VHH-ELISA kit for one-step detection of fipronil residues and application thereof
A kit, fipronil technology, applied in the field of genetic engineering and ELISA detection, can solve the problems of complex pretreatment, high cost, poor specificity, etc.
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Embodiment 1
[0028] Example 1 Preparation of fipronil-coated antigen
[0029] A conjugated complex was prepared with hapten and bovine serum albumin as the coating antigen. The preparation method is as follows:
[0030](1) Dissolve 8.8mg of fipronil-6C (MW=440.15, 0.02mmol), 2.65mg of NHS (MW=115, 0.024mmol), 4.8mg of DCC (MW=206, 0.023mmol) in 200μL of anhydrous DMF , stirred overnight at room temperature. Centrifuge the reaction solution (5000rpm, 10min), discard the precipitate, and the supernatant is the active ester.
[0031] (2) Dissolve 20mg of BSA (MW=67000) in 2mL of carbonate buffer solution (0.05mol / mL, pH 9.5), add 150μL of active ester solution drop by drop under stirring, slowly add in about 20-30min Finish. Then the stirring reaction was continued at room temperature for 4-6 h.
[0032] (3) The reaction solution was put into a dialysis bag and dialyzed with PBS (0.01 mol / L, pH7.4). The liquid was changed every 6-8 hours, and the liquid was changed 5-6 times in total. ...
Embodiment 2
[0033] Example 2 Construction of anti-fipronil VHH-AP genetically engineered antibody
[0034] Firstly, the specific fipronil VHH gene fragment, ie nanobody (SEQID NO: 1), was screened by phage display technology.
[0035] Then the specific fipronil nanobody plasmid was extracted, and the VHH gene fragment was amplified by PCR.
[0036] Wherein the PCR reaction system is as follows:
[0037]
[0038] The reaction procedure is as follows:
[0039]
[0040] The PCR primer sequences are as follows (SEQ ID NO:2-3):
[0041] AP-F:
[0042] 5'-CATGCCATGACTGTGGCCCAGCCGGCCCAGKTGCAGCTCGTGGAGTCNGGNGG-3'
[0043] AP-R5:
[0044] 5'-CATGCCATGACTCGCGGCCCCCGAGGCCTGCTTGCATACTTCATTCGTTCCTG-3'
[0045] Wherein, K represents the base G / T, and N represents the base A / T / G / C.
[0046] Then modify the VHH gene with restriction enzyme SfiI to obtain sticky ends, and then connect the VHH gene fragment to the vector Pecan 45 by T4 ligase. The vector Pecan 45 contains the AP (alkaline phos...
Embodiment 3
[0048] Example 3 Expression of anti-fipronil VHH-AP genetically engineered antibody
[0049] The positive monoclonal VHH-AP plasmid was extracted, transformed into Escherichia coli TOP10F' competent cells, and spread on solid medium for overnight culture after recovery. The next day, a single clone was picked and cultured in SB-carboxybenzyl medium, and IPTG (isopropylthiogalactopyranoside) was added to induce overnight expression. The next day, the cells were lysed with an ultrasonic breaker, filtered with a filter membrane and purified with a nickel column, that is, the VHH-AP plasmid was separated and purified by affinity chromatography using the histidine tag and nickel chloride in the nickel column to obtain high-purity fluorine Chlornil genetically engineered antibody. After amino acid sequencing analysis, the amino acid sequence of the obtained anti-fipronil VHH-AP genetically engineered antibody is shown in SEQ ID NO:4.
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