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Contamination of the environment by technogenic endocrine disrupting compounds (EDCs) becomes serious threat to public health. To effectively prevent this threat, it is necessary to improve analytical methods for EDCs to ensure mass, fast and productive monitoring. In the given work, a dual lateral flow test (LFT) is developed in the first time for simultaneous immunodetection of bisphenol A and dimethyl phthalate, priority EDCs releasing from plastic and belonging to different chemical classes. It combines integrated detection of two EDCs by one analytical system with rapidity and simplicity of LFTs allowing for off-lab testing without additional reagents and devices. Gold nanoparticles differing in shape and color (red gold nanospheres and blue gold nanoflowers) are applied as markers to simplify interpretation of the obtained results. Under the optimal conditions chosen for efficient control of the both analytes, the detection limits of bisphenol A and dimethyl phthalate are 0.67 ng/mL and 2.22 ng/mL, respectively. Time of the assay is 15 min. The proposed dual LFT has confirmed its practical applicability by analyzing natural water samples with recovery of bisphenol A and dimethyl phthalate in the ranges of 90.4-107.0% and 86.8-118.0%, respectively., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

A bimetallic core-shell-shell nanorods structure with gap-embedded Raman reporter 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB) was developed and applied as a SERS-active nanotag in surface-enhanced Raman scattering lateral flow immunoassay (SERS-LFIA) of the insecticide fipronil. Due to the strong SERS signal of the Au DTNB @Ag DTNB @AgNRods, fipronil is detected with extremely low detection limit of 4.6 pg/mL. To the best of our knowledge, the proposed technique is the first SERS-LFIA of fipronil, proven to be effective in the selective determination of the target analyte and capable of detecting fipronil in a matrix of food samples (cucumber and apple juice) with recoveries of 97.0-117.0%. Moreover, the applied functionalization of the SERS nanotag with anti-species antibodies has provided a versatile immunoprobe that could improve performance of different LFIAs., Competing Interests: Declarations Conflict of interest The authors have no relevant financial or non-financial interests to disclose.The authors have no conflicts of interest to declare that are relevant to the content of this article.All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.The authors have no financial or proprietary interests in any material discussed in this article., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

When developing immunochemical test systems, it is necessary to obtain specific antibodies. Their quality depends, among other things, on the immunogen used. When preparing hapten-protein conjugates to obtain antibodies for low-molecular-weight compounds, the key factors are the structure of the hapten itself, the presence of a spacer, the size of the carrier protein and the degree of its modification by hapten molecules. This work shows that one additional factor-the conditions for obtaining the hapten-protein conjugate-is overlooked. In this work, we have synthesized conjugates of bisphenol A derivative 4,4-bis(hydroxyphenyl)valeric acid (BVA), the protein carrier soybean trypsin inhibitor (STI), and bovine serum albumin (BSA) in reaction media combining water with two organic solvents: dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). Namely, BSA DMF -BVA, STI DMF -BVA, BSA DMSO -BVA and STI DMSO -BVA conjugates were obtained. Rabbit polyclonal antibodies against the BSA DMF -BVA conjugate demonstrated basically different interactions in the developed ELISA systems using either STI DMF -BVA or STI DMSO -BVA conjugates. The use of the STI DMF -BVA conjugate demonstrated the absence of competition in combination with antisera obtained from BSA DMF -BVA in an ELISA. A competitive interaction was observed only with the use of the STI DMSO -BVA conjugate. Under the selected conditions, the detection limit of bisphenol A was 8.3 ng/mL, and the working range of determined concentrations was 18.5-290.3 ng/mL. The obtained data demonstrate the possibility of achieving sensitive immunoassays by simply varying the reaction media for the hapten-protein conjugation, which could provide an additional tool in the development of immunoassays for other low-molecular-weight compounds.

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool and an up-to-date method of analytical chemistry due to its high sensitivity and fingerprint recognition capabilities. Nowadays SERS due to its label-free detection capabilities is being actively developed in medical fields, for example in the analysis of biologically important substances in different matrixes, for potential on-site detection of toxic substances, food safety, and so on. To get the SERS signal, it is necessary the presence of plasmonic nanostructures in the SERS substrates. Electrospun nanofibers have been an attractive alternative to SERS-platforms due to the diversity of advantages, including ease of preparation, structure flexibility, and others. In this review, we summarized the methods of plasmonic nanostructures incorporating substrate based on electrospun nanofibers. Also, the analytical application of SERS-active electrospun nanofibers with embedded nanostructures focused on biologically significant molecules is observed in detail. Finally, the future outlook in the application of these substrates in bioanalysis as the most promising area in analytical chemistry is presented.

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 Sb 3+ detection was developed. The biotinylated aptamer A 10 was hybridized with its complementary biotinylated oligonucleotide T 10 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. Sb 3+ presenting in the sample bounded to an A 10 aptamer, thus releasing T 10 , preventing streptavidin-HRP binding and, as a result, reducing the optical signal. This effect allowed for the detection of Sb 3+ 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 A 10 /T 10 complex formation promoted dehybridization of the aptamer A 10 and the formation of the A 10 /Sb 3+ complex. The working range of the Ag + -enhanced microplate apta-enzyme assay for Sb 3+ 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 Sb 3+ in the range of 109.0-126.2% and 99.6-106.1%, respectively.

Surface-enhanced Raman scattering (SERS) is considered an efficient technique providing high sensitivity and fingerprint specificity for the detection of pesticide residues. Recent developments in SERS-based detection aim to create flexible plasmonic substrates that meet the requirements for non-destructive analysis of contaminants on curved surfaces by simply wrapping or wiping. Herein, we reported a flexible SERS substrate based on cellulose fiber (CF) modified with silver nanostructures (AgNS). A silver film was fabricated on the membrane surface with an in situ silver mirror reaction leading to the formation of a AgNS-CF substrate. Then, the substrate was decorated through in situ synthesis of raspberry-like silver nanostructures (rAgNS). The SERS performance of the prepared substrate was tested using 4-mercaptobenzoic acid (4-MBA) as a Raman probe and compared with that of the CF-based plasmonic substrates. The sensitivity of the rAgNS/AgNS-CF substrate was evaluated by determining the detection limit of 4-MBA and an analytical enhancement factor, which were 10 nM and ~10 7 , respectively. Further, the proposed flexible rAgNS/AgNS-CF substrate was applied for SERS detection of malathion. The detection limit for malathion reached 0.15 mg/L, which meets the requirements about its maximum residue level in food. Thus, the characteristics of the rAgNS/AgNS-CF substrate demonstrate the potential of its application as a label-free and ready-to-use sensing platform for the SERS detection of trace hazardous substances.

The use of a large amount of toxic synthetic materials leads to an increase in the pollution of environmental objects. Phthalates are compounds structurally related to esters of phthalic acid that are widely used in the manufacturing of synthetic packaging materials as plasticizers. Their danger is conditioned by leaching into the environment and penetrating into living organisms with negative consequences and effects on various organs and tissues. This work presents the first development of lateral flow immunoassay to detect dibutyl phthalate, one of the most common representatives of the phthalates group. To form a test zone, a hapten-protein conjugate was synthesized, and gold nanoparticles conjugated with antibodies to dibutyl phthalate were used as a detecting conjugate. The work includes the preparation of immunoreagents, selectivity investigation, and the study of the characteristics of the medium providing a reliable optical signal. Under the selected conditions for the analysis, the detection limit was 33.4 ng/mL, and the working range of the determined concentrations was from 42.4 to 1500 ng/mL. Time of the assay-15 min. The developed technique was successfully applied to detect dibutyl phthalate in natural waters with recovery rates from 75 to 115%.

Aptamer selection against novel infections is a complicated and time-consuming approach. Synergy can be achieved by using computational methods together with experimental procedures. This study aims to develop a reliable methodology for a rational aptamer in silico et vitro design. The new approach combines multiple steps: (1) Molecular design, based on screening in a DNA aptamer library and directed mutagenesis to fit the protein tertiary structure; (2) 3D molecular modeling of the target; (3) Molecular docking of an aptamer with the protein; (4) Molecular dynamics (MD) simulations of the complexes; (5) Quantum-mechanical (QM) evaluation of the interactions between aptamer and target with further analysis; (6) Experimental verification at each cycle for structure and binding affinity by using small-angle X-ray scattering, cytometry, and fluorescence polarization. By using a new iterative design procedure, structure- and interaction-based drug design (SIBDD), a highly specific aptamer to the receptor-binding domain of the SARS-CoV-2 spike protein, was developed and validated. The SIBDD approach enhances speed of the high-affinity aptamers development from scratch, using a target protein structure. The method could be used to improve existing aptamers for stronger binding. This approach brings to an advanced level the development of novel affinity probes, functional nucleic acids. It offers a blueprint for the straightforward design of targeting molecules for new pathogen agents and emerging variants., (© 2022 Wiley-VCH GmbH.)

Detection of lead (II) in water sources is of high importance for protection from this toxic contaminant. This paper presents the development and approbation of a lateral flow test strip of lead (II) with the use of phenylboronic acid as chelating agent and oligocytosine chain as receptor for the formed complexes. To locate the bound lead (II) on the test strip, phenylboronic acid was conjugated with carrier protein (bovine serum albumin) and applied as a binding line. In turn, the oligocytosine was conjugated with gold nanoparticle to provide coloration of the finally formed complexes (bovine serum albumin - phenylboronic acid - lead (II) - oligocytosine - gold nanoparticle). This combination of two binding molecules provides the «sandwich » assay with direct dependence of label binding from the analyte content. The technique is characterized by high sensitivity (0.05 ng mL -1 ) and the absence of cross-reactions with other metal ions which are often satellite in natural waters. The developed lateral flow tests were successfully applied for lead (II) detection in water. Time of the assay was 5 min. The reached parameters confirm efficiency of the proposed technique for rapid and non-laborious testing under nonlaboratory conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The development of analytical methods for the determination of metal ions in water is one of the priority tasks for efficient environmental monitoring. The use of modified gold nanoparticles and the colorimetric detection of their aggregation initiated by ions binding with specific receptors on the nanoparticle surface has high potential for simple testing. However, the limits of this approach and the parameters determining the assay sensitivity are not clear, and the possibilities of different assay formats are estimated only empirically. We have proposed a mathematical description of the aggregation processes in the assay and have estimated the detection limits of an aptamer-based assay of Pb2+ ions theoretically and experimentally. In the studied assay, gold nanoparticles modified with G,T-enriched aptamer were used, and their aggregation caused by the interaction with Pb2+ ions was controlled via a color change. The experimentally determined limit of Pb2+ detection was 700 ppb, which was in good agreement with theoretical calculations. An examination of the model showed that the limiting parameter of the assay is the binding constant of the aptamer-Pb2+ ion interaction. To overcome this limitation without searching for alternate receptors, two methods have been proposed, namely additional aggregation-causing components or centrifugation. These approaches lowered the detection limit to 150 ppb and even to 0.4 ppb. The second value accords with regulatory demands for the permissible levels of water source contamination, and the corresponding approach has significant competitive potential due to its rapidity, simple implementation, and the visual assessment of the assay results.

This review presents the state-of-the-art of optical sensors for determination of biogenic amines (BAs) in food by publications covering about the last 10 years. Interest in the development of rapid and preferably on-site methods for quantification of BAs is based on their important role in implementation and regulation of various physiological processes. At the same time, BAs can develop in different kinds of food by fermentation processes or microbial activity or arise due to contamination, which induces toxicological risks and food poisoning and causes serious health issues. Therefore, various optical chemosensor systems have been devised that are easy to assemble and fast responding and low-cost analytical tools. If amenable to on-site analysis, they are an attractive alternative to existing instrumental analytical methods used for BA determination in food. Hence, also portable sensor systems or dipstick sensors are described based on various probes that typically enable signal readouts such as photometry, reflectometry, luminescence, surface-enhanced Raman spectroscopy, or ellipsometry. The quantification of BAs in real food samples and the design of the sensors are highlighted and the analytical figures of merit are compared. Future instrumental trends for BA sensing point to the use of cell phone-based fully automated optical evaluation and devices that could even comprise microfluidic micro total analysis systems.