Extraction,optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant,antidiabetic and antihypertensive properties

The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin‐converting enzyme (ACE), α‐glucosidase and α‐amylase. The acetone–water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and α‐glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60 °C, whereas a lower temperature at 40 °C was required to maximise inhibitory activities for ACE, α‐glucosidase and α‐amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and α‐amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and α‐amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and α‐amylase enzymes.     

Synthesis and application of magnetite polyacrylamide amino-amidoxime nano-composites as adsorbents for water pollutants

In this work, we aimed to develop a feasible method for in situ preparation of a magnetite ionic polymer nanocomposite at room temperature. For this purpose, acrylonitrile (AN) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) monomers were copolymerized and crosslinked using different monomer mol ratios in the presence of N,N-methylenebisacrylamide (MBA) as crosslinker to produce ionic crosslinked polymers P(AN-co-AMPS. The nitrile groups were converted to amine amidoxime by reacting with hydroxylamine to increase the adsorption characteristics of the ionic polymers. The produced polymers were swelled in iron cations produced from the reaction of ferric chloride and potassium iodide, followed by reaction with an ammonium hydroxide solution to produce magnetite nano-polymer composites. We performed FT-IR and XRD analysis to determine the chemical and crystalline structures, and assessed the morphologies and magnetite content using SEM, TEM and TGA analyses. We investigated the adsorption capacity and mechanism of the prepared magnetite nano-composites as adsorbents for methylene blue, Co²⁺ and Ni²⁺ cations from water.     

A flow cell for transient voltammetry and in situ grazing incidence X-ray diffraction characterization of electrocrystallized cadmium(II) tetracyanoquinodimethane

An easy to fabricate and versatile cell that can be used with a variety of electrochemical techniques, also meeting the stringent requirement for undertaking cyclic voltammetry under transient conditions in in situ electrocrystallization studies and total external reflection X-ray analysis, has been developed. Application is demonstrated through an in situ synchrotron radiation-grazing incidence X-ray diffraction (SR-GIXRD) characterization of electrocrystallized cadmium (II)-tetracyanoquinodimethane material, Cd(TCNQ)₂, from acetonitrile (0.1 mol dm⁻³ [NBu₄][PF₆]). Importantly, this versatile cell design makes SR-GIXRD suitable for almost any combination of total external reflection X-ray analysis (e.g., GIXRF and GIXRD) and electrochemical perturbation, also allowing its application in acidic, basic, aqueous, non-aqueous, low and high flow pressure conditions. Nevertheless, the cell design separates the functions of transient voltammetry and SR-GIXRD measurements, viz., voltammetry is performed at high flow rates with a substantially distended window to minimize the IR (Ohmic) drop of the electrolyte, while SR-GIXRD is undertaken using stop-flow conditions with a very thin layer of electrolyte to minimize X-ray absorption and scattering by the solution.     

Fabrication of core–shell nanocomposites with enhanced photocatalytic efficacy

The current study establishes the unprecedented involvement in the evolution and production of novel core–shell nanocomposites composed of nanosized titanium dioxide and aniline‐o‐phenylenediamine copolymer. TiO₂@copoly(aniline and o‐phenylenediamine) (TiO₂@PANI‐o‐PDA) core–shell nanocomposites were chemically synthesized in a molar ratio of 5:1 of the particular monomers and several weights of nano‐TiO₂ via oxidative copolymerization. The construction of the TiO₂@PANI‐o‐PDA core–shell nanocomposites was ascertained from Fourier transform IR spectroscopy, UV–visible spectroscopy and XRD. A reasonable thermal behavior for the original copolymer and the TiO₂@PANI‐o‐PDA core–shell nanocomposites was investigated. The bare PANI‐o‐PDA copolymer was thermally less stable than the TiO₂@PANI‐o‐PDA nanocomposites. The core–shell feature of the nanocomposites was found to have core and shell sizes of 17 nm and 19–26 nm, respectively. In addition, it was found that the addition of a high ratio of TiO₂ nanoparticles increases the electrical conductivity and consequently lowers the electrical resistivity of the TiO₂@PANI‐o‐PDA core–shell nanocomposites. The hybrid photocatalysts exhibit a dramatic photocatalytic efficacy of methylene blue degradation under solar light irradiation. A plausible interpretation of the photocatalytic degradation results of methylene blue is also demonstrated. Our setup introduces a facile, inexpensive, unique and efficient technique for developing new core–shell nanomaterials with various required functionalities and colloidal stabilities. © 2018 Society of Chemical Industry     

Preparation of nanocomposite dispersions based on cellulose whiskers and acrylic copolymer by miniemulsion polymerization: Effect of the silane content

A one‐step method was used to prepare stable aqueous nanocomposite dispersions based on cellulose whiskers extracted from the rachis of the date palm tree and a poly(styrene‐co‐2‐ethyl hexylacrylate) copolymer via miniemulsion polymerization. A reactive silane, i.e., methacryloxypropyl triethoxysilane was added to stabilize the dispersion and favor the anchoring of the whiskers on polymer particles. Dynamic light scattering was used to study the effect of the silane and whiskers contents on the average particle size of the polymer. Nanocomposites materials were prepared from these dispersions using a casting/evaporation method. The effect of the silane and whiskers contents on the thermal and mechanical properties were studied using differential scanning calorimetry and dynamic mechanical analysis. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Inactivation of pathogenic Klebsiella pneumoniae by CuO/TiO2 nanofibers: A multifunctional nanomaterial via one-step electrospinning

The fabrication and characterization of one-dimensional CuO/TiO₂ nanofibers with high photocatalytic and antibacterial activities are presented. The CuO/TiO₂ nanofibers were prepared by electrospinning of colloid composed of titanium isopropoxide, poly(vinylpyrroliodine) (PVP) and copper nanoparticles and calcination at 700 °C in air for 1 h. The antibacterial activity was tested using Klebsiella pneumoniae as model organism by calculation of the minimum inhibitory concentration (MIC). The obtained CuO/TiO₂ nanofibers showed prominent photocatalytic activity under visible light to degrade reactive black5 and reactive orange16 dyes in aqueous solutions and effectively catalyze K. pneumoniae inactivation. The decomposition process of the cell wall and cell membrane was directly observed by TEM analysis after the exposure of the K. pneumoniae to the nanofibers. Interestingly, the introduced photocatalyst can be reused with the same photocatalytic activity. Overall, the combination of CuO and TiO₂ can be synergistic and resulted in CuO/TiO₂ composite nanofibers having superior photocatalytic and antimicrobial potential to impede K. pneumoniae growth which causes bacterium to die ultimately.     

Photocatalytic activities of electrospun tin oxide doped titanium dioxide nanofibers

SnO₂ doped TiO₂ electropsun nanofiber photocatalysts were successfully prepared by means of electrospinning process. The surface morphology, structure and optical properties of the resultant products were characterized by field-emission electron microscopy (FE-SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy, photoluminescence (PL) and cathodoluminescence (CL) techniques. The utilized physiochemical analyses indicated that the introduced SnO₂ doped TiO₂ nanofibers have a smooth surface and uniform diameters along their lengths. The photocatalytic performance of the composite nanofibers was tested for degradation of methylene blue (MB) and methyl orange (MO) dye solution under ultraviolet (UV) irradiation. Under the UV irradiation, the photocatalytic reaction rate in case of utilizing SnO₂-doped TiO₂ nanofibers was rapidly increased than that of the pristine TiO₂ nanofibers. Overall, this study demonstrates cheap, stable and effective material for photocatalytic degradation at room temperature.     

Enhanced airborne sound absorption effect in poly(vinylidene fluoride)/(K0.5Na0.5)NbO3-nanofiber composite foams

Introducing electrical conductive function to discharge local piezoelectric effect is found effective for improving airborne sound absorption performance. In this work, instead of conductive fillers, a composite with two piezoelectric materials with opposite piezoelectric responses was explored aiming at enhanced sound absorption effect. Open-cell poly(vinylidene fluoride)/(K_0.5Na_0.5)NbO₃ (PVDF/KNN)-nanofiber composite foams were proposed and investigated for airborne sound absorption purpose. Structural and thermal analyses showed that the KNN nanofibers were well dispersed in the PVDF matrix and enhanced the degree of crystallinity of polar phase of PVDF. Significantly enhanced airborne sound absorption over a broad frequency range was observed in the PVDF/KNN-nanofiber composite foams, with increasing KNN nanofibers. One possible mechanism for the improved sound absorption with the piezoelectric KNN nanofibers with positive piezoelectric coefficient added in the PVDF matrix with negative piezoelectric coefficient is that electrical discharge could be facilitated for energy dissipation with the opposite charges generated through the piezoelectric effects in the two phases with opposite polarity. The experimental results show that the open-cell PVDF/KNN-nanofiber composite foams are promising for broadband airborne sound absorption application, and our analysis shed a light on the strategy in designing piezoelectric composite foam with high sound absorption performance.     

Synthetic Modular Antibody Construction by Using the SpyTag/SpyCatcher Protein-Ligase System

Efforts to engineer recombinant antibodies for specific diagnostic and therapy applications are time consuming and expensive, as each new recombinant antibody needs to be optimized for expression, stability, bio-distribution, and pharmacokinetics. We have developed a new way to construct recombinant antibody-like “devices” by using a bottom-up approach to build them from well-behaved discrete recombinant antibody domains or “parts”. Studies on antibody structure and function have identified antibody constant and variable domains with specific functions that can be expressed in isolation. We used the SpyTag/SpyCatcher protein ligase to join these parts together, thereby creating devices with desired properties based on summed properties of parts and in configurations that cannot be obtained by using genetic engineering. This strategy will create optimized recombinant antibody devices at reduced costs and with shortened development times.