Antibacterial composite membranes of polycaprolactone/gelatin loaded with zinc oxide nanoparticles for guided tissue regeneration

The bacterial colonization of absorbable membranes used for guided tissue regeneration (GTR), as well as their rapid degradation that can cause their rupture, are considered the major reasons for clinical failure. To address this, composite membranes of polycaprolactone (PCL) and gelatin (Gel) loaded with zinc oxide nanoparticles (ZnO-NPs; 1, 3 and 6 wt% relative to PCL content) were fabricated by electrospinning. To fabricate homogeneous fibrillar membranes, acetic acid was used as a sole common solvent to enhance the miscibility of PCL and Gel in the electrospinning solutions. The effects of ZnO-NPs in the physico-chemical, mechanical and in vitro biological properties of composite membranes were studied. The composite membranes showed adequate mechanical properties to offer a satisfactory clinical manipulation and an excellent conformability to the defect site while their degradation rate seemed to be appropriate to allow successful regeneration of periodontal defects. The presence of ZnO-NPs in the composite membranes significantly decreased the planktonic and the biofilm growth of the Staphylococcus aureus over time. Finally, the viability of human osteoblasts and human gingival fibroblasts exposed to the composite membranes with 1 and 3 wt% of ZnO-NPs indicated that those membranes are not expected to negatively influence the ability of periodontal cells to repopulate the defect site during GTR treatments. The results here obtained suggest that composite membranes of PCL and Gel loaded with ZnO-NPs have the potential to be used as structurally stable GTR membranes with local antibacterial properties intended for enhancing clinical treatments

Tribological Response of δ-Bi2O3 Coatings Deposited by RF Magnetron Sputtering

Bismuth oxide (Bi2O3) coatings and composite coatings containing this oxide have been studied due to their potential applications in gas sensing, optoelectronics, photocatalysis, and even tribology. Two parametric models based on chemical features have been proposed with the aim of predicting the lubricity response of oxides. However, such models predict contradictory values of the coefficient of friction (COF) for Bi2O3. In this study, we deposited Bi2O3 coatings, via magnetron sputtering, on AISI D2 steel substrates to evaluate the tribological responses of the coatings and determine which parametric model describes them better. Experimentally, only coatings presenting the cubic defective fluorite-like δ-Bi2O3 phase could be evaluated. We performed pin-on-disk tests at room temperature and progressively increasing temperatures up to 300 °C using alumina and steel counter-bodies. Low wear and COFs (0.05 to 0.15) indicated that the δ-phase behaves as a lubricious solid, favoring the validity of one of the models. An alternative explanation is proposed for the low COF of the defective fluorite-like structure since it is well known that it contains 25% of anionic vacancies that can be ordered to form low shear-strength planes, similar to the Magnéli phases. Two challenges for future potential applications were observed: one was the low adhesion strength to the substrate, and the other was the thermal stability of this phase.This research was funded by PAPIIT-UNAM Project IV200222.Peer reviewe

Effects of atomic ordering of Zirconium oxide nanomodification on stem cell differentiation

The present study shows that the atomic ordering of ZrO2 thin films influences the osteoblastic differentiation of human mesenchymal stem cells (hMSCs). The amorphous ZrO2 film produced a better hMSCs response than the bare Ti surfaces, characterized by a higher production of osteoblastic markers, suggesting that amorphous ZrO2 coatings may enhance bone formation around implants. Slight differences were observed for the surface properties of amorphous and nanocrystalline ZrO2 thin films, being significant the larger barrier properties of the amorphous film

Hydrazine modified g-C3N4 with enhanced photocatalytic activity for degradation of indigo carmine

Polymeric graphitic carbon nitride (g-C3N4) was obtained from urea and modified by heat polymerization at 550 °C in the presence of hydrazine as a modifier agent. The influence of in-situ generated NH3 by hydrazine decomposition at different contents (0.5, 1, 1.5, and 2 mL) on the physicochemical properties and surface properties (water contact angle and point of zero charge) of the g-C3N4 were investigated. The modified g-C3N4 were analyzed by X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, Fourier Transform Infrared, water contact angle, surface area, and the point of zero charge. The in-situ generated NH3 induced an evolution from nano-flakes to lamellar plate morphology depending on stacked interplanar. The influence of surface properties on the photocatalytic response of the unmodified and modified g-C3N4 was tested in the photodegradation of indigo carmine dye at pH = 3.5 and 6.5 solutions under blue LEDs light. The photostability of the samples was tested after 4 cycles of reaction. The properties (surface area (SA); water contact angle (WCA), and optical gap) influence the photocatalytic response, which was summarized in a single parameter defined as SA/(WCA*gap). The maximum value of this product match with results obtained for the most active photocatalyst (U-Hz1).Fil: Valencia, Karen. Universidad Nacional Autónoma de México; MéxicoFil: Hernández Gordillo, Agileo. Universidad Nacional Autónoma de México; MéxicoFil: Mendez Galvan, Melissa. Universidad Nacional Autónoma de México; México. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Morett, Diego. Universidad Nacional Autónoma de México; MéxicoFil: Rodil, Sandra E.. Universidad Nacional Autónoma de México; Méxic

Effect of the addition of Si into V₂O₅ coatings: Structure and tribo-mechanical properties

Vanadium oxide (V2O5) is one of the lubricious oxides with the potential to be used as a solid lubricant at elevated temperatures. However, the material itself is not hard wear-resistant, so most of the research has focused on adding V into hard nitride coatings that could lead to the formation of a self-lubricating V2O5 layer when heated. The other possible solution, which has been less studied, is to look for mechanisms to enhance the hardness of the oxide coating. In this research, we investigate the effect of the addition of Si into the V2O5 coatings, aiming to find conditions that lead to enhance hardness and/or reduced wear while keeping the high temperature lubricity of the V2O5 structure. For this, Si modified V2O5 coatings were deposited using a dual magnetron sputtering system. The results showed that small additions of Si (&lt;2.0 at%) improved the hardness of the V2O5 coatings up to 5 times while keeping the same temperature dependence of the coefficient of friction than V2O5. Dry sliding experiments using the pin-on-disc configuration against silicon nitride balls were performed at 25, 300 and 600 °C. Wear factors in the 10−7 mm3/Nm range were obtained, indicating a good wear resistance. Further addition of Si into the V2O5 structure led to a loss of the crystalline ordering and a significant reduction in the hardness.</p

Synthesis and properties of Bi5Nb3O15 thin films prepared by dual co-sputtering

International audienceBismuth-based oxides have gained attention because of their particular electronic configuration that enhances the mobility of photogenerated carriers. In this work, we focused on the synthesis, and the evaluation of the physical and photocatalytic properties of Bi5Nb3O15 films. Bismuth niobate films were deposited by dual magnetron co-sputtering, starting from Bi2O3 and Nb independently driven targets. Although the substrates were heated at 150 degrees C during the deposition, the films were amorphous; therefore, they were annealed at 600 degrees C in air for 2 h to obtain the nanocrystalline Bi5Nb3O15 orthorhombic phase. The Bi5Nb3O15 compound is an interesting material for applications in microelectronics due to its high-k dielectric value at the radiofrequency range; another possible and reported application is as photocatalyst for degradation of organic pollutants and water splitting processes. The films structure was confirmed by X-ray diffraction (theta-2 theta and in-plane modes). The Raman and infrared spectra were measured and compared with calculated vibrational modes since they have not been reported in the past. The optical properties (refractive index, extinction and absorption coefficients) of the Bi5Nb3O15 films were estimated using UV-VIS reflectance and transmittance spectroscopy. The optical band gap was estimated assuming an indirect fundamental inter-band transition at 3.25 eV. The prospective to use the Bi5Nb3O15 films as a photocatalyst was evaluated through the measurement of the photo-discoloration of indigo carmine (IC) dye solutions (5 ppm) under UV light irradiation at three pHs: 3.5, 7 and 11. The results showed a decrease in the absorbance spectrum of the IC solution as a function of irradiation time only at acidic pH where almost 100% of degradation was achieved at 270 min; this behavior is probably due to the increment of the adsorption of IC molecules on the positively charged surface. A similar response was observed after 5 cycles without any structural change of the films. (C) 2016 Elsevier B.V. All rights reserved

Efficient α/β-Bi2O3 composite for the sequential photodegradation of two-dyes mixture

A mixture of α/β-Bi2O3 and α-Bi2O3 powders were obtained by a simple solid state reaction–annealing route at 550 °C. The structure, optical properties and surface area of the commercial α and β-Bi2O3 and the synthesized α-phase and α/β-composite were well characterized by X-ray diffraction, diffuse reflectance spectra and N2 physisorption. The annealed sample at 550 °C showed 20% of β-phase, forming a heterojunction of α/β-Bi2O3 whereas annealing at elevated temperature (650 °C) lead to the α-phase. Optical properties showed that the presence of the β-phase is mainly responsible for narrowing the energy band gap. The photocatalytic activity of the commercial α and β-Bi2O3 and the synthesized α-phase and α/β-composite were investigated in degradation of single dyes, Indigo Carmine (IC) and Rhodamine-B (RhB) under both UV and visible light-induced photocatalysis. For the best photocatalyst, the photodegradation in a two-dye mixture solution was systematically studied considering the type of dye, the adsorption capacity of the samples and the behavior of dye photodegradation. The photocatalytic performance of α/β-Bi2O3 was comparatively much higher than the commercial α and β-Bi2O3, indicating that better performance of efficient charge separation and transfer across α/β-Bi2O3 composite was obtained. Possible mechanism of the single dye and two-dye mixture degradation was given by using α/β-Bi2O3 composite