The role of graphene oxide interlayer on corrosion barrier and bioactive properties of electrophoretically deposited ZrO2-10 at. % SiO2 composite coating on 316 L stainless steel.

In order to overcome the poor adhesion of zirconia-silica coating electrophoretically deposited on 316 L stainless steel, graphene oxide (GO) was used as an interlayer. The effect of this interlayer on morphological, microstructural, corrosion performance and bioactivity behavior of ZrO2-10 at. % SiO2 coating was studied. The zirconia-silica coating with the GO interlayer revealed a higher barrier performance as a more compact and a greater adhesive layer to the substrate was created. Indeed, the GO interlayer led to an improvement in apatite formation on zirconia-silica coating surface probably due to create higher roughness. Briefly, the GO interlayer was effective on enhancement of electrochemical performance and biological property of zirconia-silica composite coating, making it a suitable candidate for biomaterials applications.

Characterizing organic particle impacts on inert metal surfaces: Foundations for capturing organic molecules during hypervelocity transits of Enceladus plumes.

The presence and accessibility of a sub-ice-surface saline ocean at Enceladus, together with geothermal activity and a rocky core, make it a compelling location to conduct further, in-depth, astrobiological investigations to probe for organic molecules indicative of extraterrestrial life. Cryovolcanic plumes in the south polar region of Enceladus enable the use of remote in situ sampling and analysis techniques. However, efficient plume sampling and the transportation of captured organic materials to an organic analyzer present unique challenges for an Enceladus mission. A systematic study, accelerating organic ice-particle simulants into soft inert metal targets at velocities ranging 0.5-3.0 km s-1, was carried out using a light gas gun to explore the efficacy of a plume capture instrument. Capture efficiency varied for different metal targets as a function of impact velocity and particle size. Importantly, organic chemical compounds remained chemically intact in particles captured at speeds up to ~2 km s-1. Calibration plots relating the velocity, crater, and particle diameter were established to facilitate future ice-particle impact experiments where the size of individual ice particles is unknown.

Cell response to plasma electrolytic oxidation surface-modified low-modulus ß-type titanium alloys.

Plasma electrolytic oxidation (PEO) has been demonstrated to be an effective surface treatment for enhancing the osteoconduction and osseointegration of commercially pure α-Ti (CP α-Ti) dental implant materials for clinical application. To explore the feasibility of extending the application of PEO to low-modulus ß-type titanium alloys for load-bearing orthopaedic implants, a thorough understanding of the effect of substrate material on the biological performance of the PEO-treated surface is required. A 10 kW 50 Hz KeroniteTM processing unit was used to modify the surface of low-modulus near ß-Ti13Nb13Zr and ß-Ti45Nb substrates. CP α-Ti and (α + ß)-Ti6Al4V were also used in parallel as reference materials. In vitro culture of foetal human osteoblast (fHOb) cells on PEO-treated low-modulus near ß-Ti13Nb13Zr and ß-Ti45Nb alloys revealed comparable behaviour to that seen with CP α-Ti and (α + ß)-Ti6Al4V with respect to metabolic activity, collagen production, matrix formation and matrix mineralisation. No difference was observed in TNF-α and IL-10 cytokine release from CD14+ monocytes as markers of inflammatory response across samples. Cell interdigitation into the porous structure of the PEO coatings was demonstrated and cell processes remained adherent to the porous structure despite rigorous sonication. This study shows that PEO technology can be used to modify the surface of low-modulus ß-type titanium alloys with porous structure facilitating osseointegration, without impeding osteoblast activity or introducing an untoward inflammatory response.

Polyethylenimine/kappa carrageenan: Micro-arc oxidation coating for passivation of magnesium alloy.

The aim of this study was to combine micro-arc oxidation (MAO) and self-assembly technique to improve corrosion resistivity of AZ91 alloy. While a silicate-fluoride electrolyte was adopted for MAO treatment, polyethylenimine (PEI)/kappa carrageenan (KC) self-assembly coating was applied as the second coating layer. Resulted demonstrated the formation of forsterite-fluoride containing MAO coating on AZ91 alloy depending on the voltage and time of anodizing process. Addition of the second PEI/KC coating layer on MAO treated sample effectively enhanced the adhesive strength of MAO coated sample due to filling the pores with polymers and increase in the mechanical interlocking of coating to the substrate. Moreover, the corrosion evaluation considered by potentiodynamic polarization and electrochemical impedance spectroscopy confirmed that double layered PEI/KC:MAO coating presented superior resistance to corrosion attack. It is envisioned that the proposed double layered PEI/KC:MAO coating could be useful for biomedical applications.

Poly(ε-caprolactone)/nano fluoridated hydroxyapatite scaffolds for bone tissue engineering: in vitro degradation and biocompatibility study.

In this study, biodegradation and biocompatibility of novel poly(ε-caparolactone)/nano fluoridated hydroxyapatite (PCL-FHA) scaffolds were investigated. The FHA nanopowders were prepared via mechanical alloying method and had a chemical composition of Ca(10)(PO(4))(6)OH(2-x )F(x) (where x values were selected equal to 0.5 and 2.0). In order to fabricate PCL-FHA scaffolds, 10, 20, 30 and 40 wt% of the FHA were added to the PCL. The PCL-FHA scaffolds were produced by the solvent casting/particulate leaching using sodium chloride particles (with diameters of 300-500 µm) as the porogen. The phase structure, microstructure and morphology of the scaffolds were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques. Porosity of the scaffolds was measured using the Archimedes' Principle. In vitro degradation of PCL-FHA scaffolds was studied by incubating the samples in phosphate buffered saline at 37°C and pH 7.4 for 30 days. Moreover, biocompatibility was evaluated by MTT assay after seeding and culture of osteoblast-like cells on the scaffolds. Results showed that the osteoblast-like cells attached to and proliferated on PCL-FHA and increasing the porosity of the scaffolds increased the cell viability. Also, degradation rate of scaffolds were increased with increasing the fluorine content in scaffolds composition.