Use of gold nanoparticle-labeled secondary antibodies to improve the sensitivity of an immunochromatographic assay for aflatoxin B1

We describe a sensitive method for the immunochromatographic determination of aflatoxin B1. It is based on the following steps: 1) Competitive interaction between non-labeled specific primary antibodies and target antigens in a sample and in the test zone of a membrane; 2) detection of the immune complexes on the membrane by using a secondary antibodies labeled with gold nanoparticles. The method enables precise adjustment of the required quantities of specific antibodies and the colloidal (gold) marker. It was applied in a lateral flow format to the detection of aflatoxin B1 and exhibits a limit of detection (LOD) of 160 pg?·?mL^?1 if detected visually, and of 30 pg?·?mL^?1 via instrumental detection. This is significantly lower than the LOD of 2 ng?·?mL^?1 achieved by conventional lateral flow analysis using the same reagents. Figure

Immunochromatography with secondary labeled antibodies caused 10-fold decrease of detection limit     

Integration of lateral flow and microarray technologies for multiplex immunoassay: application to the determination of drugs of abuse

We report on a lateral flow microarray that combines multi-spot immunochip technology and immunochromatography. It can serve as a tool for the simultaneous detection of multiple analytes. The test zone of the nitrocellulose support comprises a microarray spotted with up to 32 antigens that can capture labeled gold-antibodies after lateral flow. The detection limits and detectable concentration ranges of the assay were characterized. The method was applied to the determination of drugs of abuse (and their metabolites) in urine, specifically of morphine, amphetamine, methamphetamine, and benzoylecgonine. The assay format is rapid (10 min), and has both a low relative standard deviation (< 9 %) and high recoveries (95–114 %). The detection limits (2–20 ng mL^–1 for drugs of abuse) are comparable to those of conventional single-analyte strip methods.

Comparative Pharmacokinetics and Relative Bioavailability of a New Anxiolytic GML-1 in Tablet Form

Moscow University Chemistry Bulletin - An open, single, crossover, pharmacokinetic study of GML-1 (dose 50 mg/kg) in rabbits after its oral administration in tablets and alone as a substance is...     

Laccase from Coriolus hirsutus as alternate label for enzyme immunoassay

A new label—laccase from the fungus Coriolus hirsutus—was applied for solid-phaseenzyme-linked immunosorbentassays of the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D). Two proposed assays are based on (1) competitive binding of antibody-laccase conjugate with immobilized 2,4-D-protein conjugate and 2,4-D in tested sample, and (2) competition of 2,4-D and 2,4-D-laccase conjugate for binding with immobilized antibodies. Kinetic and concentration dependencies for these reactions were studied, and the ELISAs were optimized in accordance with the data obtained. The elaborated systems perm it the detection of 2,4-D in concentrations down to 10–20ng/mL; time of the assays is 1.5–2 h. The main advantage of the laccase label, in comparison with the widely used peroxidase one, lies in the lack of hydrogen peroxide from substrate mixture, because dissolved oxygen plays the role of oxidizer.     

Enzyme immunoassay for detection of Sudan I dye and its application to the control of foodstuffs

Food safety measures should include the control of the illegal use of banned toxic dyes, including Sudan I as one of the most commonly used coloring agents. A procedure was developed for the enzyme immunoassay of Sudan I carried out in the kinetic mode in order to enhance the performance and rapidity of assays. The achieved limit of detection of Sudan I is 0.13 ng/mL, and the detectable concentration range is from 0.24 to 2.32 ng/mL. The assay time is 50 min. The results obtained by enzyme immunoassay and HPLC for food extracts (tomato paste, chili sauce, spices) showed good correlation. Due to high performance, the new procedure holds promise for the screening control of Sudan I in foodstuffs.     

Immunochromatographic assay for the detection of ochratoxin A

The detection of mycotoxins—toxic contaminants of fungal origin—is an important problem in the food and feed quality control. An immunochromatographic system was developed for the detection of ochratoxin A (OTA), which is one of the priority contaminants in grain. Monoclonal antibodies against OTA and their conjugates with colloidal gold nanoparticles were prepared. The detection is based on the competition of OTA in a sample and an OTA-protein conjugate immobilized on a test strip for the binding to anti-bodies on the colloidal particle surface. The method was tested in the analysis of plant extracts (maize and barley extracts). It was shown that OTA can be detected in a medium with a high content of an organic solvent (up to 35% of methanol). The disappearance of the line in the test zone is visually detected at OTA concentrations starting from 50 ng/mL. In the case of the video-digital detection of changes in the color intensity of the test zone, the limit of detection of OTA is 5 ng/mL. The duration of the assay is 10 min.     

Rapid polyelectrolyte-based immunofiltration technique for testosterone detection in serum samples

A new immunofiltration assay for testosterone is proposed. During the first step of the assay, testosterone molecules in serum samples compete in solution with the testosterone-peroxidase conjugate for interaction with anti-testosterone antibodies pre-bound to the conjugate between staphylococcal protein A and polymethacrylate polyanion. The reaction mixture is then filtered through a membrane charged with immobilized poly(N-ethyl-4-vinylpyridinium) polycation. The filtration is accompanied by a rapid separation of the polyanion containing complexes due to high-affinity electrostatic interactions. Following removal of unbound compounds the immobilized peroxidase is detected using a substrate that produces an insoluble coloured product. The proposed assay has been shown to combine high speed (20 min) and sensitivity (0.1 ng ml(-1)), and to be applicable for out-of-laboratory conditions. Based on densitometric measurements, the RSD of the assay is calculated to be 3.2-5.1% (n = 4). The proposed assay is 4 times faster than the microplate enzyme immunoassay (ELISA) based on the same immunoreagents. Pre-incubation of the antibody and the polyanion-protein A conjugate at a certain ratio excludes the influence of immunoglobulins from the tested serum samples on the assay results. The polyanion-protein A conjugate can be used as a universal reagent, eliminating the necessity to modify specific antibodies for each immunoassay.     

Investigation of the influence of the conditions during recrystallization annealing on the plasticity of molybdenum-base alloys with low concentrations of additives

An investigation was made of the conditions during recrystallization annealing on the plasticity and the nature of fracture of Mo-base alloys containing zirconium or titanium (TSM-4, TsM-6, Mo-Ti-C) and alloys free of active oxide-forming elements (TSM-3). Annealing at T > T_recr took place under traditional conditions employed in heat treatments (in 10^–4–10^–6 torr vacuum, in hydrogen-filled furnaces) or under conditions ensuring minimal saturation of the alloys with oxygen during heat treatments (this involved preliminary outgassing vacuum furnaces and wrapping of the samples in molybdenum foil) or under conditions of controlled partial oxygen pressure (in the presence of the Al₂O₃ powder in the annealing zone). The degree of saturation of the alloys with oxygen was deduced from the appearance of zirconium or titanium oxide in the surface layers of the alloys containing these elements. The results indicated that the conditions during heat treatment and alloying of molybdenum with zirconium and titanium had an important influence on the plasticity and fracture of the Mo-base alloys. The results obtained were analyzed on the basis of the ideas on intergranular brittleness in bcc materials because of segregation of oxygen at grain boundaries and a refining influence of zirconium and titanium on the Mo alloys saturated with oxygen, involving binding of the oxygen in oxides and thus preventing its segregation at grain boundaries.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 93–99, August, 1980.     

Properties of Micellar Solutions of Sodium Decyl Sulfate at Relatively High Concentrations

Russian Journal of Physical Chemistry A - Heat capacities of aqueous solutions of anionic surfactant sodium decyl sulfate in the 0.28–0.42&nbsp;mol&nbsp;kg−1 range of molar...     

Modeling of Phase Shifts of Light in Orders of Diffraction Gratings of an Interference Linear Displacement Sensor

Optics and Spectroscopy - Phase shifts of light in orders of diffraction grating for the interference linear displacement sensor are considered. Using the phase diffraction grating with given...