China is a big country in agriculture. In order to ensure the bumper harvest of agriculture, the use of pesticides is essential. The pesticides commonly used in China are the most widely used pesticides, and their toxicity is also greater than other pesticides. Commonly used insecticides mainly include organic chlorine pesticides, organic phosphorus insecticides, carbamate insecticides, pyrethroid insecticides, and the like. However, while ensuring the increase of agricultural production, the use of pesticides will also cause certain pesticide residue contamination.
Pesticide residue refers to the general term for residues of pesticides, toxic metabolites, degradants, and impurities that remain in organisms, foods, and the environment after pesticides are used. Pesticide residues have certain toxins that will directly or indirectly endanger people's health.
With the development of the economy and the improvement of people’s living standards, people have higher requirements for food hygiene and safety. The problem of pesticide residue contamination has become one of the important issues related to food safety. The rapid detection of pesticide residues has attracted widespread attention.
At present, commonly used pesticide residue detection methods include gas chromatography (GC), thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and so on. However, most of these methods require the pretreatment of the sample to be analyzed, and the operation is complicated, and it cannot meet the requirement of on-site rapid detection of the sample.
Biosensors are widely used in various fields such as biology, chemistry, physics, and information. They have high selectivity, high accuracy, quick analysis, and simple operation. They are an advanced detection and monitoring method and were applied as early as the 1950s. For the detection of pesticide residues. At present, it is widely used in food industry, fermentation process, environmental monitoring, medical diagnosis and other fields.
1 Biosensors 1.1 Composition and working principle of biosensors Biosensors refer to the use of immobilized biomolecule binding transducers to detect or respond to specific environmental chemicals in or out of the body. A device.
Biosensors are mainly composed of two parts: specific biomolecules and transducers. The biomolecules immobilized on the sensor have specific selectivity and can detect specific chemical substances in the body's internal and external environment, and interact with them to generate a response change signal; the transducer can biochemically and electrochemically react The resulting biochemical reaction signal is converted into an electrical signal, which is then subjected to amplification of the electrical signal and analog-to-digital conversion to measure the analyte and its concentration. The selectivity of the sensor determines the ability to identify specific biomolecules, and the sensitivity of the sensor depends on the transducer's ability to amplify the response signal.
1.2 Classification of Biosensors Biosensors can be classified into two types, affinity sensors and metabolic sensors, depending on the type of interaction between the sensor and the analyte; depending on the transducer used, the biosensor can be further classified as a biosensor. Electrode sensors, semiconductor sensors, thermal biosensors, optical biosensors, sonic biosensors, FET biosensors, etc. Generally, depending on the use of sensitive elements, ie, identification elements, biosensors can be roughly divided into enzyme sensors, immunosensors, and tissue/microbial sensors.
1.2.1 Enzyme Sensors An enzyme sensor, also known as an enzyme electrode, is generally composed of an immobilized enzyme membrane and an electrode. Enzymes on immobilized enzyme membranes can specifically identify the analytes, catalyze the corresponding reaction changes, and trigger electrical signals. Since the enzyme has a high degree of specificity for the substrate, the material detected by the enzyme electrode differs depending on the enzyme on the membrane, and the sensor constituting it is different. But the only downside is that the enzyme's price is higher and its stability is slightly worse.
1.2.2 Immunosensors Immunosensors consist of antibodies or antigens and transducers and are used primarily for the detection of antigens or antibodies. When antigens and antibodies are combined, they can cause changes in the charges or groups that they carry, which can lead to changes in the signals that can be detected by the transducers, and can achieve the purpose of detecting the analytes.
1.2.3 Tissue/Microbial Sensors The activity and stability of enzymes in plant and animal tissues are higher than the isolated enzymes, and the materials are easily available and the preparation is simple. If the tissue skin of animals and plants is directly used as a sensor to prepare a biosensor, it becomes a tissue sensor. If the living microorganism is directly fixed on the surface of the electrode to make a sensor, it will become a microbial sensor. Microorganisms are more commonly used by bacteria and yeasts. At the same time, such sensors can also use microbial life activities (such as respiration) to detect the concentration of some metabolites. The disadvantage is that stability and selectivity have yet to be improved.
1.2.4 Nano-sensors Nano-sensors with biological probes that selectively bind target molecules are called nano-biosensors. Nanotechnology is the study of the structure and properties of substances at the nanoscale, and utilizes the science and technology of making materials with nanosized single atoms and molecules. Nanoscale biomaterials have unique chemical and physical properties such as surface effects, small size effects, and macroscopic quantum tunneling effects. Applying nanomaterials to biosensors can greatly improve the sensitivity and accuracy of biosensors and make detection more efficient. The introduction of platinum nanoparticles into the glucose oxidase electrode can improve the performance of the enzyme electrode and increase the current response value of the electrode by two orders of magnitude.
Nanotechnology is mostly involved in biosensor biomarkers, signal amplification, enzyme immobilization, and interference elimination techniques in the form of nanoparticles, nanodevices, and nanostructures. At present, there are many reports on nanosensors in the research report on nanosensors.
1.3 Advantages of biosensors Biosensors integrate modern biotechnology and electronic technology. Compared with traditional methods, biosensors have the following advantages: less sample detection and no need for pretreatment, no need to add other reagents, and can simultaneously complete the sample Separation and detection of the tested components; response to shaanxi, can be used repeatedly, and can achieve continuous online monitoring; instrument cost is low, easy to popularize.
2 Application of Biosensors for Detection of Pesticide Residues There are many biosensors currently used for the detection of pesticide residues in domestic biosensors, including enzyme sensors and immunosensors.
2.1 Enzyme Sensor 2.1.1 Biosensor Based on Enzyme Inhibition Principle This biosensor is mainly based on the inhibitory effect on cholinesterase and detects organophosphorus and carbamate pesticides in fruits and vegetables, but the inhibition is mostly irreversible inhibition; regeneration difficult. At present, studies report more on acetylcholine esters.
Acetylcholinesterase is widely present in animal tissues and blood, insect tissues and plants. Its main function is to rapidly hydrolyze acetylcholine to choline and acetic acid, ensuring effective delivery of choline. Organophosphorus and carbamate pesticides can specifically bind to acetylcholinesterase, inhibiting the activity of the enzyme, thereby preventing the hydrolysis of acetylcholine. When the enzyme is inhibited, the magnitude of the oxidation current can accurately reflect the extent to which the enzyme is inhibited, thereby detecting the concentration of the pesticide residue. As early as the 1950s, acetylcholinesterase has been used to detect pesticide residues.
Zhang Xianzhen and other biosensors using immobilized acetylcholinesterase as a recognition element to detect trichlorfon, trichlorfon is an organophosphate insecticide. After research, it was found that the frequency of the sensor was linearly related to the concentration of trichlorfon. The detection limit of trichlorfon was reduced to 2 nglml, and the detection time was less than that of the chromatographic method. Zhao Penglin et al. used immobilized butyrylcholinesterase BChE (EC 3.1.1.8) as a recognition element and a spectrophotometer as a transducer to construct a flow injection type BChE enzyme biosensor containing citrate buffer. Under liquid conditions, there is a good linearity in the concentration range of carbaryl in the range of 0.2-50 ug/ml. Zhang Shuping uses an nitrocellulose membrane with a pore size of 0.45 grn as the immobilized carrier. The acetylcholinesterase sensor and the national standard method respectively detect pesticide residues in fruit and vegetable samples that have been sprayed with the same amount of pesticide, and spray 10.0 mg/L of urethane. Pesticides formylcarbazole and 10.0 mg/L organophosphorus pesticide methamidophos. The results of the biosensor assay were 6.56 mg, L and 7.27 mg/L, respectively, which was slightly lower than that of the GC method. However, the detection time was only 30 minutes, which was obviously more promising than the GC method. Wei Fuxiang, etc. using acetylcholinesterase biosensor technology, apple, cucumber as a sample, using standard addition method for analysis, determination of organophosphorus pesticide residues in fruits and vegetables. The detection limits of malathion and methyl parathion were 4.80×10-11 and 2.93×10-10 mol/L, respectively.
The enzymatic sensing based on the principle of enzyme inhibition can use the method of immobilizing two kinds of enzymes at the same time, so that the sensor can simultaneously detect the various pesticides.
2.1.2 Biosensors Based on Enzymatic Hydrolysis Principle The commonly used hydrolases on biosensors are organic phosphate hydrolase (OPH), acid phosphohydrolase (OPAA) and parathionine hydrolase (PH). Reported more is organophosphorous hydrolase.
Organic Phosphoric Hydrolase (OPH) can hydrolyze organophosphorus pesticides, producing protons, ethanol and other products. These products can provide signals that can be detected to the relevant devices, and the transducers can then convert these signals into quantifiable light or electrical signals to detect the concentration of organophosphorus pesticides. At present, there are few domestic reports on such sensors, and there are many foreign ones.
Walker et al. developed a polymeric colloidal crystal hydrogel optical sensor that can be used to detect the concentration of parathion in methyl. The reaction of organophosphorus hydrolase (OPH) with methyl parathion produces a certain amount of protons and induces changes in the lattice and stability of the hydrogel. The sensor measures the concentration of methyl parathion by detecting this change. The lower limit of detection of methyl parathion in this sensor can be reduced to 0.2 umol/L. Zourob et al. used a pH-sensitive polymer and an organophosphorous enzyme to construct a magnetoelectric sensor that can detect organophosphorus pesticides in hydrogels. The concentration of pesticide residues was determined by measuring the change in pH caused by the hydrolysis of organophosphorus pesticides catalyzed by organophosphorus hydrolase. The sensor can successfully lower the limit of detection of paraoxon and parathion to 1×10-7 and 8.5×10-7 mol/L.
2.2 Immunosensors Immunosensors are easy to operate, have fast effects, and have good sensitivity and specificity. It mainly uses pesticides and specific antibody binding reactions to detect pesticides, herbicides and other pesticide residues in food and vegetables.
Yang Mingyan et al. constructed a DDT immunosensor based on self-assembled DDT antibody immobilization technology and dual-channel SAW detection technology. Tests have shown that under the static injection test method, the sensor has a high degree of sensitivity and high repeatability. In the detection range of 6×10-9 ug/L to 29×10-9 ug/L, the output frequency of the sensor changes. The concentration of DDT is in a good linear relationship. The detection limit for DDT can be reduced by 551.57 × 10-9 μg/L, and the response time is 40 min. Michele et al. used an herbicide atrazine-derived protein to construct an immunosensor capable of detecting atrazine concentration based on reflectance-absorption infrared spectroscopy. The sensor indirectly induces changes in the infrared signal through changes in anti-atrazine antibodies and antigen binding on the sensor, thus detecting the atrazine content. The test confirmed that the amount of atrazine detected by the sensor was exactly the same as that measured by the enzyme-linked immunosorbent assay under the same conditions. The Disperse Wave all-fiber immunosensor constructed by Long et al. can quickly detect the concentration of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), and can reduce the detection line of 2,4-D by 550.07ug. /L. The sensor can be reused for 100 detection cycles and is easy to carry, making it possible for the immune sensor to quickly detect pesticide residues on site.
3 Outlook Compared with foreign countries, China's biosensor research is relatively backward, and mainly focused on individual types of sensors, such as enzyme sensors, immune sensors. At the same time, biosensors are in good condition in laboratory conditions, but if they are to be widely used in industrial production, their stability, accuracy, and repeatability are the biggest problems that still need to be further improved.
The combination of biosensors and nanotechnology and computers has laid a foundation for the further improvement of sensors. Biosensors will tend to be miniaturized, multi-functionalized, and intelligent. They will be easier for people to carry and use. In the short-term, they will coexist with traditional detection methods. With the maturation of performance, biosensors have great development potential and have broad prospects in the rapid detection of food residue and pesticide residues.
Pesticide residue refers to the general term for residues of pesticides, toxic metabolites, degradants, and impurities that remain in organisms, foods, and the environment after pesticides are used. Pesticide residues have certain toxins that will directly or indirectly endanger people's health.
With the development of the economy and the improvement of people’s living standards, people have higher requirements for food hygiene and safety. The problem of pesticide residue contamination has become one of the important issues related to food safety. The rapid detection of pesticide residues has attracted widespread attention.
At present, commonly used pesticide residue detection methods include gas chromatography (GC), thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and so on. However, most of these methods require the pretreatment of the sample to be analyzed, and the operation is complicated, and it cannot meet the requirement of on-site rapid detection of the sample.
Biosensors are widely used in various fields such as biology, chemistry, physics, and information. They have high selectivity, high accuracy, quick analysis, and simple operation. They are an advanced detection and monitoring method and were applied as early as the 1950s. For the detection of pesticide residues. At present, it is widely used in food industry, fermentation process, environmental monitoring, medical diagnosis and other fields.
1 Biosensors 1.1 Composition and working principle of biosensors Biosensors refer to the use of immobilized biomolecule binding transducers to detect or respond to specific environmental chemicals in or out of the body. A device.
Biosensors are mainly composed of two parts: specific biomolecules and transducers. The biomolecules immobilized on the sensor have specific selectivity and can detect specific chemical substances in the body's internal and external environment, and interact with them to generate a response change signal; the transducer can biochemically and electrochemically react The resulting biochemical reaction signal is converted into an electrical signal, which is then subjected to amplification of the electrical signal and analog-to-digital conversion to measure the analyte and its concentration. The selectivity of the sensor determines the ability to identify specific biomolecules, and the sensitivity of the sensor depends on the transducer's ability to amplify the response signal.
1.2 Classification of Biosensors Biosensors can be classified into two types, affinity sensors and metabolic sensors, depending on the type of interaction between the sensor and the analyte; depending on the transducer used, the biosensor can be further classified as a biosensor. Electrode sensors, semiconductor sensors, thermal biosensors, optical biosensors, sonic biosensors, FET biosensors, etc. Generally, depending on the use of sensitive elements, ie, identification elements, biosensors can be roughly divided into enzyme sensors, immunosensors, and tissue/microbial sensors.
1.2.1 Enzyme Sensors An enzyme sensor, also known as an enzyme electrode, is generally composed of an immobilized enzyme membrane and an electrode. Enzymes on immobilized enzyme membranes can specifically identify the analytes, catalyze the corresponding reaction changes, and trigger electrical signals. Since the enzyme has a high degree of specificity for the substrate, the material detected by the enzyme electrode differs depending on the enzyme on the membrane, and the sensor constituting it is different. But the only downside is that the enzyme's price is higher and its stability is slightly worse.
1.2.2 Immunosensors Immunosensors consist of antibodies or antigens and transducers and are used primarily for the detection of antigens or antibodies. When antigens and antibodies are combined, they can cause changes in the charges or groups that they carry, which can lead to changes in the signals that can be detected by the transducers, and can achieve the purpose of detecting the analytes.
1.2.3 Tissue/Microbial Sensors The activity and stability of enzymes in plant and animal tissues are higher than the isolated enzymes, and the materials are easily available and the preparation is simple. If the tissue skin of animals and plants is directly used as a sensor to prepare a biosensor, it becomes a tissue sensor. If the living microorganism is directly fixed on the surface of the electrode to make a sensor, it will become a microbial sensor. Microorganisms are more commonly used by bacteria and yeasts. At the same time, such sensors can also use microbial life activities (such as respiration) to detect the concentration of some metabolites. The disadvantage is that stability and selectivity have yet to be improved.
1.2.4 Nano-sensors Nano-sensors with biological probes that selectively bind target molecules are called nano-biosensors. Nanotechnology is the study of the structure and properties of substances at the nanoscale, and utilizes the science and technology of making materials with nanosized single atoms and molecules. Nanoscale biomaterials have unique chemical and physical properties such as surface effects, small size effects, and macroscopic quantum tunneling effects. Applying nanomaterials to biosensors can greatly improve the sensitivity and accuracy of biosensors and make detection more efficient. The introduction of platinum nanoparticles into the glucose oxidase electrode can improve the performance of the enzyme electrode and increase the current response value of the electrode by two orders of magnitude.
Nanotechnology is mostly involved in biosensor biomarkers, signal amplification, enzyme immobilization, and interference elimination techniques in the form of nanoparticles, nanodevices, and nanostructures. At present, there are many reports on nanosensors in the research report on nanosensors.
1.3 Advantages of biosensors Biosensors integrate modern biotechnology and electronic technology. Compared with traditional methods, biosensors have the following advantages: less sample detection and no need for pretreatment, no need to add other reagents, and can simultaneously complete the sample Separation and detection of the tested components; response to shaanxi, can be used repeatedly, and can achieve continuous online monitoring; instrument cost is low, easy to popularize.
2 Application of Biosensors for Detection of Pesticide Residues There are many biosensors currently used for the detection of pesticide residues in domestic biosensors, including enzyme sensors and immunosensors.
2.1 Enzyme Sensor 2.1.1 Biosensor Based on Enzyme Inhibition Principle This biosensor is mainly based on the inhibitory effect on cholinesterase and detects organophosphorus and carbamate pesticides in fruits and vegetables, but the inhibition is mostly irreversible inhibition; regeneration difficult. At present, studies report more on acetylcholine esters.
Acetylcholinesterase is widely present in animal tissues and blood, insect tissues and plants. Its main function is to rapidly hydrolyze acetylcholine to choline and acetic acid, ensuring effective delivery of choline. Organophosphorus and carbamate pesticides can specifically bind to acetylcholinesterase, inhibiting the activity of the enzyme, thereby preventing the hydrolysis of acetylcholine. When the enzyme is inhibited, the magnitude of the oxidation current can accurately reflect the extent to which the enzyme is inhibited, thereby detecting the concentration of the pesticide residue. As early as the 1950s, acetylcholinesterase has been used to detect pesticide residues.
Zhang Xianzhen and other biosensors using immobilized acetylcholinesterase as a recognition element to detect trichlorfon, trichlorfon is an organophosphate insecticide. After research, it was found that the frequency of the sensor was linearly related to the concentration of trichlorfon. The detection limit of trichlorfon was reduced to 2 nglml, and the detection time was less than that of the chromatographic method. Zhao Penglin et al. used immobilized butyrylcholinesterase BChE (EC 3.1.1.8) as a recognition element and a spectrophotometer as a transducer to construct a flow injection type BChE enzyme biosensor containing citrate buffer. Under liquid conditions, there is a good linearity in the concentration range of carbaryl in the range of 0.2-50 ug/ml. Zhang Shuping uses an nitrocellulose membrane with a pore size of 0.45 grn as the immobilized carrier. The acetylcholinesterase sensor and the national standard method respectively detect pesticide residues in fruit and vegetable samples that have been sprayed with the same amount of pesticide, and spray 10.0 mg/L of urethane. Pesticides formylcarbazole and 10.0 mg/L organophosphorus pesticide methamidophos. The results of the biosensor assay were 6.56 mg, L and 7.27 mg/L, respectively, which was slightly lower than that of the GC method. However, the detection time was only 30 minutes, which was obviously more promising than the GC method. Wei Fuxiang, etc. using acetylcholinesterase biosensor technology, apple, cucumber as a sample, using standard addition method for analysis, determination of organophosphorus pesticide residues in fruits and vegetables. The detection limits of malathion and methyl parathion were 4.80×10-11 and 2.93×10-10 mol/L, respectively.
The enzymatic sensing based on the principle of enzyme inhibition can use the method of immobilizing two kinds of enzymes at the same time, so that the sensor can simultaneously detect the various pesticides.
2.1.2 Biosensors Based on Enzymatic Hydrolysis Principle The commonly used hydrolases on biosensors are organic phosphate hydrolase (OPH), acid phosphohydrolase (OPAA) and parathionine hydrolase (PH). Reported more is organophosphorous hydrolase.
Organic Phosphoric Hydrolase (OPH) can hydrolyze organophosphorus pesticides, producing protons, ethanol and other products. These products can provide signals that can be detected to the relevant devices, and the transducers can then convert these signals into quantifiable light or electrical signals to detect the concentration of organophosphorus pesticides. At present, there are few domestic reports on such sensors, and there are many foreign ones.
Walker et al. developed a polymeric colloidal crystal hydrogel optical sensor that can be used to detect the concentration of parathion in methyl. The reaction of organophosphorus hydrolase (OPH) with methyl parathion produces a certain amount of protons and induces changes in the lattice and stability of the hydrogel. The sensor measures the concentration of methyl parathion by detecting this change. The lower limit of detection of methyl parathion in this sensor can be reduced to 0.2 umol/L. Zourob et al. used a pH-sensitive polymer and an organophosphorous enzyme to construct a magnetoelectric sensor that can detect organophosphorus pesticides in hydrogels. The concentration of pesticide residues was determined by measuring the change in pH caused by the hydrolysis of organophosphorus pesticides catalyzed by organophosphorus hydrolase. The sensor can successfully lower the limit of detection of paraoxon and parathion to 1×10-7 and 8.5×10-7 mol/L.
2.2 Immunosensors Immunosensors are easy to operate, have fast effects, and have good sensitivity and specificity. It mainly uses pesticides and specific antibody binding reactions to detect pesticides, herbicides and other pesticide residues in food and vegetables.
Yang Mingyan et al. constructed a DDT immunosensor based on self-assembled DDT antibody immobilization technology and dual-channel SAW detection technology. Tests have shown that under the static injection test method, the sensor has a high degree of sensitivity and high repeatability. In the detection range of 6×10-9 ug/L to 29×10-9 ug/L, the output frequency of the sensor changes. The concentration of DDT is in a good linear relationship. The detection limit for DDT can be reduced by 551.57 × 10-9 μg/L, and the response time is 40 min. Michele et al. used an herbicide atrazine-derived protein to construct an immunosensor capable of detecting atrazine concentration based on reflectance-absorption infrared spectroscopy. The sensor indirectly induces changes in the infrared signal through changes in anti-atrazine antibodies and antigen binding on the sensor, thus detecting the atrazine content. The test confirmed that the amount of atrazine detected by the sensor was exactly the same as that measured by the enzyme-linked immunosorbent assay under the same conditions. The Disperse Wave all-fiber immunosensor constructed by Long et al. can quickly detect the concentration of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), and can reduce the detection line of 2,4-D by 550.07ug. /L. The sensor can be reused for 100 detection cycles and is easy to carry, making it possible for the immune sensor to quickly detect pesticide residues on site.
3 Outlook Compared with foreign countries, China's biosensor research is relatively backward, and mainly focused on individual types of sensors, such as enzyme sensors, immune sensors. At the same time, biosensors are in good condition in laboratory conditions, but if they are to be widely used in industrial production, their stability, accuracy, and repeatability are the biggest problems that still need to be further improved.
The combination of biosensors and nanotechnology and computers has laid a foundation for the further improvement of sensors. Biosensors will tend to be miniaturized, multi-functionalized, and intelligent. They will be easier for people to carry and use. In the short-term, they will coexist with traditional detection methods. With the maturation of performance, biosensors have great development potential and have broad prospects in the rapid detection of food residue and pesticide residues.
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