A lateral flow immunoassay method for the rapid detection of acetochlor and alachlor in vegetable oil by sensitivity enhancement by using dimethyl-ß-cyclodextrin.

Acetochlor is an endocrine disruptor. The acetochlor residue is strongly lipophilic and can be enriched into products during the manufacturing process. In this study, we found that dimethyl-ß-cyclodextrin (DM-ß-CD) solution could decrease the apparent oil/water partition coefficient (Koil-w) of acetochlor and increase the sensitivity of fluorescence lateral flow immunoassay (LFIA) for acetochlor simultaneously. Based on this, a simple LFIA method for the determination of acetochlor and alachlor residues in vegetable oil was established. The detection process only involves vortex mixing of an oil sample and dimethyl-ß-cyclodextrin solution in a 1 : 3 (V/V) ratio, loading the water phase onto the immunoassay strips and reading the results. Under optimized conditions, the LOD for acetochlor in oil was 3.53 ng g-1, and the working range was 12.03-2000.00 ng g-1. The recoveries of spiked samples ranged from 91.69% ± 1.12% to 112.23% ± 2.20%. Meanwhile, the cross reactivity for alachlor was 108.22%, while for other investigated acetochlor analogues it was less than 1%, and the recoveries of alachlor were from 92.90% ± 8.03% to 113.53% ± 3.40%, which indicate that this method can detect acetochlor and alachlor simultaneously. Compared with the traditional detection method, the pre-treatment process of the proposed method is "green" and simple, and can be applied to the on-site rapid detection of acetochlor and alachlor in vegetable oil and can provide inspiration for the detection of other lipophilic pollutants.

Comparison of lateral flow immunoassays based on oriented and nonoriented immobilization of antibodies for the detection of aflatoxin B1.

In recent years, some studies have found that oriented immobilization of antibodies to microspheres can fully expose the antigen binding sites of antibodies, which can improve the sensitivity of sandwich immunoassays for the detection of proteins. Can this antibody immobilization strategy also improve the sensitivity of competitive immunoassays for the detection of small molecules? To answer this question, the conjugate MS-SPG-Ab (oriented immobilization of aflatoxin B1 antibody to time-resolved fluorescent microspheres via streptococcal protein G) and the conjugate MS-Ab (nonoriented immobilization of aflatoxin B1 antibody to time-resolved fluorescent microspheres) were prepared, and a lateral flow immunoassay (LFIA) for the detection of aflatoxin B1 (AFB1) was established. The detection performance of the two methods was compared. The results showed that under the condition that the number of "effective" antibodies immobilized on TRF-MS was similar, compared with the nonoriented immobilization strategy (IC50 = 0.21 ng mL-1), the LFIA method established by the oriented immobilization strategy reduced the sensitivity of AFB1 detection (IC50 = 0.37 ng mL-1). However, this method can obtain higher detection precision for AFB1, the CV values were all below 8%. And it has stronger tolerance to the matrix of maize and peanut samples. The bias of LFIAs based on oriented immobilization technology (-14.93%-7.92%) was lower than nonoriented immobilization technology (28.16%-34.19%) for AFB1 detection in the two sample extracts. This study suggests that the LFIA method based on the oriented immobilization of antibodies can improve the accuracy of the detection results when performing rapid screening of small molecules.

A time-resolved fluorescence lateral flow immunochromatographic assay based on oriented immobilized antibodies for the ultrasensitive detection of C-peptides in human serum.

C-peptide is a biomarker that has clinical implications for the diagnosis of a variety of diseases. In this study, an ultrasensitive time-resolved fluorescence lateral flow immunochromatographic assay (TRF-LFIA) method was established for the detection of C-peptides in human serum. The key to this method is the oriented immobilization of antibodies anti C-peptide on TRF microspheres that can sufficiently expose the antigen binding site. The limit of detection (LOD) of this method for C-peptide was 0.005 ng mL-1, which is 10-fold less than that of TRF-LFIA method based on nonoriented immobilizing antibodies. The working range of this method was 0.005-250 ng mL-1, and the spiked recoveries of C-peptide in human serum were 106.85%-116.40% with a CV value less than 10%. The test results of actual serum samples had good consistency (R2 > 0.97) with the Roche Cobas 8000 automatic chemiluminescence immunoassay analyzer. This method can be utilized for the point-of-care testing (POCT) of C-peptide, and the oriented immobilizing method can also be used to construct highly sensitive probes to improve the sensitivity of other analytes in the POCT platform.

Development of a quantum dot-based lateral flow immunoassay with high reaction consistency to total aflatoxins in botanical materials.

Total aflatoxins (AFTs) are an important safety indicator for botanical materials, but at present, rapid detection technology for AFTs is seldom reported. In this study, the monoclonal antibody with similar reactivity to total aflatoxins was produced, and the quantum dot-based lateral flow immunoassay (QD-LFIA) coupled with a portable device was developed to rapidly determine AFT residues in botanical materials. The half maximal inhibitory concentrations (IC50) of the QD-LFIA for AFB1, AFB2, AFG1, AFG2, AFM1, and AFM2 were 10.57, 12.64, 11.34, 12.67, 10.13, and 12.75 µg kg-1, respectively, which show high reaction consistency to total aflatoxins. For different botanical materials, the sample was simply extracted with methanol-water and diluted with PBS, and the sample solution was directly loaded onto the QD-LFIA strip for determination. To overcome interference from the matrix effects, specific standard curves were established for each kind of botanical material. The detection limit of AFTs in 6 different botanical materials was 0.95~2.03 µg kg-1 with a linear range of 2~120 µg kg-1. The spiked recoveries of AFTs in botanical materials of different species and localities of growth were 75~105% with a coefficient of variation below 15%. The test results of the actual samples are consistent with the Chinese national standard test method. This study provides an easy-to-use method to rapidly determine AFTs in different botanical materials. Graphical abstract.

A mix-and-detect method based on colloidal gold immunochromatographic assay for on-site detection of zearalenone in edible oils.

The common methods to detect zearalenone (ZEN) in edible oils need organic solvents to extract ZEN and then some sample purification process before detection, so, it is not convenient for on-site use. Here a simple method without organic solvents and a sample purification process was developed for the determination of ZEN in edible oils. The detection process only needs mixing oil with a surfactant solution in the indicated ratio and then loading the mixture onto a colloidal gold immunochromatographic (CGI) strip for detection. The optimized surfactant was AEO15 among the seven surfactants studied in this paper. The ZEN residue in edible oil could be quantitatively determined with a detection limit of 44.3 ng g-1, and the working range of the standard curve was from 50 to 800 ng g-1. This method has been successfully applied to the detection of ZEN in plant oils with recoveries ranging from 81 ± 7% to 129 ± 9% for spiked samples. The detection results for the ZEN residue in oil samples from a local market by this method were in good agreement with those obtained by the national standard method.