Development and Validation of an Immunoassay for the Determination of Tebuconazole Residues in Cereal Crops

Colourimetric Detection of Tebuconazole in Aqueous Solution Based on an Unmodified Aptamer and the Aggregation of Gold Nanoparticles

This paper illustrates the establishment of a colourimetric method for detection of the fungicide tebuconazole (TEB) in aqueous samples based on an unmodified TEB-specific aptamer and gold nanoparticles (AuNPs). In the absence of TEB, the AuNPs are coated with a TEB-specific aptamer and then stably dispersed a NaCl solution of high concentration, leading to a red solution and producing a maximum UV absorption peak at 520 nm. In the presence of TEB, due to the specific high affinity between TEB and the TEB-specific aptamer, the aptamer combines with TEB to form stable compounds, causing the AuNPs to be exposed in the solution and aggregate. The aggregated AuNPs turn the solution from red to blue, presenting a maximum UV absorption peak at 650 nm. Therefore, the concentration of TEB in the system can be quantitatively detected through the changes in absorbance. This TEB selective colourimetric biosensor detects TEB over a linear concentration range of 20 to 400 nM (R = 0.99385) and has a limit of detection (LOD) of 4.13 nM. The average recovery of TEB is 94.9–104.8 % in the application of actual water samples with the relative standard deviations (RSD) ranging from 1.01 to 5.34 %. With considerable sensitivity and selectivity, this aptasensor indicates great potential for TEB detection in aqueous samples.

Highly Specific Monoclonal Antibody and Sensitive Quantum Dot Beads-Based Fluorescence Immunochromatographic Test Strip for Tebuconazole Assay in Agricultural Products

A monoclonal antibody (mAb) was raised against tebuconazole (TEB) using a hapten where the p-chloro substituent of the TEB molecule was replaced with a long-chain carboxylic acid. The resulting mAb showed high sensitivity and specificity against TEB characterized by ELISA with a half-maximal inhibitory concentration (IC50) of 0.19 ng mL-1 and with cross-reactivity (CR) values below 0.01% to several analogues of triazole fungicides. On the basis of the mAb produced, a quantum dot beads-based fluorescence immunochromatographic test strip assay (QBs-FITSA) was developed for rapid and sensitive detection of TEB in agricultural product samples. The QBs-FITSA exhibited a linear detection range from 0.02 to 1.25 ng mL-1 with a limit of detection (LOD) of 0.02 ng mL-1. Furthermore, using produced mAb, multiple high-throughput rapid immunoassay formats could be achieved as a convenient monitoring tool for evaluation of human and environmental exposure to TEB.

Development of monoclonal immunoassays for the determination of triazole fungicides in fruit juices

Enzyme-linked immunosorbent assays (ELISAs) based on monoclonal antibodies for the detection of triazole fungicides have been developed. With this aim, hapten-protein conjugates, containing the common triazole and chlorinated aromatic moieties, were prepared. From mice immunized with these conjugates, several monoclonal antibodies (MAbs) with the ability to sensitively bind several triazoles with different specificity were obtained. Both analyte- and class-specific ELISAs were developed. The hexaconazole-specific immunoassay can determine this fungicide with a limit of detection of 0.3 mug/L in standard buffer. The so-called triazole-specific immunoassay allowed for the detection of tetraconazole, penconazole, cyproconazole, and myclobutanil, with limits of detection in the 0.1-0.7 mug/L range. These immunoassays were applied to the determination of triazoles in spiked fruit juices. Samples were adequately diluted to minimize the matrix effects. Coefficients of variation were below 30%, and recoveries ranged from 62 to 135%. Therefore, the developed immunoassays can determine triazole fungicides in fruit juices down to the maximum residue limits currently legislated, without any sample treatment other than dilution.

Identification of grouper (Epinephelus guaza), wreck fish (Polyprion americanus), and Nile perch (Lates niloticus) fillets by polyclonal antibody-based enzyme-linked immunosorbent assay

An indirect enzyme-linked immunosorbent assay (ELISA) has been developed for the species identification of grouper (Epinephelus guaza), wreck fish (Polyprion americanus), and Nile perch (Lates niloticus) fillets. The assay was performed in two different formats, microtiter plates and immunostick tubes, and uses polyclonal antibodies raised in rabbits against muscle-soluble proteins of grouper (anti-GSP), wreck fish (anti-WSP), and Nile perch (anti-PSP). The antibodies were made species-specific by blocking them with the heterologous soluble muscle proteins. Immunorecognition of polyclonal antibodies adsorbed to their specific fish samples was made with swine antirabbit immunoglobulins conjugated to the enzyme horseradish peroxidase. Subsequent enzymatic conversion of the substrate allowed unequivocal identification of the species studied.