Biodegradable Mg/HA/TiO2 Nanocomposites Coated with MgO and Si/MgO for Orthopedic Applications: A Study on the Corrosion, Surface Characterization, and Biocompatability

In the field of orthopedics, magnesium (Mg) and magnesium-based composites as biodegradable materials have attracted fundamental research. However, the medical applications of magnesium implants have been restricted owing to their poor corrosion resistance, especially in the physiological environment. To improve the corrosion resistance of Mg/HA/TiO2 nanocomposites, monolayer MgO and double-layer Si/MgO coatings were fabricated layer-by-layer on the surface of a nanocomposite using a powder metallurgy route. Then, coating thickness, surface morphology, and chemical composition were determined, and the corrosion behavior of the uncoated and coated samples was evaluated. Field-emission scanning electron microscopy (FE-SEM) micrographs show that an inner MgO layer with a porous microstructure and thickness of around 34 m is generated on the Mg/HA/TiO2 nanocomposite substrate, and that the outer Si layer thickness is obtained at around 23 m for the double-layered coated sample. Electrochemical corrosion tests and immersion corrosion tests were carried out on the uncoated and coated samples and the Si/MgO-coated nanocomposite showed significantly improved corrosion resistance compared with uncoated Mg/HA/TiO2 in simulated body fluid (SBF). Corrosion products comprising Mg(OH)(2), HA, Ca-3(PO4)(2), and amorphous CaP components were precipitated on the immersed samples. Improved cytocompatibility was observed with coating as the cell viability ranged from 73% in uncoated to 88% for Si/MgO-coated Mg/HA/TiO2 nanocomposite after nine days of incubation

The effect of MgO on the biodegradation, physical properties and biocompatibility of a Mg/HA/MgO nanocomposite manufactured by powder metallurgy method

Recently, magnesium-hydroxyapatite composites have shown the potential to serve as biodegradable metal matrix composite implants that can repair load-bearing defects in osseous tissue. However, the mechanical properties and corrosion resistance of magnesium-hydroxyapatite composites have been restricted by the significant agglomeration of HA particulates. In this study, the bio-corrosion properties of a Mg/HA-based composite were improved by the addition of different amounts of hydroxyapatite (HA) and periclase (MgO) nanopowders to pure magnesium and fabrication of the Mg/HA/MgO nanocomposites using a blend-cold press-sinter powder metallurgy (PM) technique. X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, atomic force microscopy and field-emission scanning electron microscopy were used to characterize the compositions of the corrosion products and the surface morphologies of the corroded specimens. Based on the electrochemical test, the corrosion resistance of the nanocomposites is shown to increase from 0.25 kΩ cm2 to 1.23 kΩ cm2 with the addition of 10 wt% MgO; however, the ultimate compressive strength decreased from ∼237 to ∼198 MPa. During immersion test in SBF solution, the growth of the Mg(OH)2 nanorods on the Mg-12.5HA-10MgO and Mg-5HA-15MgO (wt%) nanocomposites increased the contact angle between the SBF solution and the substrate; as a result, the corrosion rate decreased compared to that of the Mg-27.5HA-10MgO and Mg-20HA-5MgO (wt%) nanocomposites. The corrosion products formed on the nanocomposites surface are shown to be primarily Mg(OH)2, HA, Ca3(PO4)2 and amorphous CaP compounds. The cell culture results indicated that the Mg/HA/MgO nanocomposites remained biocompatible with osteoblasts by increasing of MgO amoun

Fabrication, bio-corrosion behavior and mechanical properties of a Mg/HA/MgO nanocomposite for biomedical applications

The Mg/HA/MgO nanocomposites were fabricated with pure magnesium and the addition of different amounts of hydroxyapatite and periclase nanopowders using a blend-cold press-sinter powder metallurgy technique to improve the bio-corrosion and mechanical properties of the resulting material. Potentiodynamic polarization, immersion and mechanical tests were used to investigate bio-corrosion and mechanical properties of the nanocomposites produced. The compositions of the corrosion products and surface morphologies of the corroded specimens were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and field-emission scanning electron microscopy. The corrosion resistance of the nanocomposites is shown to increase from 0.25kOcm2 to 1.23kOcm2 with the addition of 10wt.% MgO; additionally, decreasing the amount of HA from 27.5 to 12.5wt.% is shown to yield an increase in the compressive failure strain from 4.2 to 11.5%. The corrosion products of the composite surface are shown to be primarily Mg(OH)2, HA and Ca3(PO4)2. During immersion in SBF solution, the growth of the Mg(OH)2 nanorods on the nanocomposites increased the contact angle between the SBF solution and the substrate; as a result, the corrosion rate and hydrogen evolution rate decreased. The cell culture results indicate that Mg/HA/MgO nanocomposite is biocompatible with osteoblasts

Microstructural characterization, biocorrosion evaluation and mechanical properties of nanostructured ZnO and Si/ZnO coated Mg/HA/TiO2/MgO nanocomposites

Nano-ZnO monolayer and nano-Si/ZnO double-layer coatings were deposited on a Mg/HA/TiO2/MgO nanocomposite using radio frequency magnetron sputtering. The composition and surface morphology of the specimens were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy and field-emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. Potentiodynamic polarization and immersion tests were used to investigate the corrosion behavior of samples. The Si/ZnO nanocomposite coating, which had an average thickness of 1.7µm, exhibited a uniform and dense film, consisting of a ZnO outer layer (~1.1µm thick) and a Si inner layer (~0.6µm thick). However, some pores and cracks were observed in the ZnO monolayer coating (~1.5µm thick). In addition, the Si and ZnO nanoparticles had a spherical morphology with an average particle size of 28-40nm. Higher polarization resistance values were obtained for the nano-Si/ZnO coated sample (~2.55kOcm2) compared with that of the ZnO coated (~1.34kOcm2) and uncoated (~0.14kOcm2) samples in a simulated body fluid (SBF). The results from the hydrogen evolution studies indicated that the nano-Si/ZnO-coated sample had a lower degradation rate (1.07ml/cm2/day) than the ZnO-only coated sample (2.25ml/cm2/day) and the uncoated sample (4.42ml/cm2/day). After 168h of immersion in a SBF solution, a larger amount of hydroxyapatite precipitated on the Si/ZnO coating than the ZnO coating, which resulted in an improvement in the bioactivity. The compressive strength and elongation of uncoated Mg/HA/TiO2/MgO decreased from 253MPa and 9.8% to 104MPa and 5.2% after 28days of immersion in SBF solution, whereas the Si/ZnO coated sample indicated a compressive strength of 148MPa and elongation of 7.2%. Therefore, the double-layer Si/ZnO composite coating prepared by magnetron sputtering on the Mg/HA/TiO2/MgO nanocomposite is more suitable for biomedical applications

Facile fabrication of hydrophobic surfaces on mechanically alloyed-Mg/HA/TiO2/MgO bionanocomposites

The effect of mechanical alloying and post-annealing on the phase evolution, microstructure, wettability and thermal stability of Mg-HA-TiO2-MgO composites was investigated in this study. Phase evolution and microstructure analysis were performed using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy, as well as the wettability determined by contact angle measurements with SBF. The 16-h mechanical alloying resulted in the formation of MgTiO3, CaTiO3, Mg3(PO4)2 and Mg(OH)2 phases and a decrease in wettability of the nanocomposites. A hydrophobic film with hierarchical structures comprising nanoflakes of MgTiO3, nano-cuboids of CaTiO3, microspheres of Mg3(PO4)2 and Mg(OH)2 was successfully constructed on the surface of the Mg-based nanocomposites substrates as a result of the post-annealing process. After 1-h annealing at 630 °C, the synthesized hydrophobic surface on the nanocomposite substrates decreased the wettability, as the 8-h-mechanically alloyed samples exhibited a contact angle close to 93°. The formation activation energies and reaction kinetics of the powder mixture were investigated using differential thermal analysis and thermal gravimetric analysis. The released heat, weight loss percentage and reaction kinetics increased, while the formation activation energies of the exothermic reactions decreased following an increase in the milling tim

Synthesis, microstructure and biodegradation behavior of nano-Si and nano-ZnO/Si coatings on a Mg/HA/TiO2/MgO nanocomposite

In this study, a successful synthesis of nano-Si single-layer and nano-ZnO/Si double-layer coatings on Mg/HA/TiO2/MgO nanocomposite using radio frequency magnetron sputtering was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The double-layered ZnO/Si nano-composite coating consisted of ZnO nanospheres with an average particle size of 28 nm as the outer layer (~0.6-µm-thick, sputtering pressure of 0.16 Pa) and the columnar microstructure of Si with an average particle size of 32 nm in length and 21 nm in width as the inner layer (~1.1-µm-thick, sputtering pressure of 0.24 Pa). Microstructural analysis reveals little surface damage after ZnO/Si coatings initially and after 168 h immersion in simulated body fluid, corrosion protective products including Mg(OH)2, Ca10(PO4)6(OH)2 and carbonate ions are formed on the uncoated and coated samples. A significant increase in the corrosion resistance (~2.55 kO cm2) of the nano-ZnO/Si-coated sample was observed in simulated body fluid compared to the Si-only coated samples (~2.17 kO cm2) and the uncoated samples (~0.14 kO cm2). Hydrogen evolution studies showed that the nano-ZnO/Si-coated sample (1.07 ml/cm2/day) had a lower degradation rate than the Si-only coated sample (2.17 ml/cm2/day) and uncoated sample (4.42 ml/cm2/day)

In vitro biocorrosion, antibacterial and mechanical properties of silicon-containing coatings on the magnesium-hydroxiapatite nanocomposite for implant applications

In this study, to control the rapid degradation rate of Mg/27.5HA nanocomposite, the single-layered Si and double-layered MgO/Si coatings were fabricated on Mg/27.5HA by milling-multi steps pressing-sintering powder metallurgy method. The microstructure, chemical composition and cross-section of the coatings as well as the corrosion products were characterized using FE-SEM, XRD, FT-IR and TEM. The degradation behavior of uncoated, Si- and MgO/Si-coated nanocomposites was examined by impedance measurements, potentiodynamic polarization and weight loss tests. The corrosion resistance of Mg/27.5HA was significantly improved by double-layer MgO/Si coating resulted in the lower corrosion current; 7.9 mA/cm 2 versus 187.4 mA/cm 2 for the uncoated sample, as well as the higher corrosion potential; −1292.3 versus −1487.3 mVSCE. In addition, immersion tests indicate the decrease in weight loss rate of Si-coated and MgO/Si-coated Mg/27.5HA nanocomposites compared to the uncoated sample. After 28 days of immersion in SBF, much less degradation rates of the Si- and MgO/Si-coated nanocomposites led to the slower losses of the mechanical properties. Antibacterial tests on the bare and coated samples consisting MgO revealed the antibacterial activity against Staphylococcus aureus and Escherichia coli. Moreover, according to the in vitro cell culture test, a significant enhancement in the biocompatibility was obtained for Mg/27.5HA nanocomposite with Si-containing coatings

A comparative study of nanocrystalline SiC thin films on multimode optical fiber sensors, synthesized via DBD-NTP and 150 MHz VHF-PECVD

In this study, nanocrystalline SiC films were successfully synthesized on the surface of multimode fiber (MMF) sensors using 150 MHz very-high-frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) and dielectric barrier discharge nonthermal plasma (DBD-NTP) methods. The effects of the different utilized methods and various deposition times on the microstructure and chemical composition of the deposited SiC films were investigated For both methods, the SiC film thickness increased with increased deposition time. The dependency of sensitivity on the deposition time and thickness of SiC films was studied by investigating the effects of refractive index and temperature variation on the response of the MMF sensors. The SiC films deposited by 150 MHz VHF-PECVD showed more uniformity and higher sensitivity compared to those deposited using DBD-NTP. Using VHF-PECVD with a deposition time of 1 min yielded the lowest thickness (54.06 nm) and therefore the highest sensitivity (0.0240 dB/°C) for the SiC-deposited MMF sensors. Thus, the VHF-PECVD method may be a better option than DBD-NTP for the deposition of thin SiC films to improve the sensitivity of the MMF sensors