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Recently, urinary tract infection (UTI) triggered by bacteria carrying pan-drug-resistant genes, including carbapenem resistance gene blaNDM and blaKPC, colistin resistance gene mcr-1, and tet(X) for tigecycline resistance, have been reported, posing a serious challenge to the treatment of clinical UTI. Therefore, point-of-care (POC) detection of these genes in UTI samples without the need for pre-culturing is urgently needed. Based on PEG 200-enhanced recombinase polymerase amplification (RPA) and a refined Chelex-100 lysis method with HRP-catalyzed lateral flow immunoassay (LFIA), we developed an MCL-PRPA-HLFIA cascade assay system for detecting these genes in UTI samples. The refined Chelex-100 lysis method extracts target DNA from UTI samples in 20 min without high-speed centrifugation or pre-incubation of urine samples. Following optimization, the cascade detection system achieved an LOD of 102 CFU/mL with satisfactory specificity and could detect these genes in both simulated and actual UTI samples. It takes less than an hour to complete the process without the use of high-speed centrifuges or other specialized equipment, such as PCR amplifiers. The MCL-PRPA-HLFIA cascade assay system provides new ideas for the construction of rapid detection methods for pan-drug-resistant genes in clinical UTI samples and provides the necessary medication guidance for UTI treatment. [ABSTRACT FROM AUTHOR]

Phenylethanolamine A (PEAA), as a typical β2-adrenoceptor agonist (β-AA), was widely illegally used in feed to improve the lean meat ratio. The detection performance of immunoassay, which is one of the effective methods to monitor PEAA residues in animal urine, has been hindered by high concentration of salt. Herein, we produced one highly salt-tolerant monoclonal antibody (mAb) 3E2 by hybridoma technology. Homologous modelling and molecular docking were used to analyse the antibody salt tolerance mechanism. Results show that the tight hydrophobic binding cavity is the key to high tolerance. Then the mAb 3E2 was used for specific detecting PEAA by enzyme-linked immunosorbent assay (ELISA) with the IC50 value of 0.36 ng mL−1and the LOD value of 0.065 µg L−1. Benefiting from the high salt tolerance of antibodies, swine urine and sheep urine spiked with PEAA can be detected directly by ELISA, and the acceptable recovery rates of 80.1–108.8% were obtained. [ABSTRACT FROM AUTHOR]

To monitor the contamination of a type A trichothecene, diacetoxyscirpenol (DAS), one monoclonal antibody (mAb) 8A9 with high affinity and specificity was prepared in the present study. The mAb 8A9 showed a 50% inhibition concentration (IC50) of 0.31 μg/L, which is of the highest affinity reported to date. An indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and lateral flow immunoassay (LFIA) based on mAb 8A9 were developed and exhibited limits of detection as low as 0.65 μg/kg and 100 μg/kg in rice samples, respectively. The molecular recognition mechanism of mAb 8A9 to DAS was explored by molecular docking. The results showed that the hydrophobic amino acids of mAb 8A9 interacted with DAS by forming hydrogen bonds and a pi-sigma bond, which lead to a highly specific recognition of DAS. In summary, we produced one mAb, developed ELISA and LFIA for DAS detection in rice with significantly sensitivity, specificity, accuracy, and precision. [ABSTRACT FROM AUTHOR]

Nitrofurans comprise a class of synthetic broad-spectrum antibacterial agents, which had been used extensively as therapeutic drugs and feed additives in animal husbandry. Because of the potential carcinogenic and mutagenic effects of these drugs and their metabolites, most countries have banned their use in food animals. However, driven by economic interests, the illegal use of nitrofurans poses a significant threat to human health. Therefore, to safeguard health of the consumer, it is of paramount importance to develop efficient, sensitive, and reliable detection methods to monitor nitrofuran and their metabolite residues in animal-derived foods. In this paper, the progress in immunoassays for nitrofuran residues is reviewed, including enzyme-linked immunosorbent assay, fluoroimmunoassay, chemiluminescence immunoassay, immunochromatography, and immunosensor assay. Basic principles and applications of these methods were described and compared in this paper. Furthermore, the future perspective on the improvement and development of the immunoassays for the detection of nitrofurans has been discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A chemical-staining (crystal violet) based lateral flow immunoassay (LFIA) is first proposed for small molecule detection. • The developed LFIA significantly simplify the assay behavior and conquer the intrinsic limitations of nanomaterials labels. • The LFIA were successfully applied in several food samples for furazolidone detection. Abstract The nanomaterials based lateral flow immunoassays (LFIAs) have been widely used for on-site detection of small molecules contaminants. Nevertheless, their practical applications are often constrained by the complicated materials synthesis and surface modification process of nanomaterials. Herein, inspired by chemical-staining, a crystal violet (CV) staining based LFIAs was innovatively developed for the first time to analyze small molecules contaminant with significantly simplified behaviour and surpassing repeatability. This nanomaterials-free technique overcomes the intrinsic limitations of nanomaterials, owing to the superior protein dye property of CV. To demonstrate the feasibility of the unique strategy, furazolidone (FZD) was used as a model analyte, results showed detection limits of as low as 7 and 1.53 ng mL−1 by visual observation and quantitative analysis, respectively. Finally, to validate its applicability in actual conditions, the platform is well applied in three kinds of food samples (shrimp, fish and pork). Furthermore, as the detection principle is based on the molecular recognition between antigen and antibody, our method may find general applications by staining other antibodies against other target analytes. [ABSTRACT FROM AUTHOR]

Abstract: Local hypoxia in tumors results in undesirable impediments for the efficiencies of oxygen‐dependent chemical and photodynamic therapy (PDT). Herein, a versatile oxygen‐generating and pH‐responsive nanoplatform is developed by loading MnO2 nanodots onto the nanosystem that encapsulates g‐C3N4 and doxorubicin hydrochloride to overcome the hypoxia‐caused resistance in cancer therapy. The loaded MnO2 nanodots can react with endogenous acidic H2O2 to elevate the dissolved oxygen concentration, leading to considerably enhanced cancer therapy efficacy. As such, the as‐prepared nanoplatform with excellent dispersibility and satisfactory biocompatibility can sustainably increase the oxygen concentration and rapidly release the encapsulated drugs in acid H2O2 environment. In vitro cytotoxicity experiments show a higher therapy effect by the designed nanoplatform, when compared to therapy without MnO2 nanodots under hypoxia condition, or chemical and photodynamic therapy alone with the presence of MnO2 nanodots. In vivo experiments also demonstrate that 4T1 tumors can be very efficiently eliminated by the designed nanoplatform under light irradiation. These results highlight that the MnO2 nanodots‐based nanoplatform is promising for elevating the oxygen level in tumor microenvironments to overcome hypoxia limitations for high‐performance cancer therapy. [ABSTRACT FROM AUTHOR]

Theoretically, sandwich immunoassay is more sensitive and has a wider working range than that of competitive format. However, it has been thought that small molecules cannot be detected by the sandwich format due to their limited size. In the present study, we proposed a novel strategy for achieving sandwich immunoassay of β-lactams with low molecular weights. Firstly, five β-lactam antibiotics were selected to bind with penicillin binding protein (PBP)2x* to form complexes. Then, monoclonal and polyclonal antibodies against PBP2x*-β-lactams complexes were produced by animal immunization. Subsequently, the optimal pairing antibodies were utilized to establish sandwich immunoassay for detection of 18 PBP2x*-β-lactam complexes. Among them, ceftriaxone could be detected at as low as 1.65 ng/mL with working range of 1–1000 ng/mL in milk. To reveal the detection mechanism, computational chemistry and molecular recognition study were carried out. The results showed that β-lactams with a large size and complex structures maybe conducive to induce conformational changes of PBP2x*, and then exhibit greater possibility of being detected by sandwich immunoassay after combination with PBP2x*. This study provides insights for subsequent investigations of anti-metatype antibody screening and sandwich immunoassay establishment for small-molecule detection. [ABSTRACT FROM AUTHOR]