Bacteria are one of the significant causes of infection in the body after scaffold implantation. Effective use of nanotechnology to overcome this problem is an exciting and practical solution. Nanoparticles can cause bacterial degradation by the electrostatic interaction with receptors and cell walls. Simultaneously, the incorporation of antibacterial materials such as zinc and graphene in nanoparticles can further enhance bacterial degradation. In the present study, zinc-doped hydroxyapatite/graphene was synthesized and characterized as a nanocomposite material possessing both antibacterial and bioactive properties for bone tissue engineering. After synthesizing the zinc-doped hydroxyapatite nanoparticles using a mechanochemical process, they were composited with reduced graphene oxide. The nanoparticles and nanocomposite samples were extensively investigated by transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Their antibacterial behaviors against Escherichia coli and Staphylococcus aureus were studied. The antibacterial properties of hydroxyapatite nanoparticles were found to be improved more than 2.7 and 3.4 times after zinc doping and further compositing with graphene, respectively. In vitro cell assessment was investigated by a cell viability test and alkaline phosphatase activity using mesenchymal stem cells, and the results showed that hydroxyapatite nanoparticles in the culture medium, in addition to non-toxicity, led to enhanced proliferation of bone marrow stem cells. Furthermore, zinc doping in combination with graphene significantly increased alkaline phosphatase activity and proliferation of mesenchymal stem cells. The antibacterial activity along with cell biocompatibility/bioactivity of zinc-doped hydroxyapatite/graphene nanocomposite are the highly desirable and suitable biological properties for bone tissue engineering successfully achieved in this work.

The material for bone scaffold replacement should be biocompatible and antibacterial to prevent scaffold-associated infection. We biofunctionalized the hydroxyapatite (HA) properties by doping it with lithium (Li). The HA and 4 Li-doped HA (0.5, 1.0, 2.0, 4.0 wt.%) samples were investigated to find the most suitable Li content for both aspects. The synthesized nanoparticles, by the mechanical alloying method, were cold-pressed uniaxially and then sintered for 2 h at 1250 °C. Characterization using field-emission scanning electron microscopy (FE-SEM) revealed particle sizes in the range of 60 to 120 nm. The XRD analysis proved the formation of HA and Li-doped HA nanoparticles with crystal sizes ranging from 59 to 89 nm. The bioactivity of samples was investigated in simulated body fluid (SBF), and the growth of apatite formed on surfaces was evaluated using SEM and EDS. Cellular behavior was estimated by MG63 osteoblast-like cells. The results of apatite growth and cell analysis showed that 1.0 wt.% Li doping was optimal to maximize the bioactivity of HA. Antibacterial characteristics against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were performed by colony-forming unit (CFU) tests. The results showed that Li in the structure of HA increases its antibacterial properties. HA biofunctionalized by Li doping can be considered a suitable option for the fabrication of bone scaffolds due to its antibacterial and unique bioactivity properties.

Electrophoretic deposition of the titanium nitride (TiN) coatings from suspensions prepared by dispersion of TiN particles in triethanolamine (TEA) containing butanol medium was studied. Effects of the TiN particles concentration (C TiN ) on the weight of the deposited coatings, triethanolamine concentration (C TEA =0.25, 0.5, 0.75, and 1 mL/L) on the Zeta potential of the TiN particles, suspension electrical conductivity and pH, as well as effects of the deposition voltage (V d =60, 90, and 120 V) and time (t d =1, 2, and 3 minutes) on the microstructure and thickness of the deposited coatings were investigated. Variations in deposition current density, effective deposition voltage, electrical resistance, and deposited coating weight versus deposition time were recorded. The morphology of the as-dried coatings was studied using Scanning Electron Microscope (SEM). The results indicated that by increasing the C TiN the weight of deposits increases linearly up to 40 g/L. For suspensions containing C TiN =40 g/L, the optimum C TEA is obtained to be 0.5 mL/L leading to Zeta potential of 43.25 mV. Uniform and crack-free as-dried coatings obtained at V d and t d of 90 V and 2 minutes, respectively. K E Y W O R D Scoating, electrophoretic deposition, microstructure, sticking factor, titanium nitride

In the present study, Al 2 O 3 -Ti coated on TiAl 6 V 4 alloy used electrophoretic deposition (EPD) method to improve the corrosion resistance and biocompatibility. Electrophoretic deposition process was performed at 90 s and constant voltage of 50 V in various compositions of 30, 50, and 70 wt% of Al 2 O 3 . After deposition, samples were dried at room temperature and then the coated samples were sintered at 1050 8C for 4 h. Scanning electron microscope and X-ray diffraction analysis were employed to investigate the microstructure and phase analysis of the coatings. Moreover, the behavior of the coated samples was investigated by using electrochemical impedance spectroscopy and polarization tests. The results show that the Al 2 O 3 -Ti composite coatings sintered at an inert gas (argon) atmosphere reveals a uniform, dense coating, which includes the composition of Ti and Al oxide phases. Evaluation of electrochemical test in simulated body fluid represents the improvement of the corrosion resistance of the coated sample in comparison to uncoated TiAl 6 V 4 sample. Moreover, the 50 wt% of Al 2 O 3 composite coated sample revealed the highest corrosion resistance among the coated samples due to a uniform and more stable phase composition in comparison to other coated samples.

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