Yirong Guo

Gold immunochromatographic assay for simultaneous detection of carbofuran and triazophos in water samples

Using a simple test for rapid identification and quantification of pesticide multiresidues in food and environmental samples is a long-cherished approach for practical monitoring purposes. Here two gold-based lateral-flow strips (strip A and strip B) were investigated for simultaneous detection of carbofuran and triazophos. For the strip A format, a bispecific monoclonal antibody (BsMcAb) against both carbofuran and triazophos was employed to prepare the immunogold probe. For the strip B format, anti-carbofuran monoclonal antibody (McAb) and anti-triazophos McAb separately labeled with colloidal gold were combined as detector reagents. By comparison of visual results from pesticide standard tests between the two formats, the strip B assay manifested higher sensitivities for both pesticides. Analysis of spiked water samples by the preferable strip indicated that the detection limits for carbofuran and triazophos were 32 and 4 microg/L, respectively. The strength of the portable one-step strip assay was in the simultaneous screening for two pesticides within a short time (8-10 min) without any equipment.

Development of a one-step strip for the detection of triazophos residues in environmental samples

Environmental and food safety issues now are recognized internationally, and pesticide residues play key roles as environment and food pollutants. It is crucial to develop methods for rapid determination of pesticide residues in environments and foods. A one-step strip based on nanocolloidal-gold-labeled monoclonal antibodies for detection of triazophos residue was developed. The nanocolloidal gold, with an average particle diameter of 25 nm (G25), was labeled to an antitriazophos monoclonal antibody. This conjugate was dispensed on the conjugate pad of a porous glass fiber. Ovalbumin hapten and goat anti-mouse IgG were dispensed on the nitrocellulose membrane and served as the test line (T-line) and control line (C-line), respectively. After conditions optimization, the one-step strip was finally developed for the residue determination of triazophos. The limit of detection (LOD) of the strip was 4 ng/mL for standard. The detection was not affected by the pH of the liquid sample but low total ion concentration will induce illegible C-line and T-line. The LOD for spiked samples of soil and water was 5ng/mL, with run time of no more than 10min.

Development of a Mab-based heterologous immunoassay for the broad-selective determination of organophosphorus pesticides.

A broad-selective monoclonal antibody (Mab) for organophosphorus (OP) pesticides was raised using heterologous indirect enzyme-linked immunosorbent assay (ELISA) to screen hybridomas. On the basis of this Mab, five coating antigens were used to develop homologous and heterologous indirect competitive ELISAs. With the most suitable competitor, a sensitive and broad-selective ELISA was developed. The IC(50) values were estimated to be 20.32 ng/mL for parathion, 21.44 ng/mL for methyl-parathion, 42.15 ng/mL for fenitrothion, and 58.85 ng/mL for isocarbophos. Spike recoveries were between 70.52 and 103.27% for the detection of single pesticide residues of the four OP pesticides in purple-clayed paddy soil. Moreover, the chosen ELISA was then applied to the detection of mixtures of parathion and methyl-parathion in soil samples. The average recovery and coefficient of variation were 80.91 and 4.82%, respectively. Results proved that this broad-selective ELISA would be useful for the multiresidue determination of OP pesticides.

Development of a Bispecific Monoclonal Antibody to Pesticide Carbofuran and Triazophos Using Hybrid Hybridomas

A mouse hybrid hybridoma (tetradoma) was derived from fusing hybridomas producing monoclonal antibody to N-methylcarbamate pesticide carbofuran with hybridomas producing monoclonal antibody to organophosphorus pesticide Triazophos. The prepared tetradoma line (12C1 to 2H12) secreted hybrid immunoglobulin exhibiting parental and bispecific binding characteristics. The effect of relevant physicochemical factors on the immunoassay based on the 12C1 to 2H12 bispecific monoclonal antibody had been studied to optimize the ELISA performance. The developed immunoassay showed that the detection limit (I(20)) were 0.36 and 1.89 ng/mL for triazophos and carbofuran, respectively, without obvious cross-reactivity to other related compounds. Water samples spiked with triazophos at 0.5, 1, and 5 ng/mL or carbofuran at 5, 10, and 20 ng/mL were directly analyzed by the developed ELISA format. The mean recovery of triazophos and carbofuran were 108.1% and 107.5%, with variation coefficient of 15.9% and 17.7%, respectively.

Residues determination of carbofuran in vegetables based on sensitive time-resolved fluorescence immunoassay

Abstract Using direct competitive time-resolved fluorescence immunoassay (TRFIA), a rapid, highly selective and sensitive method was developed for the determination of carbofuran residues in lettuce and carrot. The method was based on a direct competitive immunoassay using europium-labelled anti-carbofuran monoclonal antibody and carbofuran-ovalbumin as coated antigen. The sensitivity, estimated as the I 50 value, was 34.54 ng/mL, with a detection limit (I 10) of 1.94 ng/mL and a practical working range between 1.33 and 341.6 ng/mL. The average recoveries of carbofuran from lettuce and carrot were 81.26–108.0% and 113.9–124.8%, respectively. Eventually, confirmation test between TRFIA and enzyme-linked immunoassay (ELISA) was performed. It confirmed that the results given by the TRFIA method were in agreement with those of the ELISA method.

A sensitive chemiluminescent enzyme immunoassay for carbofuran residue in vegetable, fruit and environmental samples

Using the direct competitive chemiluminescent enzyme immunoassay (CLEIA), a rapid, highly selective and sensitive method for carbofuran determination was developed. Several physicochemical parameters such as chemiluminescent sensitiser, assay buffer, blocking substance and working concentration were optimised. Under the optimum conditions, the CLEIA method for carbofuran determination was generated successfully. The detection sensitivity of the IC50 value was 4.2 ng/mL at a practical working concentration ranging from 0.4 to 50 ng/mL, and the limit of detection (LOD) for carbofuran was 0.5 ng/mL. Recoveries of carbofuran spiked into vegetable, fruit and environmental samples were determined by CLEIA after sample matrix effect testing. Finally, the confirmation test between CLEIA and LC-MS/MS was finished. The results showed that CLEIA method had higher sensitivity than enzyme-linked immunosorbent assay method, and the LOD of a variety of samples reached the carbofurans maximum residue limit value laid down by Codex Alimentarius Commission.

An Improved Rapid On-Site Immunoassay for Triazophos in Environmental Samples

The suitability of enzyme-linked immunosorbent assay for rapid and on-site determination of triazophos in environmental samples was investigated. The optimized rapid ELISA can be completed in around 10 min at ambient temperature. A rapid sample preparation procedure was developed which can be performed on field site for fresh water and soil samples. The rapid assays can process 40 samples within 1 h including the sample preparation time. It can be concluded that this rapid assay would be a potential, effective method for monitoring triazophos in the environment, especially when quick Judgment regarding low or high contamination is critical.

Quantum-Dot-Based Lateral Flow Immunoassay for Detection of Neonicotinoid Residues in Tea Leaves

Neonicotinoid insecticides are commonly used for pest control on tea plantations as a result of their broad-spectrum activity. However, neonicotinoid residues released from tea leaves into tea infusions pose a dietary risk to consumers. Therefore, a rapid, sensitive, and reliable on-site detection method for neonicotinoids is needed. We developed a quantum-dot-based fluorescent lateral flow immunochromatographic strip (LFICS) combined with a broad-specific antibody for detection of typical neonicotinoids (imidacloprid, imidaclothiz, and clothianidin), with sensitivities [50% inhibitory concentration (IC50)] of 0.104-0.33 ng/mL and visual detection limits of 0.5-1 ng/mL. The strip assay could be completed in less than 30 min. Using the LFICS to analyze spiked tea samples (green tea, black tea, and oolong tea), the average recovery of the three neonicotinoids ranged between 71 and 111%, with the coefficient of variation below 12%. The results from the LFICS tests for field samples were consistent with results from ultraperformance liquid chromatography-tandem mass spectrometry. The newly developed strip is a useful tool for the on-site detection of neonicotinoid residues in tea.