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We developed a fluorescence polarization immunoassay (FPIA) procedure for determining the dibutyl phthalate (DBP) plasticizer, a toxic technogenic environmental pollutant, in water. The procedure is based on the competitive interaction of DBP and fluorophore-labeled DBP with antibodies in the sample, fluorescence excitation by plane-polarized light, and recording the fluorescence polarization of the emitted light. A conjugate of an amino derivative of fluorescein with succinate-dibutyl phthalate was synthesized, and its binding with polyclonal antibodies was confirmed. The FPIA procedure is characterized by a limit of detection for DBP of 0.35 [micro]g/mL and an analytical range from 0.5 to 7.5 [micro]g/mL. The analysis time is 2 min., Author(s): V. S. Baranovskaya [sup.1], A. N. Berlina [sup.2], S. A. Eremin [sup.1] [sup.2] Author Affiliations: (1) grid.14476.30, 0000 0001 2342 9668, Department of Chemistry, Moscow State University, , 119991, [...]

The influence of organic solvents such as methanol and acetonitrile on the results of butachlor immunoassay in samples of rice and rice products was studied. The schemes of enzyme immunoassay using: (a) native antiserum containing specific antibodies to butachlor and antispecies antibodies labeled with horseradish peroxidase, and (b) biotinylated specific antibodies and streptavidin labeled with peroxidase are considered. The close values of IC10 (0.77 and 0.68 ng/mL, respectively) and working range (2.6–165 and 2.4–192 ng/mL, respectively) were established for the two schemes, when analyzing in a mixture of phosphate buffer and methanol in a percentage ratio of 85 : 15, respectively. For the second scheme, the detection of butachlor in butachlor in rice-containing products is shown at 80-132% of the added analyte. A comparison of sample preparation methods allows us to recommend: (a) extraction of butachlor with hexane and re-dissolution of the dry residue in a buffer with 15% methanol or (b) preparation of a methanol extract followed by 6-fold dilution with a buffer solution. [ABSTRACT FROM AUTHOR]

The toxic effects of antimony pose risks to human health. Therefore, simple analytical techniques for its widescale monitoring in water sources are in demand. In this study, a sensitive microplate apta-enzyme assay for Sb3+ detection was developed. The biotinylated aptamer A10 was hybridized with its complementary biotinylated oligonucleotide T10 and then immobilized on the surface of polysterene microplate wells. Streptavidin labeled with horseradish peroxidase (HRP) bound to the biotin of a complementary complex and transformed the 3,3′,5,5′-tetramethylbenzidine substrate, generating an optical signal. Sb3+ presenting in the sample bounded to an A10 aptamer, thus releasing T10, preventing streptavidin-HRP binding and, as a result, reducing the optical signal. This effect allowed for the detection of Sb3+ with a working range from 0.09 to 2.3 µg/mL and detection limit of 42 ng/mL. It was established that the presence of Ag+ at the stage of A10/T10 complex formation promoted dehybridization of the aptamer A10 and the formation of the A10/Sb3+ complex. The working range of the Ag+-enhanced microplate apta-enzyme assay for Sb3+ was determined to be 8–135 ng/mL, with a detection limit of 1.9 ng/mL. The proposed enhanced approach demonstrated excellent selectivity against other cations/anions, and its practical applicability was confirmed through an analysis of drinking and spring water samples with recoveries of Sb3+ in the range of 109.0–126.2% and 99.6–106.1%, respectively. [ABSTRACT FROM AUTHOR]

The present work is performed on Pb2+ detection via electrochemical sensor. The novel aptasensor was developed by modification of glassy carbon electrode (GCE) with reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) modified with ssDNA. The synthesized nanoparticles were characterized by HRTEM (high resolution transmission electron microscopy), SAED (selected area electron diffraction), UV–Vis spectrophotometer, FTIR, and XPS. The rGO was prepared by electrochemical reduction and thickness of rGO sheet was 0.5 to 1 nm. The average AuNPs size was 20–25 nm. The Pb2+ ion binds with specific ssDNA, and it will induce conformational changes of the aptamer and corresponding modulation of electrochemical signals. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for Pb2+ detection and optimization of sensor. The proposed aptasensor exhibits high sensitivity toward detection of Pb2+ ions with a detection limit of 1.52 nM and linear range of 5–50 nM at a signal-to-noise ratio of 3. Moreover, this aptasensor produces satisfactory results in environmental water samples analysis. The results of the newly developed aptasensor show better sensitivity and selectivity than the previously described electrochemical sensor. [ABSTRACT FROM AUTHOR]

Arsenic is toxic, so being able to detect and monitor arsenic in aqueous environments is important. Here, we report a biosensor for As3+ (Arsenic (III)) which uses a glassy carbon electrode modified with Ag-Au alloy NPs (i.e. Silver and gold alloy nanoparticles) and loaded with an aptamer. The electrode contains apta deep trapped Ag-Au alloy NPs, and the detection method employs cyclic voltammetry and differential pulse voltammetry. Captured As3+ ions undergo electrochemical reaction, producing a significant increase in the current which is observed in the voltammetry curves. This current increase is a result of the electrocatalytic properties of the NPs. The electrode is used for the determination of As3+ in real water samples. The activity curve is linear for As3+ concentrations of 0.01µg/L to 10 µg/L, and the detection limit is 0.003 × 10−3µg/L. The operation of the biosensor is reproducible, stable, and selective, and the biosensor performs well in determining As3+ in water from natural water courses, lakes, and wells. [ABSTRACT FROM AUTHOR]

Open-ring derivatives of beta-lactams do not inhibit bacterial growth but retain several biological activities. In this regard, methods of antibiotic control should be characterized by specificity to such derivatives. The objective of this study was to evaluate commercially available immunoreagents for the detection of beta-lactams from the point of view of their selectivity with respect to the open-ring derivatives of lactams. The enzyme-linked immunosorbent assays (ELISA) was used for this purpose. Ampicillin was hydrolyzed by acid and alkaline treatments, and opening of the lactam ring was confirmed spectrophotometrically. It was shown that either selective detection of only native ampicillin or integrated detection of both its states could be realized depending on the immunoreagents. The detection limit for native ampicillin for both assays was 10 ng/mL, where as cross-reactivity to the derivatives with an open ring was <0.01% for the first case and 61.5-64.2% for the second case. The established variability is critical in interpreting the data of immunodetection and should be controlled for grounded evaluation of pharmaceuticals and foods. [ABSTRACT FROM AUTHOR]