Synthesis, thermal stability, electronic features, and antimicrobial activity of phenolic azo dyes and their Ni(II) and Cu(II) complexes

Four water soluble azo dyes, 4-(isopropyl)-2-[(E)-(4-chlorophenyl)diazenyl]phenol (L ¹), 4-(isopropyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L²), 4-(sec-butyl)-2-[(E)-(4-chlorophenyl) diazenyl]phenol (L ³), 4-(sec-butyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L ⁴), and their Cu(II) and Ni(II) complexes were synthesized and characterized using spectroscopic methods. Examination of their thermal stability revealed similar decomposition temperature of approximately 260–300°C and that they were more thermally stable than their metal complexes. Ni(II) complexes of ligands L² and L⁴ were more stable than the other coordination compounds. Among the synthesized ligands, L² and the complexes Cu(L³)₂ and Ni(L⁴)₂ showed both antimicrobial and antifungal activity. However, the other ligands and the complexes were poorly active against selected microorganisms.     

Fabrication of Sensitive Potentiometric Cholesterol Biosensor Based on Co3O4 Interconnected Nanowires

Highly sensitive, selective, reliable and inexpensive cholesterol biosensors are highly demanded for the routine monitoring of cholesterol molecules in order to prevent heart failure incidents. In this study, Co₃O₄ nanostructures are synthesized using polyvinyl pyrrolidone surfactant as growth template by a low temperature aqueous chemical growth method. The morphology of nanostructures was investigated by scanning electron microscopy and X‐ray diffraction techniques. The nanostructures exhibit interconnected nanowires like morphology with interconnected network of nanowires. The nanostructures of Co₃O₄ are polycrystalline. The cholesterol oxidase was physically adsorbed on the interconnected nanowires of Co₃O₄ for the chemical sensing of cholesterol molecules. The sensor device detected a wide range of cholesterol from 1×10^?7 M to 1×10^?3 M concentrations with sensitivity of ?94.031 mV/decade. A detection limit of 0.035×10^?7 M cholesterol concentration was observed and a fast response time of 10 s was also noticed. The fabricated device is highly stable, selective, sensitive, reproducible and repeatable. All the collected information about presented cholesterol biosensor indicates its potential application for the monitoring of cholesterol concentrations from human blood serum and real‐life samples.     

Molecularly Imprinted Polypyrrole for DNA Determination

In this study graphite electrodes modified by a thin DNA‐imprinted polypyrrole layer, which was able to bind specific target‐DNA, are reported. For this aim, electrochemical synthesis of polypyrrole was performed on a pencil graphite electrode by cyclic voltammetry (CV) or by potential pulse sequences (PPS). The modified electrode surface was used for electrochemical determination of target‐DNA by differential pulse voltammetry. According to our best knowledge this is a first report on the application of DNA‐imprinted polymer for the determination of target‐DNA. The results showed that the molecularly imprinted polypyrrole (MIPPy) layer that formed on the carbon electrode surface was sensitive for target‐DNA, while the nonimprinted polypyrrole layer was not sensitive to the same target‐DNA. Comparison of electrodes modified using PPS and CV techniques is presented.     

Fabrication and characterization of a novel wound scaffold based on polyurethane added with Channa striatus for wound dressing applications

Abstract

Wound healing is a complex process and it involves restoration of damaged skin tissues. Several wound dressings comprising naturally made substances are constantly investigated to assist wound healing. In this research, a new wound dressing based on polyurethane (PU) supplemented with essence of Channa striatus (CS) fish oil was made by electrospinning. Morphological study depicted the reduction in fiber diameter than PU with the addition of fish oil (0.552?±?0.109?μm for 8:1 v/v% and 0.519?±?0.196?μm 7:2 v/v%) than the pristine PU (0.971?±?0.205?µm). Fourier transform infrared spectroscopy (FTIR) analysis revealed the presence of fish oil in the composite as identified through increasing peak intensity. Fish oil resulted in the hydrophilic behavior (88?±?3 (8:1 v/v) and 70?±?6 (7:2 v/v)) as revealed in the contact angle analysis. Thermal gravimetric analysis (TGA) showed the superior thermal behavior of the wound dressing patch compared to the PU. Atomic force microscopy (AFM) analysis insinuated a decrease in the surface roughness of the pristine polyurethane with the added fish oil. Coagulation assays signified the delay in the blood clotting time portraying its anti-thrombogenic behavior. Hemolytic assay revealed the less toxic nature of the developed nanocomposites with the red blood cells (RBC’s) depicting its safety with blood. Hence, polyurethane nanofibers supplemented with fish oil made them as deserving candidates for wound dressing application.     

Analytical method development and validation of anticancer agent, 5-fluorouracil,and its metabolites in biological matrices: An updated review

Abstract

5-fluorouracil (5-FU) refers to a fluorinated pyrimidine analogue that has been widely used as an anticancer agent for colon, head, and neck cancers. Detection of 5-FU and its metabolites; 5-fluorouridine and 5-fluoro-2-deoxyuridine in biological samples allows optimization of pharmacotherapy and encourages fundamental investigations of this medication. The development of accurate and reliable sample preparation, as well as analytical methods, is critical to isolate targeted analytes from complex matrices, apart from increasing detection sensitivity of analytes. With that, this paper presents a review of prior studies pertaining to chromatographic and electrophoretic methods that focused on the analysis of 5-FU and its metabolites in biological matrices such as plasma and urine. This paper concentrates on HPLC, GC and CE systems, which are the most commonly used strategies for analytical separation of 5-FU and its metabolites from samples. Detection of these antineoplastic agents at trace level demands highly sensitive and selective analytical methodologies. Application of these analytical techniques to biological matrices is reviewed with a focus on method development strategies, including types of mobile phases and background electrolytes employed in LC and CE systems.     

Solid‐phase extraction using chloropropyl functionalized sol–gel hybrid sorbent for simultaneous determination of organophosphorus pesticides in selected fruit samples

A new sol–gel hybrid methyltrimethoxysilane‐chloropropyltriethoxysilane was prepared as sorbent for solid‐phase extraction. The extraction efficiency of the prepared sol–gel hybrid methyltrimethoxysilane‐chloropropyltriethoxysilane was assessed by using three selected organophosphorus pesticides, namely, chlorpyrifos, profenofos, and malathion. Gas chromatography–mass spectrometry was used for detection of organophosphorus pesticides. Several vital parameters were optimized to identify the best extraction conditions. Under the optimum extraction conditions, solid‐phase extraction‐methyltrimethoxysilane‐chloropropyltriethoxysilane method showed good linearity range (0.05‐1 μg/mL) with coefficient of determination more than 0.995. The limits of detection obtained were in the range of 0.01–0.07 μg/mL and limits of quantification ranging from 0.03 to 0.21 μg/mL. The limits of detection obtained for the developed method were 2.3–6.5× lower than the limits of detection of commercial octadecyl silica sorbent. Real samples analysis was carried out by applying the developed method on red apple and purple grape samples. The developed method exhibited good recoveries (88.33–120.7%) with low relative standard deviations ranging from 1.6 to 3.3% compared to commercial octadecyl silica sorbent, which showed acceptable recoveries (70.3–100.2%) and relative standard deviations (6.3–8.8%). The solid‐phase extraction‐methyltrimethoxysilane‐chloropropyltriethoxysilane method is presented as an alternative extraction method for determination of organophosphorus pesticides.     

Pyrolysis of poly(phenylene vinylene)s with polycaprolactone side chains

The thermal degradation characteristics of a new macromonomer poly(-caprolactone) with central 4,4′-dicarbaldehyde terphenyl moieties and poly(phenylene vinylene)s with well defined (-caprolactone), (PPV/PCL) as lateral substituents were investigated via direct pyrolysis mass spectrometry. The unexpectedly high thermal stability of the macromonomer was attributed to intermolecular acetylation of benzaldehyde yielding a hemiacetal and causing a crosslinked structure during the pyrolysis. Increased thermal stability of the PCL chains was detected for all samples. The increase in stability of PCL chains was much more pronounced than was detected for poly(p-phenylene)-graft-poly(-caprolactone) copolymer (PPP/PCL); the upward temperature shift was about 100 °C for PPV/PCL and only 20 °C for PPP/CL. This pronounced effect may be due to higher thermal stability of PPV compared to PPP and the decrease in steric hindrance for PPV with PCL side chains.     

Fundamentals and properties of zinc oxide nanostructures: Optical and sensing applications

In this paper we will give an overview of the status of catalytic growth and of low-temperature chemical growth of ZnO nanostructures performed in our laboratory. Particularly results employing different substrates will be discussed. The second part deals with structural and optical properties of ZnO nanorods. The results from high resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM), photoluminescence (PL), Cathodoluminescence (CL), and Electroluminescence (EL), on single nanowires will be shown. Our results on surface morphology, bulk and the position of the catalyst as well as the optical properties including UV emission, lasing and white emission will all be presented and discussed. In the third part experimental results from electroluminescence of ZnO nanorods on different substrates in the UV in addition to excellent white light emission obtained from samples grown at low temperature are to be given and discussed. Finally the sensing of molecules in water by ZnO nanorods will be discussed from a theoretical point of view. Also fundamental properties of polaritons and excitons in ZnO nanostructures are to be highlighted.     

Enhancement of catalytic activity of titanosilicalite-1 - sulfated zirconia combination towards epoxidation of 1-octene with aqueous hydrogen peroxide

Summary Titanosilicalite-1 (TS-1) in combination with sulfated zirconia efficiently catalyzes the epoxidation of 1-octene with aqueous hydrogen peroxide. The presence of both octahedral zirconium and sulfate species in the catalysts enhances the epoxidation rates.