An Electrochemical Biosensor Platform for Testing of Dehydroepiandrosterone 3‐Sulfate (DHEA−S) as a Model for Doping Materials

Endogenous steroids such as dehydroepiandrosterone (DHEA) and dehydroepiandrosterone 3‐sulfate (DHEA?S) have commonly used as doping materials by athletes and to date novel techniques are needed for detection of these molecules. In this study, antibody‐based electrochemical biosensor has developed for testing level of the DHEA?S. For this aim, gold surfaces were initially modified with cysteamine (Cys) and then, DHEA?S antibody was immobilized on the surface via glutaraldehyde (GA) as a crosslinking agent. The stepwise modification of electrode surface was monitored by using various electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Linear range was determined as 2.5–100 ng/mL DHEA?S using differential pulse voltammetry (DPV) technique, as well. Moreover, repeatability (±S.D.), coefficient of variation (%) and limit of detection (LOD) values were calculated as 0.033, 1.030 and 3.971, respectively. Also, DHEA?S in synthetic serum and urine samples were successfully determined with standard addition method and confirmation analysis were performed with liquid chromatography quadrupole‐time of flight mass spectrometry (LC‐QTOF/MS) system. The selectivity was studied with the addition of some interfering molecules (testosterone, bovine serum albumin (BSA), cholesterol, uric acid, lactic acid, codein (COD), ascorbic acid, DHEA). Consequently, this work is proposed as practical, innovative and cost‐effective technique that can be easily adapted for the miniaturized form for the analysis of other doping substances as well as DHEA?S for the future works.     

in vitro Selection of Aptamer for Imidacloprid Recognition as Model Analyte and Construction of a Water Analysis Platform

Pesticide use in agriculture is one of the threats to water safety. Therefore, detection of pesticide residues is crucial for human health. Compared to conventional chromatographic methods, aptasensors are promising tools for fast, cheap and sensitive detection of environmental contaminants. To the best of our knowledge, such an aptasensor has not been reported for imidacloprid (Imi) which is one of the most widely used pesticides. In order to meet this demand, we initially selected two novel aptamers designated as ‘Apta‐1’ and ‘Apta‐2’ by graphene oxide‐SELEX (GO‐SELEX) method. Then, these aptamers were used to fabricate the gold electrode‐based aptasensor platforms and characterized by using electrochemical methods such as cyclic voltammetry, and electrochemical impedance spectroscopy as well as X‐Ray photoelectron spectroscopy. It was found that the limit of detection value of Apta‐1 based sensor for the Imi was found better than Apta‐2 based system, although linear ranges were similar. Based on that finding, Apta‐1 based system was further tested against possible interference molecules. The proposed platform was successfully used for detection of very low concentrations of Imi in the range of ng/mL. Thus, it eliminates the need for sample pre‐treatment and enables a practical analysis in real wastewater samples.     

阴离子对鼠尾草提取物中Ni盐前体绿色合成的NiO纳米粒子磁性和结构性能的影响

采用绿色合成方法,将鼠尾草提取物用作还原和封端剂合成氧化镍纳米颗粒(NiO NPs)。此外,使用各种前驱体合成了NiO NPs,并使用扫描电子显微镜对其形貌进行了分析。利用傅里叶变换红外光谱和粉末X射线衍射(PXRD)对NiO NPs的结构进行了表征,使用振动样品磁强计测量了它们的磁性。PXRD研究表明,所有合成的NiO NPs都表现出具有高结晶度的面心立方相,并且形成了具有高纯度相的NiO。磁化研究结果表明,3种镍盐(乙酸盐、氯化物和硫酸盐)前驱体合成的NiO NPs分别表现出超顺磁、软铁磁和顺磁行为。     

Nanoemulsion drug delivery by ketene based polyester synthesized using electron rich carbon/silica composite surface

A new carrier matrix for nanoemulsion drug delivery was synthesized from glycine as the raw material, using mesoporous/microporous electron rich carbon-silica composite surface (MAC(800)). MAC(800) was prepared from rice husk in two-stage carbonization. The surface area, pore volume, and pore size distribution of MAC(800) were measured, using nitrogen adsorption isotherms at 77K. The unpaired electron density of MAC(800) was measured in electron spin resonance spectroscopy (ESR), using TEMPOL (4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl) as the reference spin probe. Glycine was converted into ketene at the surface of MAC(800), which further underwent radical polymerization to form a low molecular weight ketene polymer (LMKP) of ester structure. The structure and the properties of LMKP were confirmed through (13)C, (1)H and DEPT nuclear magnetic resonance (NMR) spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and size exclusion chromatography (SEC). The two hydrophilic drugs namely ciprofloxacin hydrochloride (CPH) and gentamicin sulphate (GS) were chosen for the nanoemulsion preparation and characterization. They were characterized for morphology, interaction of drugs with the polymer and their crystallinity, using HR-TEM, DSC and XRD, respectively. The encapsulation efficiency of the LMKP towards the drugs ciprofloxacin hydrochloride and gentamicin sulphate were 26% and 12%, respectively. The dissolution studies of the nanoemulsion were carried out for the pH 6.5, 7.4 and 8.0. The cytocompatibility studies were done for LMKP as well as nanoemulsion using Hep2 epithelial cells.     

Delay‐dependent robust reliable control for uncertain switched neutral systems

This article investigates the robust reliable control problem for a class of uncertain switched neutral systems with mixed interval time‐varying delays. The system under study involves state time‐delay, parameter uncertainties and possible actuator failures. In particular, the parameter uncertainties is assumed to satisfy linear fractional transformation formulation and the involved state delay are assumed to be randomly time varying which is modeled by introducing Bernoulli distributed sequences. The main objective of this article is to obtain robust reliable feedback controller design to achieve the exponential stability of the closed‐loop system in the presence of for all admissible parameter uncertainties. The proposed results not only applicable for the normal operating case of the system, but also in the presence of certain actuator failures. By constructing an appropriate Lyapunov–Krasovskii functional, a new set of criteria is derived for ensuring the robust exponential stability of the closed‐loop switched neutral system. More precisely, zero inequality approach, Wirtinger's based inequality, convex combination technique and average dwell time approach are used to simplify the derivation in the main results. Finally, numerical examples with simulation result are given to illustrate the effectiveness and applicability of the proposed design approach. © 2015 Wiley Periodicals, Inc. Complexity 21: 224–237, 2016     

Activation of p300 histone acetyltransferase by small molecules altering enzyme structure: probed by surface-enhanced Raman spectroscopy

Reversible acetylation of nucleosomal histones and nonhistone proteins play pivotal roles in the regulation of all the DNA templated phenomenon. Dysfunction of the enzymes involved in the acetylation/deacetylation leads to several diseases. Therefore, these enzymes are the targets for new generation therapeutics. Here, we report the synthesis of trifluoromethyl phenyl benzamides and their effect on histone acetyltransferase (HAT) activity of p300. One of these benzamides, CTPB (N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-6-pentadecyl-benzamide), was discovered as a potent activator of the p300 HAT activity. We have found that pentadecyl hydrocarbon chain of CTPB is required to activate the HAT only under certain context. Furthermore, our results show that the relative position of -CF3 and -Cl in CTB (N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-benzamide) is also very critical for the activation. Surface-enhanced Raman spectroscopy (SERS) of p300 and the HAT activator complexes evidently suggest that the activation of HAT activity is achieved by the alteration of p300 structure. Therefore, apart from elucidating the chemical basis for small molecule mediated activation of p300, this report also describes, for the first time, Raman spectroscopic analysis of the complexes of histone-modifying enzymes and their modulators, which may be highly useful for therapeutic applications.     

Simultaneous Determination of Antimony and Lead in Gunshot Residue by Cathodic Adsorptive Stripping Voltammetric Methods

Differential pulse cathodic adsorptive stripping (DPCAdSV) and square wave cathodic adsorptive stripping (SWCAdSV) voltammetric methods were developed for the determination of antimony and lead in gunshot residues. Linear working ranges for DPCAdSV and SWCAdSV methods were (2.0×10^?9–5.0×10^?7) M and (2.0×10^?9–7.0×10^?7) M for antimony and 2.0×10^?9–3.0×10^?7 M (both methods) for lead. The detection of antimony limits were found to be 1.3×10^?9 M for DPCAdSV and 7.3×10^?10 M for SWCAdSV while the corresponding values for lead were 3.0×10^?9 M and 5.8×10^?10 M. Antimony and lead contents obtained by these methods in gunshot residues are in good agreement with those obtained by graphite furnace atomic absorption spectrometric method within a confidence limit of 95%.     

Magnetic and dielectric characterization of alginic acid-Fe3O4 nanocomposite

We have reported the synthesis of water dispersible alginic acid (AA)-Fe₃O₄ nanocomposites. The crystallite size was obtained as 9 ± 2 nm from X-ray line profile fitting. As compared to the particle size of 9.2 nm obtained from TEM analysis, these particles show dominantly single crystalline nature. Dielectric analysis show that the real and imaginary parts of the permittivity of both pure AA and AA-Fe₃O₄ nanocomposite obey the ionic polarization mechanism comprised of ionic conductivity and interfacial or space charge polarization. Magnetization measurements show that the saturation magnetization of AA-capped magnetite is significantly lower than the theoretical bulk value, partly due to the structural distortions on the surface of the particles. Moreover, magnetite does not saturate and exhibits no coercivity above a certain temperature, revealing superparamagnetic behavior of the nanocomposite above a blocking temperature, T_B, of ∼175 K. The magnetic core size, determined by theoretical fitting to the magnetization data at room temperature, is 9.55 nm.     

Manipulation of magnetic nanostructures through low temperature metal–oxygen chemistry: Co/CoO exchange biased nanodonuts and Co nanotips

Dense nanodonut and nanotip type morphologies are shown to self-evolve in ultrathin cobalt films during growth under vacuum, depending on the level of oxygen incorporation and temperature. The nanodonut morphology forms at room temperature and the corresponding magnetic hysteresis shows exchange bias (～35 Oe shift along the field axis), which is attributed to the presence of CoO and its exchange coupling with cobalt. The morphology evolves into nanotip features with increase of growth temperature, with concurrent elimination of the oxide component and exchange bias.