Light-activated oxidize-mimicking nanozyme for inhibition of pathogenic Escherichia coli

Here we demonstrate the nanozyme properties of histidine-containing carbon nanodots as externally tunable antibacterial agents through irradiation with visible (VIS) light. The correlative (light and electron) microscopic analysis of treated Escherichia coli O157:H7 revealed that the positive charged carbon nanoparticles might readily adsorb at slightly acid pH on the negative charged cellular envelope of bacteria, and thus, inhibit their growth with over 80% efficiency under illumination with VIS light. The reason was that under VIS irradiation in the range 400–500 nm the adsorbed nanoparticles behaved as effective oxidase-mimicking enzymes and generated reactive oxygen species on the labeled cells. Thus, the light-activated artificial nanozyme caused serious physical damaging of bacterial envelope, which was leading to irreversible cellular inhibition. The outcomes of this study are likely to broaden the scope of designed photoactive carbon nanozymes as powerful antibacterial agents against the emergence of antibiotic and multidrug-resistant strains, as well as proposing of new strategies for infection control.     

Short-Term Stability of Whole Blood Polyunsaturated Fatty Acid Content on Filter Paper During Storage at −28 °C

Finger or heel‐pricked blood sampling for fatty acid analysis is suitable especially in newborn infants where blood sampling is difficult and phlebotomy for research can be unethical. The aim of this study was to evaluate dried blood long chain polyunsaturated fatty acids (LC‐PUFA) stability during storage at ?28 °C. We collected 12 blood cord samples that were analyzed immediately after blood drawing, with and without drying the blood on filter paper. Dried samples were then analyzed 7 days and 1, 3, and 6 months after collection. Butylated hydroxytoluene was added to all samples. Fatty acid composition and ¹³C enrichment were measured by gas chromatography and by gas chromatography‐isotope ratio mass spectrometry, respectively. The fatty acid composition, expressed in mol%, of the major LC‐PUFA at day 7 was not statistically different from time 0, however lower values were found by the first month of storage. The ¹³C enrichment of 20:4n‐6 and 22:6n‐3 did not differ during the whole study period. LC‐PUFA analysis from dried umbilical cord blood in neonates should be performed within a week, major losses of LC‐PUFA occur afterwards. However, fatty acids obtained from dried blood maintain their ¹³C enrichment value for up to 6 months and thus these samples are suitable for natural abundance isotopic studies.     

Chromenes from Ageratum conyzoides: Steam distillation,supercritical extraction,and mathematical modeling

The chromenes extraction processes from Ageratum conyzoides by steam distillation and supercritical fluid extraction (SFE) were studied. Essential oil was extracted by saturated steam at 1.0 to 2.0 bar and the SFE was performed at 40ºC and 90 to 200 bar to obtain non-volatile extracts. The essential oil presented two major compounds—precocene I (28.24%) and precocene II (28.55%). At 90 bar, the SFE resulted in higher yield and selectivity for precocene I and II (65.06%). The yield of chromenes varied according to pressure of SFE; however, this behavior was not observed in extracts obtained by steam distillation.     

Derivative cathodic stripping voltammetry in the simultaneous determination of three textile dyes in aqueous solutions

Reactive dyes, such as Procion Yellow, Procion Red, and Procion Blue, were simultaneously determined in aqueous ternary solutions using derivative cathodic stripping voltammetry following adsorption on a hanging mercury drop electrode. An electrochemical cell containing Britton–Robinson buffer solution at pH 8 was used as the supporting electrolyte. The following experimental conditions were established: ?0.100 V deposition potential, 80 s deposition time, 50 mV pulse amplitude, 50 mV s^?1 scan rate, and 0.40 mm² maximum mercury drop size. A linear response was observed over the 0.630 × 10^?3 to 1.050, 1.441 × 10^?3 to 1.572, and 0.198 to 1.570 mg l^?1 ranges for Procion Yellow, Procion Red, and Procion Blue respectively. The detection limits were 0.210 × 10^?3, 0.480 × 10^?3, and 0.066 mg l^?1 respectively, with a relative standard deviation (n = 3) of 1.22%. The accuracy of the method was evaluated by derivative spectrophotometry, certifying the results as a function of proximity. All results were similar, indicating that derivative cathodic stripping voltammetry may be efficiently applied for the simultaneous determination of textile dyes in aqueous ternary solutions.     

Synthesis and in vivo Evaluation of Fluorine‐18 and Iodine‐123 Pyrazolo[4,3‐e]‐1,2,4‐triazolo[1,5‐c]pyrimidine Derivatives as PET and SPECT Radiotracers for Mapping A2A Receptors

Imaging agents that target adenosine type 2A (A_2A) receptors play an important role in evaluating new pharmaceuticals targeting these receptors, such as those currently being developed for the treatment of movement disorders like Parkinson′s disease. They are also useful for monitoring progression and treatment efficacy by providing a noninvasive tool to map changes in A_2A receptor density and function in neurodegenerative diseases. We previously described the successful evaluation of two A_2A‐specific radiotracers in both nonhuman primates and in subsequent human clinical trials: [¹²³I]MNI‐420 and [¹⁸F]MNI‐444. Herein we describe the development of both of these radiotracers by selection from a series of A_2A ligands, based on the pyrazolo[4,3‐e]‐1,2,4‐triazolo[1,5‐c]pyrimidine core of preladenant. Each of this series of 16 ligands was found to bind to recombinant human A_2A receptor in the low nanomolar range, and of these 16, six were radiolabeled with either fluorine‐18 or iodine‐123 and evaluated in nonhuman primates. These initial in vivo results resulted in the identification of 7‐(2‐(4‐(4‐(2‐[¹⁸F]fluoroethoxy)phenyl)piperazin‐1‐yl)ethyl)‐2‐(furan‐2‐yl)‐7H‐pyrazolo[4,3‐e][1,2,4]triazolo[1,5‐c]pyrimidin‐5‐amine ([¹⁸F]MNI‐444) and 7‐(2‐(4‐(2‐fluoro‐4‐[¹²³I]iodophenyl)piperazin‐1‐yl)ethyl)‐2‐(furan‐2‐yl)‐7H‐imidazo[1,2‐c]pyrazolo[4,3‐e]pyrimidin‐5‐amine ([¹²³I]MNI‐420) as PET and SPECT radiopharmaceuticals for mapping A_2A receptors in brain.     

Effect of Plasma Enthalpy on the Structure of La2Zr2O7 Coatings Prepared by Suspension Plasma Spraying

La₂Zr₂O₇ coatings, prepared by suspension plasma spraying, have been studied by X‐ray diffraction (XRD) as a function of torch power. Rietveld refinements of high‐resolution XRD data show that with increasing plasma temperature (as a result of the increasing torch power), the La₂Zr₂O₇ coatings remain cation ordered but progressively anion disordered.     

In vitro antioxidant, anticoagulant and antimicrobial activity and in inhibition of cancer cell proliferation by xylan extracted from corn cobs

Xylan is one of most abundant polymer after cellulose. However, its potential has yet to be completely recognized. Corn cobs contain a considerable reservoir of xylan. The aim of this work was to study some of the biological activities of xylan obtained from corn cobs after alkaline extraction enhanced by ultrasonication. Physical chemistry and infrared analyses showed 130 kDa heteroxylan containing mainly xylose:arabinose: galactose:glucose (5.0:1.5:2.0:1.2). Xylan obtained exhibited total antioxidant activity corresponding to 48.5 mg of ascorbic acid equivalent/g of xylan. Furthermore, xylan displayed high ferric chelating activity (70%) at 2 mg/mL. Xylan also showed anticoagulant activity in aPTT test. In antimicrobial assay, the polysaccharide significantly inhibited bacterial growth of Klebsiella pneumoniae. In a test with normal and tumor human cells, after 72 h, only HeLa tumor cell proliferation was inhibited (p < 0.05) in a dose-dependent manner by xylan, reaching saturation at around 2 mg/mL, whereas 3T3 normal cell proliferation was not affected. The results suggest that it has potential clinical applications as antioxidant, anticoagulant, antimicrobial and antiproliferative compounds.     

Evaluation of the Chiral DIANANE Backbone as Ligand for Organolithium Reagents

Novel endo,endo‐2,5‐diaminonorbonane‐derived tertiary C₂‐symmetrical diamines were synthesized via the one‐pot reductive amination of enantiomerically pure norbornane‐2,5‐dione. These ligands were applied to various catalytic reactions such as asymmetric deprotonation, asymmetric bromine‐lithium exchange, and enantioselective addition of aryl‐ and allkylithium reagents to aromatic aldimines.     

Anisotropic photonic properties of III-V nanowires in the zinc-blende and wurtzite phase

Some critical aspects of the anisotropic absorption and emission properties of quasi one-dimensional structures are reviewed in the context of III-V compound semiconductor nanowires. The unique optical and electronic properties of III-V nanowires stem from the combination of dielectric effects due to their large aspect ratio, and their specific crystallographic structure which can differ significantly from the bulk case. The growth conditions leading to single-crystal nanowires with either zinc blende or wurtzite phase are first presented. Dipole selection rules for interband transitions in common III-V compounds are then summarized for the two different phases, and corroborated by ab initio Density Functional Theory calculations of the oscillator strength. The optical anisotropy is discussed considering both the effect of refractive index mismatch between the nanowire and its surroundings and the polarization of the emitting dipoles set by the nanowire crystallographic structure and orientation. Finite Difference Time Domain simulations are finally employed to illustrate the influence of the emitting dipole orientation and the nanowire diameter on the distribution of radiation in the far-field. The importance of the correlation between structural and optoelectronic properties is highlighted in view of potential applications in future nanowire photonics.     

Qualitative identification of permitted and non-permitted colour additives in food products

Colour additives are dyes, pigments or other substances that can impart colour when added or applied to food, drugs, cosmetics, medical devices, or the human body. The substances must be pre-approved by the US Food and Drug Administration (USFDA) and listed in Title 21 of the US Code of Federal Regulations before they may be used in products marketed in the United States. Some also are required to be batch certified by the USFDA prior to their use. Both domestic and imported products sold in interstate commerce fall under USFDA jurisdiction, and the USFDA's district laboratories use a combination of analytical methods for identifying or confirming the presence of potentially violative colour additives. We have developed a qualitative method for identifying 17 certifiable, certification exempt, and non-permitted colour additives in various food products. The method involves extracting the colour additives from a product and isolating them from non-coloured components with a C(18) Sep-Pak cartridge. The colour additives are then separated and identified by liquid chromatography (LC) with photodiode array detection, using an Xterra RP18 column and gradient elution with aqueous ammonium acetate and methanol. Limits of detection (LODs) ranged from 0.02 to 1.49 mg/l. This qualititative LC method supplements the visible spectrophotometric and thin-layer chromatography methods currently used by the USFDA's district laboratories and is less time-consuming and requires less solvent compared to the other methods. The extraction step in the new LC method is a simple and an efficient process that can be used for most food types.