Hydroxyapatite (HAP) is the naturally occurring mineral form of calcium apatite and the most studied material as a bone substituent. Considering HAP's inherent properties, this study explored changes ...in HAP's characteristics from doping with other metals such as Fe. To form pure HAP and Fe-HAP with different amounts of Fe, we used the hydrothermal approach, and the composites that formed were thoroughly analyzed for their crystallinity, surface bonding, morphology, magnetic behavior, mechanical strength, biocompatibility, hemocompatibility, and in vitro cytotoxicity. The powder XRD studies confirmed the samples' crystallinity, and the lowest crystalline size was 19.7 nm in 10Fe-HAP. The FTIR analysis confirmed the formation of HAP by the hydroxyl, phosphate, and carbonate groups. The FESEM demonstrated that the morphology of the pure HAP was rod-shaped, which transformed into spheres after Fe doping. The EDS analysis confirmed the successful formation of HAP and Fe-HAP composites. The magnetic studies indicated the diamagnetic behavior of the pure HAP, while the Fe-doped HAPs had a superparamagnetic nature with saturation magnetizations (Ms) of 2Fe-HAP, 4Fe-HAP, and 10Fe-HAP at 0.0062, 0.0092, and 0.029 emu/g respectively. Assessment of the mechanical properties, biocompatibility, hemocompatibility, and cytotoxicity indicated that the Fe-doped HAPs were superior to the pure HAP, and among the Fe-HAPs, the 10Fe-HAP) had the highest amount of Fe and the best characteristics. The studies also indicated that Ca2+ interactions influenced the cells via HAP doping with that of Fe, equally increasing the physicochemical and biological properties.
Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is the main constituent mineral of bone and teeth in mammals. Due to its outstanding biocompatibility and osteoconductive capabilities, it is preferred for bone ...repair and replacement. Owing to high potential to have excellent biological properties, ternary ions-doped HAs have just begun to be investigated in the biomedical field and preparing multi-doped HAs is a fairly new approach. Boron (B, BO33-), strontium (Sr, Sr2+) and magnesium (Mg, Mg2+) provide a beneficial effect on bone growth, bone strength, biocompatibility and positively affect bone microstructure. The motivation of this study is taking advantages of the potential of the combine effects of these bivalent ions. In this study, 8 different compositions of BO33-, Sr2+, Mg2+ multi-doped HAs were synthesized by microwave irradiation method to investigate the structural, mechanical and biological features of bone substitutes. This is the first time we report the effect of boron, strontium and magnesium ions multi-doping on the structure of HA and its biological properties. Samples were sintered at 700, 900 and 1100 °C. The effect of varying ion contents and sintering temperature on structural and biological properties of the multi-doped samples was investigated. B, Sr and Mg ions were successfully doped into the HA structure according to X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analyses. A biphasic structure was obtained with increasing amount of ion-doping. Increasing the sintering temperature affected the crystallinity and the density of the samples gradually. Vicker's microhardness and diametral strength of the samples increased at high sintering temperatures. B–Sr–Mg multi-doped HA promoted osteoblast-like Saos-2 cell proliferation, and as the sintering temperatures of the samples increased, the osteogenic differentiation level of the cultured cells also increased. Overall, results showed that the biological properties of HA were improved with the doping of Sr, Mg and B ions, and for bone implant applications samples sintered at 1100 °C were suggested to have potential as a biomaterial.
•BO33-, Sr2+ and Mg2+ multi-doped hydroxyapatites(HA) were successfully synthesized.•Synthesized pure and multi-doped HAs were sintered at 700, 900 and 1100 °C.•Depending on doping amount, biphasic structure (HA and β-TCP) was obtained.•BO33-, Sr2+ and Mg2+ multi-doped HAs promoted osteoblast-like Saos-2 cell proliferation.•The osteogenic differentiation level of the cultured cells on multi-doped HAs increased.
A novel amidoxime-functionalized magnetic hydroxyapatite (AFNH) was successfuly fabricated to extract uranium from aqueous solution and seawater. The introduction of amidoxime group not only ...increased the number of active site of AFNH to speed up the adsorption rate and increase the extraction capacity, but also adjusted the optimal extraction pH from 4 to 8, which was beneficial for capturing uranium from seawater. The maximum adsorption capacity and adsorption efficiency at pH 8 were 945.2 mg g−1 and 99.2%, respectively. AFNH still had good removal efficiency (above 90%) after five cycles, indicating the good regeneration of AFNH. After uranium adsorption, AFNH could be easily recycled by magnetic separation due to its magnetism. In simulated seawater, AFNH also showed excellent uranium removal performance with high adsorption efficiency (84.9%) and adsorption capacity (1.70 mg g−1). Furthermore, the 14-day uranium extraction capacity of AFNH in natural seawater could reach 5.93 mg g−1. The SEM, FTIR, XRD and XPS analyses showed that the enhanced uranium extraction performance of AFNH was mainly attributed to electrostatic interaction, complexation and co-precipitation. In conclusion, AFNH was expected to be a candidate as adsorbent with great potential in extracting uranium from seawater.
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•A novel amidoxime-functionalized magnetic hydroxyapatite (AFNH) was successfully designed.•AFNH possessed excellent uranium extraction performance in alkaline conditions.•The removal efficiency of AFNH was still higher than 90% after five cycles.•Electrostatic interaction, complexation and co-precipitation were the main mechanisms of AFNH.
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•Polydopamine (PDA) functionalized ultrathin hydroxyapatite (HAp) nanosheets were prepared by self-polymerization of dopamine on HAp surface.•PDA@HAp nanosheets exhibit better ...dispersion performance than HAp nanosheets in epoxy resin.•PDA@HAp nanosheets can provide physical barrier effect and corrosion inhibition in the coatings, leading to better anti-corrosion properties during long-time immersion.
It is known that two-dimensional nanosheets such as graphene, hexagonal boron nitride and layered double hydroxide can provide organic coatings with enhanced anticorrosion performance due to the high aspect ratio and excellent barrier property. As a kind of biocompatible material, the corrosion resistance of hydroxyapatite (HAp) in the biological body leads to its wide application. In this work, ultrathin HAp nanosheets were noncovalently functionalized by situ self-polymerization of dopamine chemistry with an aim to improve their compatibility and dispersibility in epoxy matrix. Electrochemical impedance spectroscopy (EIS) illustrated composited coating exhibited a higher value of impedance at low frequency compared to pure epoxy coating after 50 days of immersion in 3.5 wt% NaCl solution. Local electrochemical impedance spectroscopy (LEIS), spray tests and corrosion products characterization were also carried out to evidence that the modified HAp nanosheets could significantly improve the anti-corrosion performance of epoxy coatings via the enhanced barrier property and corrosion inhibiting effect of polydopamine, which is expected to be widely applied as nano-reinforcing fillers in the anticorrosion field.
The effectiveness and mechanism of nano-hydroxyapatite particles (nHAp) in immobilizing Pb and Cd from aqueous solutions and contaminated sediment were investigated. The maximum sorption amount (
Q
...max) of Pb and Cd in aqueous solution was 1.17 and 0.57 mmol/g. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) surface and depth analysis indicated that dissolution-precipitation is the primary immobilization mechanism for Pb, while surface complexation and intraparticle diffusion account for Cd sequestration. Different amounts of nHAp (0–10% nHAp/dry weight) were added to the contaminated sediment. Sequential extraction showed that nHAp could effectively reduce the exchangeable fraction of Pb and Cd in the sediment and significantly reduce the concentration in porewater. The results in this study showed that nHAp can immobilize Pb and Cd in sediment effectively.
Nano-hydroxyapatite shows potential and advantages to immobilize lead and cadmium in aqueous solution and sediment.
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