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Hydroxyapatite (HAp) nanorods, bowknot-like nanostructures and flower-like architectures have been directly synthesized and assembled under microwave irradiation without the help of any templates. The uniform nanorods present an average diameter of about 40 nm and a length of up to about 400 nm. The as-prepared bowknot-like nanostructures consist o...
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... formation of the complex sharply decreased the free Ca 2+ concentration in the solution, and effectively prevented the formation of ACP upon mixing sources of Ca and P in the presence of EDTA [24]. Figure 6 presents the molecular structure of the Ca-EDTA complex. In the complex, EDTA acts as a hexadentate unit by wrapping itself around the metal ion with four oxygen atoms and two nitrogen atoms and forms several five-member chelate rings. ...
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... However, the solution B contains a large amount of free Al 3+ ions in this experiment, which results in continuous complexation of EDTA. Moreover, Y 4− is dominant in the form of EDTA in solution when the pH is more than 10 [30,46,47]. And its complexation with Mg 2+ ions and Al 3+ ions are as follows: ...
... The synthesis procedure of NFHA using microwave irradiation was modified from a method reported by Liu et al. 66 Briefly, 50 mL of 0.08 M Ca(NO 3 ) 2 .4H 2 O and 50 mL of 0.08 M EDTA solutions were prepared SBF and mixed for a 15 min. Then 50 mL 0.048 M of (NH 4 ) 2 HPO 4 phosphate solution is slowly added to the Ca-EDTA mixture. ...
To investigate the reinforcing effect of nanoflower‐like hydroxyapatite (NFHA) in resin‐based dental composites, we synthesized a novel NFHA using microwave irradiation (MW), hydrothermal treatment (HT), and sonochemical synthesis (SS). Silanized NFHA was then used as the reinforcing filler in dental resin composites. We characterized the structure and morphology of various HA nanostructures using x‐ray diffraction, scanning electron microscope, and TEM. The mechanical performance of dental resin composites reinforced with silanized NFHA was measured using a universal testing machine. Spherical HA, synthesized through chemical precipitation (CP), served as the control group. One‐way analysis of variance was employed for the statistical analysis of the acquired data. The results demonstrate that the nanoflower morphology significantly was improved mechanical and physical properties. After conducting trials, the NFHA synthesized using MW and HT showed a substantial enhancement in mechanical and physical properties compared to the other structures. Therefore, it can be concluded that NFHA can serve as a novel reinforcing HA filler, providing regenerative properties to resin composites with sufficient mechanical strength.
... Zhu's team, inspired by the structure characteristic of sea-urchin and the fact that hydroxyapatite is the main component of tooth, 153 synthesized the hydroxyapatite particle with 3D urchinlike whiskers (UHA) spherical structure by microwave-assisted irradiation method (Fig. 6b), and then used them as the reinforcement filler in DRCs. 143,154 The results showed that this urchin-like whiskers filler, presenting a hierarchical spherical structure with a particle size of 2-3 μm, has good dispersion in the resin matrix and the whiskers could embed into the resin matrix in multiple directions, which can form the micromechanical interlocking interface between filler and resin matrix and thus improve the properties of the corresponding composites. This structure combined the enhancement effect of one-dimensional whiskers and interface micromechanical interlocking structure, which therefore more effectively resisted the relative displacement of fillers and optimized the properties of DRCs. ...
Dental resin composites (DRCs) are popular materials for repairing caries or dental defect, requiring excellent properties to cope with the complex oral environment. Filler/resin interface interaction has a significant impact on the physicochemical/biological properties and service life of DRCs. Various chemical and physical modification methods on filler/resin interface have been introduced and studied, and the physical micromechanical interlocking caused by the modification of fillers morphology and structure is a promising method. This paper firstly introduces the composition and development of DRCs, then reviews the chemical and physical modification methods of the filler/resin interface, mainly discusses the interface micromechanical interlocking structures and their enhancement mechanism for DRCs, finally give a summary on the existing problems and development potential.
... In parallel, the designed resonant cavity provides regions of uniform electric field and therefore this device can be used to irradiate different types of materials. For example, the processes reported in [60,61], could be scaled up due to the selective radiation of the structures. ...
Irradiation of multi-wall carbon nanotubes (MWCNT) was performed at different energy densities to characterize structural changes induced by a highly localized 2.45 GHz electric field. For this purpose, a transversal electric (TE102) resonant microwave cavity was designed and coupled to a standard 800 W microwave oven magnetron. The nanotubes were sealed inside a Pyrex reactor at 10⁻⁴ Torr to avoid oxidation or reactions with the environment. Irradiated MWCNT properties were characterized using Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, Thermogravimetry, Solubility tests and Transmission Electron Microscopy. In this work, the energy densities required to modify the MWCNT structure were obtained through an optical method. From an energy density of 82 J/cm³, nanotubes presented nondestructive structural changes, loss of catalytic particles and a decrease of amorphous carbon structures on the surface. A more effective modification with high purity and clearly better structured walls was observed for 167 J/cm³. Furthermore, it was determined that at an energy density of 6.9 KJ/mol a higher purification of MWCNTs is obtained. This value is in agreement with the enthalpy of formation reported for the MWCNTs. This experimental approach could be applied for the functionalization of carbon nanostructures. Finally, the purification process is easily scalable, environmentally friendly and makes maximum use of the irradiated energy.
... EDTA as disodium salt can mask calcium cations, thus preventing them from directly reacting with phosphate anions. 27,28 The process can be simply summarized by eq 1: ...
Developing appropriate protecting coatings for Mg alloy applications is a challenging issue. Herein, nanohydroxyapatite (nanoHAP) powder was first fabricated by the simple hydrothermal microwave-assisted method. A direct current electrophoresis deposition (EPD) of nanoHAP composite coatings on Mg–3Zn–0.8Ca magnesium alloy was successfully executed. Three suspensions with HAP-dispersive resin solution (ETELAC) ratios (in wt %) of 5–5, 5–2.5, and 2.5–2.5 were chosen for optimizing the effect of applied voltage, deposition time, and stirring mode and rates on the EPD process. NanoHAP composite coatings were applied on each sample in single- and double-run depositions. The results revealed that the maximum weight gain on the coated samples was obtained in 5–5 suspension at 50 V under 150 rpm mechanical stirring rate. Surface examination indicated crack-free coating formation with varying grain sizes. Adhesion tests demonstrated high interconnection between the obtained nanocomposite coatings and the alloy substrate. Electrochemical evaluation measurements in SBF at 37 °C indicated that the corrosion resistance of any coated sample is always superior compared to that of the uncoated bare substrate. It was suggested that the EPD of nanoHAP/ETELAC composite coatings on Mg–Zn–Ca alloy can be a good solution for protecting the alloy from the attack of the aggressive ions bound in the SBF environment.
... EDTA diminishes Ca 2+ reactivity, slows the rate of crystal nucleation and mediates crystal growth. The strength of chelation is dependent upon pH; EDTA is a stronger chelator of Ca 2+ at higher pH [78]. ...
... Ca 2+ gradually dissociates from the EDTA-Ca complexes and displays preferential binding to the crystal's polar (001) direction [71]. Diffusion-limited growth leads to the formation of single nanorods from each nucleate and the formation of spear-like crystals with one sharp end [78]. Van der Waals attraction along the crystal long axis causes HA nanorods to aggregate and align in parallel leading to bundle formation. ...
The distinct architecture of native enamel gives it its exquisite appearance and excellent intrinsic-extrinsic fracture toughening properties. However, damage to the enamel is irreversible. At present, the clinical treatment for enamel lesion is an invasive method; besides, its limitations, caused by the chemical and physical difference between restorative materials and dental hard tissue, makes the restorative effects far from ideal. With more investigations on the mechanism of amelogenesis, biomimetic mineralization techniques for enamel regeneration have been well developed, which hold great promise as a non-invasive strategy for enamel restoration. This review disclosed the chemical and physical mechanism of amelogenesis; meanwhile, it overviewed and summarized studies involving the regeneration of enamel microstructure in cell-free biomineralization approaches, which could bring new prospects for resolving the challenges in enamel regeneration.
... The organic modifiers such as EDTA, PEG and TSC interact with calcium ions to make complex forms. The polyamino carboxylic acid of EDTA (hexadentate unit) reacts with Ca 2+ to form a Ca-EDTA complex [45], PEG is a weak chelating and non-ionic organic modifier and chelate the Ca 2+ ions in the form of PEG-O-Ca 2+ -O-PEG [46], while citrate ion reacts with Ca 2+ ions to form calcium citrate complex [36]. These complexes reduce the availability of free Ca 2+ ions and inhibit the formation of HA at ambient temperature. ...
... Under microwave irradiation or thermal impact, the reaction mixture containing calcium complex releases Ca 2+ ions which immediately react with phosphate and phosphate complex releases PO 4 3− ions which abruptly react with calcium to form HA crystal with controlled size and shape. The mechanism of formation of flower like HA in presence of EDTA was previously reported by several researchers [45,48,49]. Jung Sang Cho et al., reported the spherical, rod and fibre like HA nanoparticles formed in presence of different concentration of PEG organic modifiers [50]. ...
... The organic modifiers such as EDTA, PEG and TSC interact with calcium ions to make complex forms. The polyamino carboxylic acid of EDTA (hexadentate unit) reacts with Ca 2+ to form a Ca-EDTA complex [45], PEG is a weak chelating and non-ionic organic modifier and chelate the Ca 2+ ions in the form of PEG-O-Ca 2+ -O-PEG [46], while citrate ion reacts with Ca 2+ ions to form calcium citrate complex [36]. These complexes reduce the availability of free Ca 2+ ions and inhibit the formation of HA at ambient temperature. ...
... Under microwave irradiation or thermal impact, the reaction mixture containing calcium complex releases Ca 2+ ions which immediately react with phosphate and phosphate complex releases PO 4 3− ions which abruptly react with calcium to form HA crystal with controlled size and shape. The mechanism of formation of flower like HA in presence of EDTA was previously reported by several researchers [45,48,49]. Jung Sang Cho et al., reported the spherical, rod and fibre like HA nanoparticles formed in presence of different concentration of PEG organic modifiers [50]. ...
Utilizing eggshells to synthesize a value added product like nanocrystalline hydroxyapatite (HA) has received a lot of attention from researchers since they are composed of CaCO3 with biologically essential trace elements such as Mg, Si, etc. Different biomedical applications need HA with appropriate nanoscale characteristics like crystallinity, particle size, morphology, surface area, mesoporous nature, etc. The same can be achieved by tuning the reaction parameters, choosing a suitable mode of preparation and utilizing organic modifiers. Here, we report the rapid synthesis of eggshell derived HA in the presence different organic modifiers using a custom built microwave reactor employing the previously optimized parameters. The synthesis process is relatively rapid and gets completed in 5 min. The absence of an organic modifier yielded inhomogeneous size nanorods in the range of 40 – 600 nm. Ethylenediaminetetraacetic acid (EDTA) assisted synthesis resulted in a flower like 1.67 ± 0.12 μm sized HA. Whereas polyethylene glycol 6000 (PEG) and cetyltrimethylammonium bromide (CTAB) assisted synthesis produced aggregated nanorods of length 31 ± 8 and 68 ± 20 nm, respectively. While the synthesis with trisodium citrate dihydrate (TSC) resulted in needles of HA with typical length of 32 ± 8 nm. Presence of Na, Mg and Si trace elements are confirmed from the composition analysis. All the samples are found to be mesoporous in nature. The in vitro cell culture experiment carried out using fibroblast NIH 3T3 cell line clearly revealed equal or higher cell viability for the samples synthesized in presence of organic modifiers as compared to sample produced without organic modifier. Thus, from the present study we find that the synthesis of eggshell derived HA using different organic modifiers via a custom built microwave reactor can be a potential approach for the rapid preparation of precursor materials with suitable nanoscale characteristics for developing bone fillers, drug/protein delivery carriers, tissue engineering scaffolds, etc.
... It should, however, be noted that the P extraction efficiency in an alkaline environment increased considerably in the presence of chelating agents, except for the SSA (see Fig. 2). This might be due to the fact that chelating agents such as EDTA and NTA can form highly soluble complexes with the phosphate counter ions such as Al, Ca, Fe and Mg [47][48][49]. Hence, strong complex formation with for instance Ca will shift the Ca-phosphate dissolution reaction to the right, even if Ca-phosphates as such are poorly soluble in an alkaline environment. The latter is discussed in more detail in the last paragraph of section 'P Extraction by Alkaline Extraction Liquid and Chelating Agents'. ...
... Second, as for the PMA and MBMA, it was expected that phosphates in the SSA can dissolve through complex formation of chelating agents with the phosphate counter ion. However, the stability of EDTA and NTA complexes deteriorates with decreasing pH [49,51,52]. Hence, the complexes for the PMA and MBMA extraction were more stable than for the SSA extraction because of the higher pH at the end of the EDTA and NTA extraction procedure (11.9-12.2 for PMA and MBMA, and 9.9 for SSA, respectively). ...
... Hence, the complexes for the PMA and MBMA extraction were more stable than for the SSA extraction because of the higher pH at the end of the EDTA and NTA extraction procedure (11.9-12.2 for PMA and MBMA, and 9.9 for SSA, respectively). Indeed, the fraction of EDTA and NTA present in its fully deprotonated form, at which the metal complexes are most stable, depends on the pH of the solution [49,51,52]. For instance, at pH 10 only 37% of the EDTA is present in its fully deprotonated form, whereas this is almost 100% at pH 12 [51]. ...
Phosphorus (P) rich ash from biomass incineration is a potential promising alternative for non-renewable phosphate rock. This study considered the P recovery potential of poultry manure ash, sewage sludge ash and meat and bone meal ash through wet chemical extraction. X-ray diffraction analysis showed that these three ash types had a distinct P mineralogy. If inorganic acids were used for the extraction, the P extraction efficiency was not or only slightly affected by the P mineralogy. Contrarily, for the organic acids, alkaline extraction liquid and chelating agents considered, the P extraction efficiency was highly affected by the P mineralogy, and was also affected by the elemental composition of the ash and/or the chemical characteristics of the extraction liquids. Alkaline extraction liquids showed in general low heavy metal co-extraction, in contrast to the inorganic acids. From an economic point of view, of all extraction liquids considered, sulfuric acid was the most interesting to extract P from all three ash types. Oxalic acid could be a more sustainable option for P extraction from sewage sludge ash. In addition, extraction of poultry manure ash with ethylenediaminetetraacetic acid showed a relatively high P extraction efficiency combined with relatively low heavy metal co-extraction.
Graphic Abstract
... The surface morphology of HAp is mainly dependent on the physicochemical environment such as stoichiometry, rate of addition, pH, temperature, ionic strength, synthesis methods, and therefore, these parameters must be controlled. At an average temperature, the most stable form of calcium phosphate is HAp; in the pH range of 4-12 with Ca/P molar fraction 1.67 to maintain its stoichiometry significantly [31,32,35]. ...
Nowadays researchers are much interested in bioceramics for their use as biological implants. Researchers have succeeded to derive few bioceramic materials which show good biological response with living tissues. Few of the bioceramics are zirconia, hexagonal boron nitride and hydroxyapatite. Herein, the effects of zirconia nanoparticles and hexagonal boron nitride nanosheets in hydroxyapatite powder on the structural, mechanical, and biological properties were investigated. In this study, the formation of a potential composite with desired mechanical and biological properties is strongly anticipated. The present study is also proposed to provide further faces to improve osteogenic properties of the scaffolding material without altering the established mechanical and biological properties. Three different compositions in the system [(95-x)HAp-x(ZrO2)-5hBN] (x = 10, 20, 30) were prepared using a simple solid-state reaction technique. In the samples, significant phase was identified for HAp [Calcium Phosphate Hydroxide: Ca5(PO4)3(OH)]. SEM analysis of the composites revealed well-connected and uniform distribution of ZrO2 and HAp nanoparticles on h-BN sheets. The composite samples 65H30Z5B9h (65HAp-30ZrO2-5hBN sintered at 900 °C) and 65H30Z5B1T (65HAp-30ZrO2-5hBN sintered at 1000 °C) showed improved mechanical and tribological behaviors. These samples exhibited excellent mechanical properties like compressive strength, Young's modulus, toughness and density. The obtained values were 2.154 MPa, 0.0182 MPa, 553.82 MJ/m³, 2.29 g/cm³ for 65H30Z5B9h and 3.798 MPa, 0.0832 MPa, 231.59 MJ/m³, 2.31 g/cm³ for 65H30Z5B1T respectively. Cytotoxicity of the composites was studied on Drosophila fly and Mice calvarial osteoblasts cells at five different concentrations. Toxic effect of the composite 65H30Z5B1T on the fly was confirmed by phenotypic observations, trypan blue staining, pupal count, and larval crawling speed. Composite 65H30Z5B1T was found to be toxic in this study, but the composite 65H30Z5B9h was not. Further, cell viability, alkaline phosphates, and mineralization tests confirmed non-toxic property and enhanced osteogenic activities for the composite sample 65H30Z5B9h.
