Detection of Senecionine in Dietary Sources by Single-Use Electrochemical Sensor

Pyrrolizidine alkaloids (PAs) are produced by plants as secondary compounds that are the most widely distributed natural toxins. There have been many cases of human toxicity caused by consumption of toxic plant species, as herbal teas and grain or grain products contaminated with PA-containing seeds have been reported. Companies that produce dried spices and tea leaves should examine the PA level in their products. For the first time in the literature, a simple and inexpensive electrochemical assay based on a single-use sensor was introduced for quantitative determination of senecionine (SEN) in the most frequently contaminated food sources. SEN was immobilized on a pencil graphite electrode surface by the passive adsorption technique. Differential pulse voltammetry (DPV) was used to evaluate the oxidation signal of SEN, which was observed to be around +0.95 V. The oxidation signal was specific to the SEN in the sample, and the current value was proportional to its concentration. The selectivity of our assay was also tested in the presence of other similar PAs such as intermedine, lycopsamine, and heliotrine. The detection limit is calculated by developed assay and found to be 5.45 µg/mL, which is an acceptable concentration value of SEN occurring at toxic levels for consumers. As an application of the developed sensor in food products, the electrochemical detection of SEN was successfully performed in flour and herbal tea products.

Active and passive adsorption of 47 trace atmospheric volatile organic compounds onto carbon nanotubes

CNTs need to be cleaned at high temperature under vacuum and stored in an inert gas environment to prevent immediate contamination by adsorbed trace atmospheric VOCs.

Application of the expeditionary geochemical laboratory in the conditions of the polar regions (on the example of portative chromatography with passive concentrators)

At present, the method of passive adsorption, using German technology sorbers, is widely used to search for hydrocarbon deposits in the Polar region. Their efficiency is about 55%. The advantages of using domestic technology "ЭХО с ПКК" in the areal conditions of the Arctic are shown. This is the formation of a digital geochemical database directly during field work. To increase efficiency in the Arctic, methods of passive adsorption require significant refinement.

Behavior and Mechanism of Cesium Biosorption from Aqueous Solution by Living Synechococcus PCC7002

Many efforts have focused on the adsorption of metals from contaminated water by microbes. Synechococcus PCC7002, a major marine cyanobacteria, is widely applied to remove metals from the ocean’s photic zone. However, its ability to adsorb cesium (Cs) nuclides has received little attention. In this study, the biosorption behavior of Cs(I) from ultrapure distilled water by living Synechococcus PCC7002 was investigated based on kinetic and isotherm studies, and the biosorption mechanism was characterized by Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, and three-dimensional excitation emission matrix fluorescence spectroscopy. Synechococcus PCC7002 showed extremely high tolerance to Cs ions and its minimal inhibitory concentration was 8.6 g/L. Extracellular polymeric substances (EPS) in Synechococcus PCC7002 played a vital role in this tolerance. The biosorption of Cs by Synechococcus PCC7002 conformed to a Freundlich-type isotherm model and pseudo-second-order kinetics. The binding of Cs(I) was primarily attributed to the extracellular proteins in EPS, with the amino, hydroxyl, and phosphate groups on the cell walls contributing to Cs adsorption. The biosorption of Cs involved two mechanisms: Passive adsorption on the cell surface at low Cs concentrations and active intracellular adsorption at high Cs concentrations. The results demonstrate that the behavior and mechanism of Cs adsorption by Synechococcus PCC7002 differ based on the Cs ions concentration.

An Impedimetric Biosensor Based on Ionic Liquid-Modified Graphite Electrodes Developed for microRNA-34a Detection

In the present work, an impedimetric nucleic acid biosensor has been designed for the purpose of detection of microRNA (miRNA). Ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate (IL))-modified chemically activated pencil graphite electrodes (PGEs) were used for the sensitive and selective detection of miRNA-34a. After covalent activation of the PGE surface using covalent agents (CAs), the ionic liquid (IL) was immobilized onto the surface of the chemically activated PGE by passive adsorption. The electrochemical and microscopic characterization of the IL/CA/PGEs was performed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and scanning electron microscopy (SEM). DNA probe concentration, miRNA target concentration, and also the hybridization time and wet adsorption time were optimized by using the EIS technique. Then, the hybridization occurred between specific DNA probes and miRNA-34a was immobilized onto the surface of the IL/CA/PGEs. The impedimetric detection of miRNA-DNA hybrid was performed by EIS. The detection limit (DL) was calculated in a linear concentration range of 2–10 µg/mL miRNA-34a target, and it was found to be 0.772 µg/mL (109 nM) in phosphate buffer solution (PBS) and 0.826 µg/mL (117 nM) in diluted fetal bovine serum (FBS). The selectivity of impedimetric biosensor for miRNA-34a was also tested against to other non-complementary miRNA sequences both in buffer media, or diluted FBS.