New fabrication method for producing reduced graphene oxide flexible electrodes by using a low-power visible laser diode engraving system.

The fabrication of bendable electronic devices is a scientific-technological area of very rapid advance in which new materials and fabrication techniques are being continuously developed. In these kinds of devices, the fabrication of flexible conductive electrodes adherent to the substrate is a key factor. Further, eco-friendliness, low cost and fast production are essential requirements for the successful progress of new technologies. In this work, a novel method for obtaining graphene-based flexible electrodes is presented. Conductive films were obtained by means of the visible laser irradiation of graphene oxide layers deposited on polyethylene terephthalate substrates and self-standing membranes sandwiched between glass slides. Despite the low power of the laser system, the numerical simulations indicate the development of temperatures over 1000 K throughout the irradiated material. The laser-induced spatially confined heating leads to the reduction of the graphene oxide material, whereas the glass-based sandwich assembly avoids reoxidation from the surrounding air. By scanning and pixelated modes, reduced graphene oxide electrodes, up to 100 µm in thickness, and with a resistivity as low as 6 × 10-4 Ωm, were obtained in an easy and versatile way. Proof-of-concept microsupercapacitors and electrochemical sensors were fabricated with this technique, showing promising performance.

Fish and omega-3 fatty acid intake in relation to circulating fibroblast growth factor 23 levels in renal transplant recipients.

BACKGROUND AND AIMS: A high circulating fibroblast growth factor 23 (FGF23) level is an independent risk factor for cardiovascular mortality in renal transplant recipients and the general population. N-3 fatty acids eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) may contribute to cardiovascular risk reduction. We investigated whether fish and EPA-DHA intake are related to FGF23 levels in renal transplant recipients. METHODS AND RESULTS: We performed a cross-sectional analysis in 619 stable renal transplant recipients (mean age 53 years, 57% male, estimated glomerular filtration rate [eGFR] 53 ± 20 mL/min/1.73 m(2)). Dietary intake was assessed by a 177-item food frequency questionnaire. Serum intact FGF23 was measured by ELISA. We examined differences in FGF23 levels across categories of fish and EPA-DHA intake using analysis of variance models adjusted for age, sex, dietary and lifestyle factors and key determinants of FGF23. Patients consumed on average 15 g of fish and 139 mg EPA-DHA/day. Median FGF23 was 62 pg/mL (IQR 43-98 pg/mL). Higher dietary EPA-DHA and fish intake were associated with lower serum FGF23 levels. Subgroup analyses revealed that particularly in patients with reduced renal function (eGFR <60 mL/min/1.73 m(2)), adjusted FGF23 levels (114, 79, 75 pg/mL, P = 0.0001) were inversely associated with tertiles of EPA-DHA intake. Similarly, we observed an inverse association between fish consumption and serum FGF23 levels in adjusted analyses. CONCLUSION: A higher intake of fish and dietary n-3 fatty acids (EPA-DHA) is related to lower circulating FGF23 levels in renal transplant recipients. Further research is needed to assess the causality of this association and the clinical implications.

Gold nanoparticles developed in sol-gel derived apatite--bioactive glass composites.

The study is focussed on synthesis and characterisation of a new sol-gel derived composite system consisting of nanocrystalline apatite, bioactive glass and gold nanoparticles, which are of interest both for regenerative medicine and for specific medical applications of the releasable gold nanoparticles. Samples dried at 110°C and then heat treated for 30 min at 300 and 500°C were investigated by thermal analysis (DTA/TG), X-ray diffraction (XRD), UV-VIS-NIR, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Photoelectron(XPS) spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Gold nanoparticles and nanocrystalline apatite are developed already after heat treatment at 300°C. XPS analysis clearly revealed the presence of both metallic and ionic gold species. The development of gold nanoparticles was evidenced by UV-VIS-NIR and TEM analysis, and their size increased from few nanometers to 25 nm by increasing the treatment temperature from 300 to 500°C. The bioactivity of the samples immersed in simulated body fluid was demonstrated by XRD and SEM results.

3-Aminopropyl-Triethoxysilane Functionalized Graphene Oxide for Silane-Based Consolidation Treatments to Increase Mortar Performances.

The influence of chemically converted GO (graphene oxide) functionalized with APTES (3-aminopropyl-triethoxysilane) and unfunctionalized GO, dispersed in ethanolic solution of TEOS (tetraethyl orthosilicate), on the performances of the mortar samples, such as capillary water absorption and compressive strength was evaluated. The effect of the GO based nanomaterials (GO and GO functionalized with APTES) on the mortar microstructure was investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The multifunctionality of the mortar brushed with GO based nanomaterials consolidation suspension was proved by the results (i) of the mechanical tests which show an improvement of the compressive strength and (ii) the capillary water absorption results which indicate the decreasing of the water penetration speed. For the mortar samples brushed with GO consolidation suspension, an increase value for the compressive strength of approximately twice compared to the untreated control samples and a decreased value for the capillary absorption water coefficient with one order of magnitude in comparison with the untreated control samples were obtained.

Mixture of Graphene Oxide/Phosphoric Acid/Melamine as Coating for Improved Fire Protective Performance and Enhancement of Surface Electrical Properties on Wood Chipboard.

Looking for multifunctional materials, an assessment of the performances both as fire retardant and generator of electrically conductive surfaces for a three component mixture of graphene oxide, phosphoric acid and melamine applied on wood chipboard was performed. A simple approach was used to investigate the intumescent char formation and quantify the loss mass during vertical burning tests, in which the prepared samples were exposed for a certain time interval to a flame generated by an ethanol lamp in ambient conditions. Moreover, mass loss evolution and structural changes that occur during the burning process were more comprehensive investigated by differential thermal and thermogravimetric (DTA/TGA) techniques. By comparing the performances between the wood chipboard samples without any coverage and those covered with one or multiple component mixture, an increase of protection against the fire action was noticed when the three component mixture was used. Also, an improvement of the electrical properties was observed, after flame exposure of the samples covered with multiple layers (i.e., two and three), when the three component mixture was used. Morphological and structural investigations by microscopy (optical and electronic-SEMEDX), X-ray diffraction (XRD) and spectral (Raman, FTIR) methods are described. An assessment of market potential is also discussed.

Skin wound regeneration with bioactive glass-gold nanoparticles ointment.

The bioactive glasses can lead to the promotion of growth of granulation tissue, while the gold nanoparticles (AuNPs) can induce the acceleration of wound healing including tissue regeneration, connective tissue formation, and angiogenesis. The aim of this study was to evaluate the impact of using the bioactive glass (BG) and BG-AuNPs composites on skin wound healing in experimental rat models for 14 days. Sol-gel derived BGs and BG-AuNPs composites mixed with Vaseline at 6, 12 and 18 wt% were used to evaluate the repair response of the skin. During the process of healing, granulomatous reaction was observed in the wound treated with 12 and 18 wt% BG-Vaseline ointments. Furthermore, a strong vascular proliferation and complete wound regeneration were found in 18%BG-AuNPs-Vaseline treated groups. The results derived from the performed investigations revealed that the 18% BG-AuNPs-Vaseline ointment is a promising candidate for wound healing applications.

Novel bioactive glass-AuNP composites for biomedical applications.

The bioactive glasses doped with gold nanoparticles (AuNPs) are very attractive materials due to their potential in medical applications. In the present study Pluronic-nanogold hybrid nanoparticles were introduced during the sol-gel route of the SiO2-CaO-P2O5 glasses preparation. The obtained samples were characterized by UV-vis spectroscopy, X-ray diffraction, FT-IR spectroscopy, transmission electron and scanning electron microscopy and afterwards they were investigated in terms of bioactivity, protein adsorption and cells viability. The in vitro bioactivity assessment shows the increase of the number of agglomerated spherical shapes of apatite layers for all Au containing samples, but apatite like structure sizes are influenced by the AuNP content. Beside the spherical shapes, three-dimensional flower-like nanostructures were observed on the surface of the glass with 0.2mol% Au2O. Zeta potential and fluorescence spectroscopy measurements evidenced that the amount of serum albumin adsorbed onto the composites surface increases with the AuNP content. FT-IR measurements point out that the secondary structure of the adsorbed proteins presents few minor changes, indicating biocompatibility of the AuNP doped glasses. The good proliferation rate of Human keratinocytes cells obtained in the presence of samples with 0.15 and 0.2mol% Au2O is comparable with the values achieved from free AuNP, fact that proves the preservation of AuNP properties after their incorporation inside the bioactive glass matrices.

Gold films deposited over regular arrays of polystyrene nanospheres as highly effective SERS substrates from visible to NIR.

Gold nanostructured films of various thicknesses (15, 30, and 60 nm) are deposited over regular arrays of polystyrene nanospheres in an attempt to evaluate their potential as SERS-active substrates. Atomic force microscopy is used to topographically characterize the substrates as well as to ensure the thickness of the deposited gold films. The optical response of the prepared substrates recommends their use in SERS experiments with multiple laser lines from visible and NIR spectral domains. The assessment of the substrates' SERS activity is performed by using the 532, 633, and 830 nm excitation lines and different average enhancement factor (EF) values are obtained depending on the film thickness and employed laser line. The 60 nm gold nanostructured film generates the greatest local electromagnetic field confinement under NIR excitation and consequently gives rise to maximum SERS enhancement. The large tunability of surface plasmon excitation combined with the advantage of relatively high exhibited average EF values obtained under NIR excitation recommends these substrates as outstanding candidates for upcoming investigations of biological relevant molecules.

Attachment and conformational changes of collagen on bioactive glass surface.

The proteins adsorption on biomaterials surface leads to changes in their structural conformation that may further influence the adhesion, migration and growth of cells. The aim of this study was to examine the attachment of collagen (calf skin type I) on bioactive glass powders and the conformational changes of the protein. Scanning electron microscopy analysis and X-ray photoelectron spectroscopy measurements indicate that the collagen cover the glass surface in a nanometric thin layer. The infrared amide I absorption signal shows pronounced changes in the secondary structure of the adsorbed collagen.

Bioactive and biocompatible copper containing glass-ceramics with remarkable antibacterial properties and high cell viability designed for future in vivo trials.

In the present study our interest is focused on finding the efficiency of 60SiO2·(32 - x)CaO·8P2O5·xCuO (mol%) glass-ceramics, with 0 ≤ x ≤ 4 mol%, in terms of bioactivity, biocompatibility, antibacterial properties and cell viability in order to determine the most appropriate composition for their further use in in vivo trials. The sol-gel synthesized samples show a preponderantly amorphous structure with a few crystallization centers associated with the formation of an apatite and calcium carbonate crystalline phases. The Fourier Transform Infrared (FT-IR) spectra revealed slightly modified absorption bands due to the addition of copper oxide, while the information derived from the measurements performed by transmission electron microscopy, UV-vis and electron paramagnetic resonance spectroscopy showed the presence of ions and metallic copper species. X-Ray photoelectron spectroscopic analysis indicated the presence of copper metallic species, in a reduced amount, only on the sample surface with the highest Cu content. Regarding in vitro assessment of bioactivity, the results obtained by X-ray diffraction, FT-IR spectroscopy and scanning electron microscopy, demonstrated the formation of a calcium phosphate layer on all investigated sample surfaces. The inhibitory effect of the investigated samples was more significant on the Pseudomonas aeruginosa than the Staphylococcus aureus strain, the sample with the lowest concentration of copper oxide (0.5 mol%) being also the most efficient in both bacterial cultures. This sample also exhibits a very good bactericidal activity, for the other samples it was necessary to use a higher quantity to inhibit and kill the bacterial species. The secondary structure of adsorbed albumin presents few minor changes, indicating the biocompatibility of the glass-ceramics. The cell viability assay shows a good proliferation rate on samples with 0.5 and 1.5 mol% CuO, although all glass-ceramic samples exhibited a good in vivo tolerance.

Bioactivity and protein attachment onto bioactive glasses containing silver nanoparticles.

There is much interest in silver containing glasses for use in bone replacement owing to the demonstrated antibacterial effect. In this work, 2 and 8 mol % of silver was added during the sol-gel process to the composition of a bioactive glass belonging to CaO-SiO(2 -P(2)O(5) system. The samples were characterized by means of ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques to demonstrate that the silver is embedded into the glass matrix as nanoparticles. Bioactivity test in simulated body fluid proved that the presence of silver in the bioactive glass composition, even in high amount, preserve or even improve the bioactivity of the starting glass, and consequently, leads to the carbonated apatite formation, which is the prerequisite for bioactive materials to bond with living bones. Complementary information proving these findings were delivered by performing X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and XPS measurements. The presence of silver also improves protein binding capability to the bioactive glass surface as demonstrated by cw-electron paramagnetic resonance experiments and XPS measurements.