Design and Characterization of a Novel Hapten and Preparation of Monoclonal Antibody for Detecting Atrazine

A novel sustainable immunoassay for sensitive detection of atrazine based on the anti-idiotypic nanobody and recombinant full-length antibody

Immunoassays have been widely used to determine small-molecule compounds in food and the environment, meeting the challenge of obtaining false positive or negative results because of the variance in the batches of antibodies and antigens. To resolve this problem, atrazine (ATR) was used as a target, and anti-idiotypic nanobodies for ATR (AI-Nbs) and a recombinant full-length antibody against ATR (ATR-rAb) were prepared for the development of a sustainable enzyme-linked immunosorbent assay (ELISA). AI-Nb-7, AI-Nb-58, and AI-Nb-66 were selected from an immune phage display library. ATR-rAb was produced in mammalian HEK293 (F) cells. Among the four detection methods explored, the assay using AI-Nb-66 as a coating antigen and ATR-rAb as a detection reagent yielded a half maximal inhibitory concentration (IC50) of 1.66 ng mL-1 for ATR and a linear range of 0.35-8.73 ng mL-1. The cross-reactivity of the assay to ametryn was 64.24%, whereas that to terbutylazine was 38.20%. Surface plasmon resonance (SPR) analysis illustrated that these cross-reactive triazine compounds can bind to ATR-rAb to varying degrees at high concentrations; however, the binding/dissociation kinetic curves and the response values at the same concentration are different, which results in differences in cross-reactivity. Homology modeling and molecular docking revealed that the triazine ring is vital in recognizing triazine compounds. The proposed immunoassay exhibited acceptable recoveries of 84.40-105.36% for detecting fruit, vegetables, and black tea. In conclusion, this study highlights a new strategy for developing sustainable immunoassays for detecting trace pesticide contaminants.

Generating Monoclonal Antibodies against Buprofezin and Developing Immunoassays for Its Residue Detection in Tea Samples

The synthesis of a hapten and antigen for the preparation of a monoclonal antibody (mAb) for buprofezin is described. The recognition mechanism of hapten and buprofezin by monoclonal antibodies (mAb-19F2) is described. The effectiveness of the mAb-19F2 immunoassay technique was assessed, and the effective detection of buprofezin in tea samples was achieved through the establishment of indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and colloidal gold immunochromatography assay (GICA). The mAb-19F2 subtype was IgG1, with an IC50 of 1.8 ng/mL and a linear range (IC20-IC80) of 0.6-5.4 μg/L, and had a cross-reaction rate of less than 0.18% with 29 other pesticides (neonicotinoids and insect growth regulators). The study identified π-π stacking interactions between hapten and TYR-61 at the mAb-19F2 site and alkyl/phosphate interactions with TRP-105 and ARG-103. The ic-ELISA had an IC50 of 12.9 ng/mL in green tea and 5.65 ng/mL in black tea, with a recovery rate of 92.4%-101.0% and RSD of 2.1%-4.8%. The GICA had a limit of detection (LOD) was 500 ng/mL, with the complete disappearance of the test lines visible to the naked eye. The limit of quantitation (LOQ, IC20) was determined to be 16.8 ng/mL. Additionally, the developed GICA showed no cross-reactivity with neonicotinoid pesticides. The recovery rate of tea spiked recovered samples was 83.6%-92.2%, with an RSD of 5.3%-12.6%, and the results were consistent with the LC/MS method. This study is important for the real-time detection of buprofezin residues to ensure food safety and human health.

Application of Immunoassay Technology in Food Inspection

Food safety is as important as ever, and the safeguards implemented to inspect and reduce pesticides, veterinary drugs, toxins, pathogens, illegal additives, and other deleterious contaminants in our food supply has helped improve human health and increase the length and quality of our lives [...].

Isolation of atrazine nanobodies enhanced by depletion of anti-carrier protein phages and performance comparison between the nanobody and monoclonal antibody derived from the same immunogen

Nanobody, a single domain antibody, has been shown a great promise for immunoassay (IA) applications. To improve the panning efficiency so as to obtain a valuable nanobody, anti-carrier protein phages in a phage display library were depleted to enhance the selection of nanobodies against the herbicide atrazine by using immunomagnetic beads conjugated with bovine serum albumin (IMB-BSA). The depletion of anti-carrier protein phages from the atrazine phage display library tripled the number of atrazine positive phage clones after four rounds of panning. One of the most sensitive phage clones Nb3 selected from the IMB-BSA depleted library was used to compare the performance with the monoclonal antibody (mAb 5D9) developed from the same immunogen. The Nb3-based IA exhibited similar specificity with the mAb 5D9-based IA, but greater thermostability and organic solvent tolerance. The half-maximum inhibition concentration (IC₅₀) of the former was 3.5-fold greater than that of the latter (36.7 ng/mL versus 10.2 ng/mL). Because the Nb3-based IA was more robust than the mAb 5D9-based IA, the method detection limit of the two assays was 7.8 ng/mL of atrazine in river samples. The depletion strategy can increase the chance to acquire high quality nanobody and can be applicable for effective development of nanobodies against other small molecules.

Production of a Monoclonal Antibody for the Detection of Forchlorfenuron: Application in an Indirect Enzyme-Linked Immunosorbent Assay and Immunochromatographic Strip

In this study, a monoclonal antibody (mAb) specific to forchlorfenuron (CPPU) with high sensitivity and specificity was produced and designated (9G9). To detect CPPU in cucumber samples, an indirect enzyme-linked immunosorbent assay (ic-ELISA) and a colloidal gold nanobead immunochromatographic test strip (CGN-ICTS) were established using 9G9. The half-maximal inhibitory concentration (IC₅₀) and the LOD for the developed ic-ELISA were determined to be 0.19 ng/mL and 0.04 ng/mL in the sample dilution buffer, respectively. The results indicate that the sensitivity of the antibodies prepared in this study (9G9 mAb) was higher than those reported in the previous literature. On the other hand, in order to achieve rapid and accurate detection of CPPU, CGN-ICTS is indispensable. The IC₅₀ and the LOD for the CGN-ICTS were determined to be 27 ng/mL and 6.1 ng/mL. The average recoveries of the CGN-ICTS ranged from 68 to 82%. The CGN-ICTS and ic-ELISA quantitative results were all confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) with 84-92% recoveries, which indicated the methods developed herein are appropriate for detecting CPPU in cucumber. The CGN-ICTS method is capable of both qualitative and semiquantitative analysis of CPPU, which makes it a suitable alternative complex instrument method for on-site detection of CPPU in cucumber samples since it does not require specialized equipment.

Obtaining a Monoclonal Antibody against a Novel Prometryn-Like Hapten and Characterization of Its Selectivity for Triazine Herbicides

In this study, a previously unreported 3-((4-(isopropylamino)-6-(methylthio)-1,3,5-triazin-2-yl) amino) butyric acid hapten was designed and synthesized. This maximized the exposure of the antigen-determinant isopropyl of prometryn to the immune system in animals to induce the production of anticipated highly specific anti-prometryn antibodies. The hapten has a molecular weight of 285.37 Da. The compound was confirmed by nuclear magnetic resonance hydrogen spectroscopy (¹H NMR), nuclear magnetic resonance carbon spectroscopy (¹³C NMR), and high-resolution mass spectrometry (HRMS). By using the active ester approach, immunogens and coated antigens were created. Bovine serum albumin (BSA) was used as an immunogen, along with the successfully produced hapten, to immunize mice. The IC₅₀ value of mouse monoclonal anti-prometryn antibody (mAb) 7D4 (the quantity of analyte that generated 50% prometryn inhibition) was 3.9 ng/mL. The anti-prometryn mAb was of the IgG1 subclass. The IC₂₀ (80% binding level (B/B₀) of prometryn)-IC₈₀ (20% binding level (B/B₀) of prometryn) range of the anti-prometryn monoclonal antibody standard curve working range was 0.9-18.1 ng/mL. The prepared mAb has good characteristics because it can specifically recognize prometryn, and the cross-reaction rates for ametryn, desmetryn, and terbumeton were 34.77%, 18.09%, and 7.64%, respectively. The cross-reaction rate with the other seven triazines was less than 1%. The hapten structure proposed can serve as an additional tool for modulating selectivity in detecting triazines.