Express detection of nonylphenol in water samples by fluorescence polarization immunoassay

The development of express method for detection of endocrine-disrupting chemicals (EDC) such as alkylphenols is required for ecological monitoring. Several attempts have been made to produce antibodies against 4-nonylphenol (NP) in recent years. This work describes the production of new antibodies against NP and also summarizes the characterization of antibodies obtained earlier. Three approaches used to produce alkylphenol-specific antibodies are compared; these are based on: 1. omega-(4-hydroxyphenyl)nonanoic or omega-(4-hydroxyphenyl)heptanoic acid NP derivatives designed to mimic the linear NP isomer; 2. 4-aminophenol, which potentially mimics various substituted phenolic compounds with different side-chain structures at position 4 of the benzene ring; and 3. a mixture of branched NP isomers, conjugated to the carrier protein via a benzene ring by the Mannich reaction, and expected to be the closest mimic of NP structure by preserving its natural alkyl moiety.Fluorescence polarization immunoassays based on different combinations of antibody and labeled antigen for screening detection of NP were developed and structural aspects of assay sensitivity and specificity were investigated. The assays based on the antisera raised against omega-(4-hydroxyphenyl)nonanoic acid and NP conjugate via Mannich reaction are capable of express detection of NP with detection limit of 7 microg mL(-1 )and assay dynamic range of 18-300 microg mL(-1).     

Modeling supply current transients in a digital integrated circuit

We consider the modeling of supply current transients in a digital integrated circuit (DIC) and its application to DIC fault detection. A numerical example is given, in which the proposed model is applied to calculate the DIC diagnostic parameter.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 56, pp. 114–121, 1985     

Pharmacokinetic study of original and generic levofloxacin tablets

The comparative pharmacokinetic study of the generic levofloxacin tablets (500 mg) produced at the Zakusov Institute of Pharmacology of the Russian Academy of Medical Sciences and the original levofloxacin tablets (500 mg) Tavanic produced by Sanofi Vintron Industry (France) has been performed. The limit of quantitative determination was 25 ng/mL. The pharmacokinetic parameters of the compared preparations have been calculated. The relative bioavailability of the generic drug has been determined (108.6 ± 25.6%).     

Thermodynamic study of sodium decyl sulfate solutions in the region of second critical micelle concentration: 2. Thermodynamic functions of polymorphic micellar transition and components of its Gibbs energy

Temperature dependences of the thermodynamic functions of polymorphic micellar transition in the region of second critical micelle concentration are calculated based on data on heat capacities of sodium decyl sulfate solutions obtained previously by scanning calorimetry. Equilibrium constants and fractions of surfactant molecules aggregated into spheroidal and cylindrical micelles are calculated. Using the models of the ellipsoid of revolution and cylinder, components of the equilibrium Gibbs energy of intermicellar transition are calculated.     

Thermodynamic study of sodium decyl sulfate solutions in the region the second critical micellization concentration: 1. Volumetric and heat capacity properties

Densitometry and precision adiabatic scanning calorimetry are used to reveal a number of volumetric and heat capacity properties of sodium decyl sulfate in the region of the second critical micelle concentration. Heat capacities are established in a wide temperature range. The coefficients of thermal expansion, apparent and partial mole expandabilities, volume, heat capacities, and excess partial mole heat capacities are calculated. The analysis of variations in these thermodynamic properties occurring upon variations in concentration and temperature makes it possible to identify the structural variations in sodium decyl sulfate micelles that are relevant to the transition of micelles from globular to cylindrical forms.     

Silanized quantum dots as labels in lateral flow test strips for C-reactive protein

The paper describes the first use of silanized semiconductor core-shell quantum dots as fluorescent labels for macromolecule, C-reactive protein determination in blood plasma. The controlled synthesis of CdSe cores, with successive shells of CdS, CdZnS, ZnS and coating with transparent, stable, and inert silica shell, provides quantum dots with a narrow emission band, high quantum yield, and prolonged signal stability. Finally, the quantum dots were conjugated with specific antibodies via carboxylic groups on the silica surface. The method was further used for the immunochromatographic assay of C-reactive protein, a diagnostically important inflammatory biomarker. Assays with both the fluorescent QDs and a widely used colloidal gold label were developed in parallel and compared. The silanized quantum dots provide a more sensitive assay with a detection limit of 1?ng/mL for C-reactive protein in standard solutions, whereas the common assay has a detection limit of 10?ng/mL. The possibility of quantitative evaluation of analyte content by a portable device was demonstrated; the accuracy of the measurements was in the range of 5%–10%. The tests were used to determine C-reactive proteins in human plasma samples. The selected optimized protocol for these samples is based on a 4-fold dilution. The final working range of the assay, 4–1,200?ng/mL, covers practically all important interval of C-reactive protein values for the characterization of acute, chronic, and local inflammatory processes. Due to their high physical stability and inertness as well as intense, stable, and reproducible fluorescence, silanized quantum dots may be applied for high-sensitive assays for different analytes.     

Preparation of antibodies and development of enzyme-linked immunosorbent assay for nonylphenol

Polyclonal rabbit antibodies against nonylphenol (NP), the main product of nonionic surfactants destruction, were obtained and applied for immunoenzyme assay (ELISA). Two approaches to immunogen synthesis were compared. The first was direct coupling of a mixture of NP isomers to the carrier protein by Mannich reaction. The second was formation of amide bonds between 7-(p-hydroxyphenyl)heptanoic acid (HHA), a linear carboxylated analog of NP, and the carrier protein. Anti-HHA antibodies showed a low affinity to technical NP, whereas with Mannich synthesis it was possible to generate antibodies specific to branched NP molecules. An indirect competitive ELISA was developed based on the anti-NP antibodies. The detection limit of the analysis is 10 ng/mL, with a total duration of around 3 h. The developed ELISA can be applied for group-specific determination of nonionic surfactants and their toxic metabolites. The possibility of NP detection in environmental water matrices using the proposed ELISA without loss of sensitivity is explored.     

Quantitave determination of losartan and its metabolite E-3174 in rat urine

A technique for the quantitative determination of losartan and its metabolite E-3174 in biological liquids (rat urine) has been developed. The analysis was carried out using high-performance liquid chromatography coupled with fluorescence detection. The technique??s detection limit for losartan and E-3174 was equal to 2.5 ng/mL and 5 ng/mL, respectively.     

Pretreatment-free immunochromatographic assay for the detection of streptomycin and its application to the control of milk and dairy products

A rapid pretreatment-free immunochromatographic assay was developed for the control of the streptomycin (STR) content in milk and dairy products. The assay is based on the competition between an immobilized STR–protein conjugate and STR in a sample to be tested for the binding to monoclonal anti-STR antibodies conjugated to colloidal gold during the flow of the sample along a membrane strip with immobilized reactants. It is possible to improve the cut-off level of positive and negative samples distinguished by a change in the molar STR to protein ratio in the immobilized conjugate. The cut-off level (500 ng mL⁻¹) thus achieved corresponds to the stated MRL of STR in milk and dairy products. For STR concentrations in the range of 16–250 ng mL⁻¹ its content can be quantitatively measured based on the degree of binding of a colloidal gold label in the test strip zone with the immobilized STR–protein conjugate. The duration of the assay is 10 min. The selected sizes of membrane pores and colloidal gold particles allow the assay to be carried out at room temperature without additional reactants and pretreatment. The applicability of the assay for milk, whole milk, sour clotted milk, and kefir with different fat content (from 0.5% to 6%) was confirmed. The results of quantitative immunochromatographic assay show good correlation with traditional ELISA (r was equal to 0.935 and 0.940 for the series tested).     

Thermodynamics of the surfaces of nonionic spherical micelles with relatively large extensions of the interfacial layer

The structural properties of nonionic spherical micelles with relatively large extensions of the interfacial layer are investigated, and the size dependences of their adsorption, interfacial tension, and chemical potential are obtained. Such familiar thermodynamic relationships as the Gibbs and Laplace equations, the differential equation for the chemical potential, and the concept of hydrophilic–lipophilic balance are used. The method is applied to micelles formed in surfactant solutions of a homologous series of tetraethylene glycol alkyl ethers. The region of the existence of micellar solutions and the structural characteristics of the interfacial layer of micelles are determined. The interfacial tension minimum corresponding to ideal hydrophilic–lipophilic balance in the micelle interfacial layer is detected. The chemical potential is negative over the range of the homologous series, and its derivative with respect to the tension radius is also negative.