Propofol inhibits the myeloperoxidase activity by acting as substrate through a redox process.

BACKGROUND: Propofol (2,6-diisopropylphenol) is frequently used as intravenous anesthetic agent, especially in its injectable form (Diprivan), to initiate and maintain sedative state during surgery or in intensive care units. Numerous studies have reported the antioxidant and anti-inflammatory effect of propofol. The oxidant enzyme myeloperoxidase (MPO), released from activated neutrophils, plays a key role in host defense. An increase of the circulating MPO concentration has been observed in patients admitted in intensive care unit and presenting a systemic inflammatory response related to septic shock or trauma. METHODS: This study investigates the immunomodulatory action of propofol and Diprivan as inhibitor of the oxidant activity of MPO. The understanding of the redox action mechanism of propofol and Diprivan on the myeloperoxidase chlorination and peroxidase activities has been refined using the combination of fluorescence and absorption spectroscopies with docking and cyclic voltammetry. RESULTS: Propofol acts as a reversible MPO inhibitor. The molecule interacts as a reducing substrate in the peroxidase cycle and promotes the accumulation of compound II. At acidic pH (5.5), propofol and Diprivan do not inhibit the chlorination activity, but their action increases at physiological pH (7.4). The main inhibitory action of Diprivan could be attributed to its HOCl scavenging property. GENERAL SIGNIFICANCE: Propofol can act as a reversible MPO inhibitor at clinical concentrations. This property could, in addition to other previously proven anti-inflammatory actions, induce an immunomodulatory action, beneficial during clinical use, particularly in the treatment of systemic inflammation response syndrome.

Influence of Quenching on the Opto-Electronic Properties of F:SnO2 Layers.

For many opto-electronic applications, F:SnO2 materials must benefit from high transparency, high conductivity, and high mechanical strength even after quenching. The purpose of this study was to investigate the influence of quenching on the opto-electronic properties of the F:SnO2 layers synthesized at high temperature on Si x C y O-coated soda-lime glass by atmospheric chemical vapor deposition. The morphology, structure, and composition of the layers were studied before and after quenching in air- and oxygen-rich atmospheres at 670 °C. The free carrier concentration was reduced by oxygen vacancy (VO) passivation, as well as by F and Na diffusion, with all effects scaling up with quenching time in air. The transmittance also decreased with quenching time as Na impurities acted as absorption and electron recombination centers. In an oxygen-rich atmosphere, the VO passivation was even more emphasized, with however a moderate contribution to conductivity loss. The F:SnO2 layer microstructure and composition were rather fringed through high-temperature deposition. The almost invariable free carrier concentration and transmittance of the F:SnO2 samples quenched in O2 versus air were related to a moderation in Na diffusion. For long quenching times (>20 min) in air, Na and F diffusion prevailed explaining the conductivity drop.

Efficiency enhancement of perovskite solar cells based on opal-like photonic crystals.

Perovskite solar cells have shown a tremendous interest for photovoltaics since the past decade. However, little is known on the influence of light management using photonic crystals inside such structures. We present here numerical simulations showing the effect of photonic crystal structuring on the integrated quantum efficiency of perovskite solar cells. The photo-active layer is made of an opal-like perovskite structure (monolayer, bilayer or trilayer of perovskite spheres) built in a T i O 2 matrix. Fano resonances are exploited in order to enhance the absorption, especially near the bandgap of perovskite material. The excitation of quasi-guided modes inside the absorbing spheres enhances the integrated quantum efficiency and the photonic enhancement factor. More specifically, a photonic enhancement factor as high as 6.4% is predicted in the case of spheres monolayer compared to an unstructured perovskite layer. The influences of sphere's radius and incident angle on the absorbing properties are also estimated. Those numerical results can be applied to the nascent field of photonic structuring inside perovskite solar cells.

Synthesis, characterization, and catalytic evaluation of ruthenium-diphosphine complexes bearing xanthate ligands.

The reaction of [RuCl2(p-cymene)]2 with potassium O-ethylxanthate and a set of nine representative Ph2P-X-PPh2 bidentate phosphines (dppm, dppe, dppp, dppb, dpppe, dppen, dppbz, dppf, and DPEphos) afforded monometallic [Ru(S2COEt)2(diphos)] chelates 1-9 in 62-96% yield. All the products were fully characterized by using various analytical techniques and their molecular structures were determined by X-ray crystallography. They featured a highly distorted octahedral geometry with a S-Ru-S bite angle close to 72° and P-Ru-P angles ranging between 73° and 103°. Bond lengths and IR stretching frequencies recorded for the anionic xanthate ligands strongly suggested a significant contribution of the EtO+[double bond, length as m-dash]CS22- resonance form. 1H NMR and XRD analyses showed that the methylene protons of the ethyl groups were diastereotopic due to a strong locking of their conformation by a neighboring phenyl ring. On cyclic voltammetry, quasi-reversible waves were observed for the Ru2+/Ru3+ redox couples with E1/2 values ranging between 0.65 and 0.80 V vs. Ag/AgCl. The activity of chelates 1-9 was probed in three catalytic processes, viz., the synthesis of vinyl esters from benzoic acid and 1-hexyne, the cyclopropanation of styrene with ethyl diazoacetate, and the atom transfer radical addition of carbon tetrachloride and methyl methacrylate. In the first case, 31P NMR analysis of the reaction mixtures showed that the starting complexes remained mostly unaltered despite the harsh thermal treatment that was applied to them. In the second case, monitoring the rate of nitrogen evolution revealed that all the catalysts under investigation behaved similarly and were rather slow initiators. In the third case, [Ru(S2COEt)2(dppm)] was singled out as a very active and selective catalyst already at 140 °C, whereas most of the other complexes resisted degradation up to 160 °C and were only moderately active. Altogether, these results were in line with the high stability displayed by [Ru(S2COEt)2(diphos)] chelates 1-9.

Sol-gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces.

Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (-P(=O)(OH)2). Strong covalent C-P bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger "tantalum capture agent" effect of phosphonic-modified nanotubes during the sol-gel formation process of the deposits compared to nanotubes bearing oxidized functions (-OH, -C=O, -C(=O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests.