Ways to Reach Lower Detection Limits of Lateral Flow Immunoassays

This chapter considers factors influencing sensitivity of lateral flow immunoassay and modern developments that are focused on reaching lower detection limits. The existing variety of proposed approaches is classified in accordance with the “big five rules” for these assays, including proper sample, receptor, interaction, response, and output. The solutions for rapid extraction of target analytes and preventing negative influence of extractants are considered. Role to antibodies affinity and specificity is characterized. Potential of alternate bioreceptor molecules is discussed. Immunoreactants’ compositions, concentrations, and locations on the test strip are characterized as factors determining assay parameters. The existing variety of labels is compared in terms of their optical and alternate registration. Tools to modulate a sequence of analytical reactions and to form aggregates of the detected labels are considered. The discussed approaches are illustrated through developments of test strips for detection of mycotoxins, veterinary drugs, and other analytes

APPLICATION OF AMINOPHENYLBORONIC ACID CONJUGATED WITH PROTEIN CARRIER FOR APTACHROMATOGRAPHIC DETECTION OF LEAD IONS

This work was financially supported by Russian Science Foundation (project # 19-44-02020)

Molecular genetic methods for identifying raw materials in meat products: Diversity, opportunities and prospects

In the current economic situation, after easing the Covid pandemic restrictions, almost all laboratories, which are focused on evaluation of the conformity of food products, have faced issues in supplying for their laboratories. In this regard, in the last years many laboratories have been forced to validate new approaches and introduce new methods for assessing conformity of the food products. Very often it is not possible to use only one method to resolve the issue of the food product ingredients, especially for the purpose of traceability of their names and the used raw materials, listed on the label. Survey of the raw food materials to determine whether they correspond to the type name is a simpler task, in contrast to survey of the multicomponent food product. Many researchers have to estimate the opportunities and feasibility of application of various methodologies in their workplaces. Therefore, this review is relevant for the researchers in this field, as it focuses on aspects and special features of similar methodologies. The prospect of molecular genetic methods for identification of the raw materials used for manufacturing of meat products is presented below. This review also represents characteristics of methods for identification of the sources of raw materials used for the manufacturing of the meat products, based on the recognition of species-specific sections within the nucleic acids structures. The variety of methods (hybridization methods, polymerase chain reaction, different types of isothermal amplifications, methods using CRISPR/Cas systems), the principles of their implementation, and achieved analytical characteristics are considered. The capacities and competitive potential of various methods are discussed, as well as approaches being developed to overcome the existing limitations.In the current economic situation, after easing the Covid pandemic restrictions, almost all laboratories, which are focused on evaluation of the conformity of food products, have faced issues in supplying for their laboratories. In this regard, in the last years many laboratories have been forced to validate new approaches and introduce new methods for assessing conformity of the food products. Very often it is not possible to use only one method to resolve the issue of the food product ingredients, especially for the purpose of traceability of their names and the used raw materials, listed on the label. Survey of the raw food materials to determine whether they correspond to the type name is a simpler task, in contrast to survey of the multicomponent food product. Many researchers have to estimate the opportunities and feasibility of application of various methodologies in their workplaces. Therefore, this review is relevant for the researchers in this field, as it focuses on aspects and special features of similar methodologies. The prospect of molecular genetic methods for identification of the raw materials used for manufacturing of meat products is presented below. This review also represents characteristics of methods for identification of the sources of raw materials used for the manufacturing of the meat products, based on the recognition of species-specific sections within the nucleic acids structures. The variety of methods (hybridization methods, polymerase chain reaction, different types of isothermal amplifications, methods using CRISPR/Cas systems), the principles of their implementation, and achieved analytical characteristics are considered. The capacities and competitive potential of various methods are discussed, as well as approaches being developed to overcome the existing limitations

LATERAL FLOW TEST STRIPS FOR HG2+ IONS DETECTION BASED ON COMBINATION OF OLIGONUCLEOTIDE-MODIFIED GOLD NANOPARTICLES AND CHELATION BY GLUTATHIONE

The environment requires special attention due to the development of the industry, the transition to industrial automation, battery use and human waste disposal. At the same time, the development of analytical test systems makes it possible to determine the content of various contaminants and regulate their entry into the surrounding world. However, a number of toxic contaminants can accumulate in the environment (water, soil) and cause long-term toxic effects on living organisms, including humans. Therefore, the analytical techniques being developed (colorimetric, electrochemical, chromatographic etc.) and the laboratory methods (ICP-MS, ICP-AES) of their analysis existing in practice are in demand.This work was financially supported by Russian Science Foundation (project # 19-44-02020)

Сomparison of Au, Au-Pt, and Au-Ag nanoparticles as markers for immunochromatographic determination of nonylphenol

Gold spherical nanoparticles, gold-platinum nanoflowers, and gold-silver nanostars were obtained and compared as labels for immunochromatographic analysis. The nanoparticles were synthesized by chemical reduction from various precursors and then conjugated with staphylococcal protein A to be used in indirect immunochromatographic determination of nonylphenol. The results obtained were evaluated in terms of analytical characteristics and R2 value, as well as the color intensity of the test band. According to the comparison results, it was revealed that the R2 value varied from 0.82 for the gold-silver nanostars to 0.96 for the spherical gold nanoparticles. The working range of determined concentrations was from 2 to 100 μg/mL for unspherical and from 2 to 50 μg/mL – for spherical markers used; the analysis time was 20 min

COMPARISON OF Au, Au-Pt, AND Au-Ag NANOPARTICLES AS MARKERS FOR THE IMMUNOCHROMATOGRAPHIC DETERMINATION OF NONYLPHENOL

This work was supported by the Russian Science Foundation (grant no. 22-13-00293)

Neutron Thermal Cross Sections, Westcott Factors, Resonance Integrals, Maxwellian Averaged Cross Sections and Astrophysical Reaction Rates Calculated from Major Evaluated Data Libraries

We present calculations of neutron thermal cross sections, Westcott factors, resonance integrals, Maxwellian-averaged cross sections and astrophysical reaction rates for 843 ENDF materials using data from the major evaluated nuclear libraries and European activation file. Extensive analysis of newly-evaluated neutron reaction cross sections, neutron covariances, and improvements in data processing techniques motivated us to calculate nuclear industry and neutron physics quantities, produce s-process Maxwellian-averaged cross sections and astrophysical reaction rates, systematically calculate uncertainties, and provide additional insights on currently available neutron-induced reaction data. Nuclear reaction calculations are discussed and new results are presented.Comment: 145 pages, 15 figures, 19 table

Production of polyclonal antibodies and development of fluorescence polarization immunoassay for sulfanilamide

N-sulfanil-4-aminobutyric acid (SAB), which mimics common parts of the sulfonamides' structure, was synthesized and used to produce antibodies to sulfanilamide. Rabbit polyclonal antibodies have been raised using SAB conjugates with ovalbumin (OVA) or soybean trypsin inhibitor (STI). The immunogen based on SAB-STI could yield higher affinity anitbodies against sulfanilamide. The same SAB derivative was used for synthesis of a fluorescein-labeled tracer with fluorescein-thiocarbamyl ethylendiamine. A fluorescence polarization immunoassay (FPIA) for sulfanilamide was developed. The limits of detection sulfanilamide were 0.07, 0.10, and 0.07 μg mL -1 for water, diluted milk, and precipitated milk samples, respectively. The developed FPIA exhibited sensitivities below the respective maximal residue limits (MRLs) for individual sulfonamides (0.1 μg mL -1). The coefficients of variation of results for milk samples were lower than 5%. Total time for simple sample pretreatment and measurement is about 10 min for one sample. High cross-reactivity with sulfaguanidine (96%), sulfamethoxypyridazine (75%), and sulfachloropyridazine (28%), which have planar structures, could be suitable for simultaneous detection of these sulfa drugs in milk and developed fluorescence polarization immunoassay could be classified as a group-selective assay. Copyright © Taylor & Francis, Inc

Highly Sensitive Immunochromatographic Identification of Tetracycline Antibiotics in Milk

A rapid immunochromatographic assay was developed for the control of tetracycline (TC). The assay is based on the competition between immobilized TC-protein conjugate and TC in a tested sample for binding with polyclonal anti-TC antibodies conjugated to colloidal gold during the flow of the sample along a membrane strip with immobilized reactants. Conjugation of colloidal gold and the total immunoglobulin (IgG) fraction of polyclonal antibodies was used to increase the assay sensitivity to ensure low content of specific antibodies in the conjugate. This allowed effective inhibition of free TC and conjugate binding in the strip test zone. Photometric marker registration allows control of the reduction of binding, thereby enhancing detection sensitivity. The proposed assay allows TC to be detected at concentrations up to 20 ng/mL, exceeding the limit of detection of the known analogues, in a wide working range (more than two orders) of 60 pg/mL to 10 ng/mL, ensured through the use of polyclonal antibodies. The assay time is 10 min. The efficiency of the designed assay is shown to identify TC in milk; the degree of recovery of TC ranges from 90 to 112%. The precision of the concentrations measurements was no more than 10%

Human DNA mismatch repair: coupling of mismatch recognition to strand-specific excision

Eukaryotic mismatch-repair (MMR) proteins MutSα and MutLα couple recognition of base mismatches to strand-specific excision, initiated in vivo at growing 3′ ends and 5′ Okazaki-fragment ends or, in human nuclear extracts, at nicks in exogenous circular substrates. We addressed five biochemical questions relevant to coupling models. Excision remained fully efficient at DNA:MutSα ratios of nearly 1 to 1 at various mismatch-nick distances, suggesting a requirement for only one MutSα molecule per substrate. As the mismatch-nick DNA contour distance D in exogenous substrates increased from 0.26 to 0.98 kbp, initiation of excision in extracts decreased as D−0.43 rather than the D−1 to D−2 predicted by some translocation or diffusion models. Virtually all excision was along the shorter (3′–5′) nick-mismatch, even when the other (5′–3′) path was less than twice as long. These observations argue against stochastically directed translocating/diffusing recognition complexes. The failure of mismatched DNA in trans to provoke excision of separate nicked homoduplexes argues against one-stage (concerted) triggering of excision initiation by recognition complexes acting through space. However, proteins associated with gapped DNA did appear to compete in trans with those in cis to mismatch-associated proteins. Thus, as in Escherichia coli, eukaryotic MMR may involve distinct initial-activation and excision-path-commitment stages