1. Research background
Food safety is a livelihood project that requires special attention. At present, food safety issues in my country are still dominated by pesticide and veterinary drug residues, pathogenic bacteria, and illegal additives. Among them, pesticide residues have attracted much attention due to their extensiveness and diversity. There are more than 1,500 types of pesticides (active ingredients) developed around the world. According to their chemical composition, they can be divided into organophosphorus, organochlorine, pyrethroid, carbamate, phenoxyacetic acid, organotin, etc. The improper use of pesticides and other reasons often cause pesticide residues to exceed the standard, and pesticide residues are harmful to human health, causing acute or chronic poisoning, reducing human immunity, causing cancer, teratogenesis, and mutagenesis, and even causing individual deaths. Affecting the foreign trade of agricultural products will also cause serious pollution to the environment.
At present, the detection of pesticide residues is mainly divided into the following categories:(1) Instrumental analysis methods, including liquid chromatography, gas chromatography, etc. These methods are highly precise, but the instruments are expensive; (2) Immunoassay methods , Including enzyme-linked immunosorbent assay (ELISA), colloidal gold immunochromatography, etc. The ELISA method has high detection throughput, but requires multiple steps of operation and washing. The colloidal gold immunochromatography method is simple and easy to operate, but the sensitivity is insufficient. None of these methods can satisfy the rapid and sensitive detection of trace pesticide residues in food. Therefore, it is urgent to establish a fast, sensitive and simple pesticide residue detection method to ensure food safety.
Based on this requirement, Professor Chen Yiping’s research group combined the enzyme inhibitory properties of acetamiprid pesticides with a paramagnetic ion conversion system to construct a one-step hybrid dual-enzyme-mediated Fe2+/Fe3+ magnetic relaxation sensor. It is used for the rapid and highly sensitive detection of acetamiprid in fruit and vegetable samples.
2. Related research work:Construction of a dual-enzyme-mediated Fe2+/Fe3+ magnetic relaxation sensor and its application in pesticide detection
(1) Research method
In this work, a dual-enzyme-mediated Fe2+/Fe3+ magnetic relaxation sensor system was constructed based on the enzyme inhibitory properties of the pesticide Acetamiprid. Acetylcholinesterase (AChE) substrate acetylcholine chloride (ACh) produces choline, which is then catalyzed by choline oxidase (CHO) to produce hydrogen peroxide, and hydrogen peroxide can induce the conversion of Fe2+/Fe3+, which in turn causes horizontal Changes in relaxation time (T2). In this method, acetamiprid can inhibit the activity of acetylcholinesterase (AChE), cut off the catalytic reaction, thereby reducing the production of choline and hydrogen peroxide. The reduction of hydrogen peroxide will reduce the conversion degree of Fe2+/Fe3+, thereby affecting the magnetic signal. Therefore, the correlation between the magnetic signal and acetamiprid can be established (Figure 1). The sensor has the advantages of fast, stable, sensitive, etc., which can be attributed to two factors:(1) Fe2+/Fe3+ in the aqueous solution is uniform and stable, and the signal output is stable and sensitive; (2) The cascade of Fe2+/Fe3+ conversion mediated by dual enzymes The reaction only requires”one-step mixing”, which improves the detection efficiency and sensitivity.
(2) Experimental results
This work first verified the feasibility of the Fe2+/Fe3+ valence state conversion and the dual-enzyme-mediated H2O2 generation system through hydrogen peroxide test strips, potassium permanganate redox color development and UV spectrum scanning (Figure 2) . On this basis, a magnetic relaxation biosensor based on Fe2+/Fe3+ valence state conversion was constructed, and the concentration of acetylcholine chloride, acetylcholinesterase and Fe2+ was optimized (Figure 3). In this work, acetamiprid was further detected and compared with the spectrophotometric method and the traditional enzyme inhibition method. The experimental results show that the sensitivity of Fe2+-T2 magnetic relaxation sensor to detect acetamiprid is 180 times that of spectrophotometric method and 335 times that of traditional enzyme inhibition method (Figure 4). Therefore, the sensor has good analytical performance and application potential in pesticide residue detection.
(3) Paper related information:
This work was published in Journal of Hazardous Materials (Journal of Hazardous Materials, 2021, 403, 123619, IF=9.0).
Funding information for the paper:Supported by the National Natural Science Foundation of China (81671784, 31801638) and the Central University Fundamental Research Fund (2662019PY005).
Link to the paper:https://doi.org/10.1016/j.jhazmat.2020.123619