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Nicotine (NCT) is commonly contained in e-cigarette oils, and long-term nicotine intake can exacerbate cardiovascular disease, neurodegenerative disease, and lung cancer. Therefore, there is a need to develop a fast and sensitive method for detecting NCT in e-cigarette oils. We prepared anti-NCT monoclonal antibodies (mAbs), which belong to the IgG2 subclass. The optimum mAb had a half-maximal inhibitory concentration (IC 50) of 6.81 ng/mL for NCT. We developed a colloidal gold immunochromatographic strip (CG-ICS) to detect NCT content with a visual cut-off and limit of detection of 20 ng/mL and 0.40 ng/mL, respectively. The recovery rates of NCT from spiked samples ranged between 100.36% and 109.96% based on CG-ICS. These results were consistent with those obtained from high performance liquid chromatography (HPLC). We confirmed the reliability of CG-ICS using NCT-positive samples. Therefore, CG-ICS represents an effective and rapid on-site screening tool for the detection of NCT in e-cigarette oils. • Anti-NCT mAbs were prepared, which had a IC 50 of 6.81 ng/mL for NCT. • CG-ICS was developed to detect NCT content with a visual cut-off and LOD of 20 ng/mL and 0.40 ng/mL, respectively. • The recovery rates of NCT from spiked samples ranged between 100.36% and 109.96% based on CG-ICS. • These results were consistent with those obtained from HPLC. [ABSTRACT FROM AUTHOR]

Thymidine kinase 1 (TK1) is a marker of cell proliferation that can be used for early screening, treatment monitoring, and evaluating the prognosis of patients with tumors. The main purpose of this study was to develop clinically applicable TK1 antibodies, establish an appropriate detection method, and provide material and technical support for the research and clinical application for different types of tumors. Experimental mice were immunized with the C-terminal 31 peptide of human TK1 to screen monoclonal cell lines capable of stably secreting specific antibodies. Monoclonal antibodies were then prepared, purified and screened for optimal pairing following the identification of purity and isotype. Finally, based on the principles adopted by the double-antibody sandwich detection method, we constructed a lateral flow immunochromatographic assay (LFIA) to quantify the concentration of TK1 in serum samples when using a gold nanoparticle-labeled anti-TK1 monoclonal antibody as a probe. The limit of detection for TK1 in serum was 0.31 pmol/L with a detection range of 0.31–50 pmol/L. The spiked recoveries ranged from 97.7% to 109.0% with an analytical precision of 5.7–8.2%; there was no cross-reactivity with common proteins in the serum. The established LFIA also exhibited good consistency with commercially available chemiluminescent immunoassay kits for the detection of clinical samples. The LFIA developed in this study has the advantages of high sensitivity, accuracy, reproducibility and strong specificity, and provides a new technical tool for the quantitative detection of TK1. • Material and technical support for the clinical detection of different tumors. • LFIA was set up to quantify the concentration of TK1 in serum samples. • The ultrasensitive LOD was 0.31 pmol/L with a detection range of 0.31–50 pmol/L. • LFIA exhibited good consistency with CLIA for the detection of clinical samples. [ABSTRACT FROM AUTHOR]

Abstract: A competitive enzyme-linked immunosorbent assay (ELISA) was developed for the quantitative detection of the hexoestrol (HES). Polyclonal rabbit antisera, raised against protein conjugate hexoestrol-mono-carboxyl-propyl-ethyl-bovine-serum-albumin (HES-MCPE-BSA), were utilized in immobilized antibody-based and competitive immunoassays. Assay conditions, including concentrations of antisera and Horseradish peroxidase (HRP)–HES were optimized. The effect of incubation time, surfactant concentration, ionic strength and pH of the medium were also investigated. The typical calibration curve gave an average IC50 value of 2.4ng/ml, calibration range from 0.2ng/ml to 30.5ng/ml and a detection limit of 0.07ng/ml. The specificity of the assay was tested against HES structurally related compounds, and the assay proved highly selective for HES. Assay performance was validated by using spiked pork and liver tissues samples. Moreover, it was compared with liquid chromatography–tandem mass spectrometry. The ion pair for quantification of HES was 269.4/134, and linear equation of HES was Y =0.2148X −0.0374 (r =0.9993). The two analytical methods can be applied to monitor HES and other steroid residues in edible foods. [Copyright &y& Elsevier]

An anti-phenolphthalein monoclonal antibody (mAb) was prepared based on the N,N′-Carbonyldiimidazole (CDI) method through phenolphthalein conjugated with proteins. Indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and colloidal gold-based immunochromatographic assay (ICA) methods were used to determine phenolphthalein in slimming products. A standard curve was established, and the IC 50 and limit of detection of ic-ELISA were 0.95 and 0.10 ng/mL with a linear detection range of 0.27–3.37 ng/mL. The developed ICA was used to detect phenolphthalein in tablets, capsules, and slimming tea samples with visual limit of detection values of 10 μg/kg, and cut-off values of 200 μg/kg. The results indicated that these two methods could be used to quickly detect phenolphthalein in slimming products. Colloidal gold-based ICA methods were developed to determine phenolphthalein in slimming products. The developed ICA strip was used to detect phenolphthalein in tablets, capsules, and slimming tea samples with visual limit of detection values of 10 μg/kg, and cut-off values of 200 μg/kg. [Display omitted] • A sensitive anti-phenolphthalein monoclonal antibody (mAb) was fabricated. • ic-ELISA and the ICA strip methods were developed to determine phenolphthalein. • The visual limit of detection and cut-off values of the ICA were 10 and 200 μg/kg. [ABSTRACT FROM AUTHOR]

• A highly sensitive anti-2,4-D MAb was prepared for the rapid detection. • Ic-ELISA and Immunochromatographic assay (ICS) were developed. • The application of ICS in real samples was demonstrated to be feasible. • The method was rapid, easy to operate and provided visible detection results. The compound 2,4-dichlorophenoxyacetic acid (2,4-D) is a synthetic plant growth regulator, which is widely used in agricultural production. Consequently, it is necessary to establish a rapid and sensitive detection method to monitor its use and prevent the environmental and human health problems caused by overuse. In this study, a monoclonal antibody (mAb) 2D5 against 2,4-D was prepared, and based on it, an ic-ELISA and an immunochromatographic strip assay (ICA) were developed for rapid detection. The 50% inhibitory concentration (IC 50) of the mAb against 2,4-D was 1.7 ng mL−1 and the mAb showed no cross-reactivity with other plant growth regulators with similar structures to 2,4-D. Under optimum conditions, the ICA showed a visual detection limit (vLOD) of 20 ng mL−1 and a cut-off value of 200 ng mL−1 in bean sprouts, and cabbage samples gave the same results. The quantitative detection showed the linear detection ranges for bean sprouts and cabbage samples were 6.3–73.0 and 5.4–132.6 ng mL−1, respectively. The ICA was successfully applied to detect 2,4-D in bean sprouts and cabbage samples and achieved good recoveries ranging from 94.7% to 104.3% with a coefficient of variation (CV) less than 8.3%. Hence, the ICA provides a sensitive, efficient and reliable detection method, which has broad application prospects in the detection of a large number of samples. [ABSTRACT FROM AUTHOR]