanosized HA with flower-like structure assembled from nanosheets consisting of nanorod building blocks. The HA with the hierarchical nanostructure was formed via a soft-template assisted self-assembly mechanism. The hierarchically nanostructured HA has a good biocompatibility and essentially no in-vitro cytotoxicity.

Characterization of the chemically deposited hydroxyapatite coating on a titanium substrate

Bioactive hydroxyapatite (HA) coating on titanium (Ti) implant can be used as a drug delivery device. A controlled release of drug around the implant requires the incorporation of drug into the coating material during the coating process. HA coating was prepared using a two-step procedure in conditions suitable for simultaneous incorporation of the protein-based drug into the coating material. Monetite coating was deposited on Ti substrate in acidic condition followed by the transformation of the monetite coating to HA. X-ray diffraction (XRD) confirmed the formation of the monetite phase at the first step of the coating preparation, which was transformed into HA at the second step. Fourier transform infrared spectroscopy demonstrated typical bands of a crystallized carbonated HA with A- and B-type substitution, which was confirmed by the XRD refinement of the structural parameters. Scanning electron microscope was used to observe the morphology of monetite and HA coatings. Adhesion of the coatings was measured using a scratch tester. The critical shearing stress was found to be 84.20 ± 1.27 MPa for the monetite coating, and 44.40 ± 2.39 MPa for the HA coating.