Scientists from the University of São Paulo (USP) have created a wearable sensor device embedded in a synthetic rubber glove capable of detecting pesticide residues in food. The work, supported by Fapesp, was conceived and led by chemist Paulo Augusto Raymundo-Pereira, a researcher at the São Carlos Institute of Physics (IFSC-USP).
The device has three electrodes, located on the index, middle and ring fingers. They were printed on the glove by means of serigraphy, with a conductive carbon ink, and allow the detection of substances carbendazim (fungicide of the carbamate class), diuron (herbicide of the phenylamide class), paraquat (herbicide included in the list of bipyridinium) and phenitrothione (organophosphate insecticide). In Brazil, carbendazim, diuron and phenitrothione are used in cereal crops (wheat, rice, corn, soybeans and beans), citrus fruits, coffee, cotton, cocoa, bananas, pineapples, apples and sugar cane. The use of paraquat was banned in the country by the National Health Surveillance Agency (Anvisa).
The analysis can be done directly on liquids, just by dipping the fingertip containing the sensor into the sample, and also on fruits and vegetables, just by touching the surface of the sample.
Sergio Antonio Spinola Machado, professor at the São Carlos Institute of Chemistry (IQSC-USP) and co-author of the research, says that there is nothing similar on the market and that the methods most used today for the detection of pesticides are based on techniques such as chromatography ( mixture separation analysis), spectrophotometry (optical method of analysis used in biology and physical chemistry), electrophoresis (technique that uses an electric field to separate molecules) or laboratory tests.
“However, these methodologies are expensive, require specialized labor and a long time between analyzes and obtaining results. Sensors are an alternative to conventional techniques, because, based on reliable, simple and robust analyses, they provide fast, on-site and low-cost analytical information.”
In the glove created by the group, each finger is responsible for the electrochemical detection of a class of pesticide. Identification is made on the surface of the food, but in an aqueous medium. “We need water, because an electrolyte is needed [substância capaz de formar íons positivos e negativos em solução aquosa]. Just drop a drop on the food and the solution establishes contact between it and the sensor. The detection is done at the interface between the sensor and the solution”, details chemist Nathalia Gomes, a researcher at IQSC-USP and a member of the team.
sensors
The process of checking for the presence of pesticides is simple. One finger at a time is placed on the sample: first, the index finger; then the middle and finally the ring. In the case of a fruit juice, just dip your fingers in the liquid, one at a time. Detection is done in one minute and, in the case of the ring finger, in less than one minute.
“The sensor on the ring finger uses a faster technique. It is made up of a functionalized carbon electrode, while the other two fingers are made up of electrodes modified with carbon nanospheres.” [dedo indicador] and printex carbon, a specific type of carbon nanoparticle [dedo médio]. After detection, the data is analyzed by a software installed on the cell phone”, explains Raymundo-Pereira.
The researcher points out that the incorporation of carbon materials conferred selectivity to the sensors, one of the most important and difficult properties to achieve in similar devices. “A careful choice of carbon-based materials allowed the sensitive and selective detection of four classes of pesticides among the most used in agriculture: carbamates, phenylamides [subclasse das fenilureias], bipyridinium compounds and organophosphates. Thus, one of the differentials of the invention is the ability to selectively detect in the presence of other groups of pesticides, such as triazines, substituted glycine, triazole, strobilurin and dinitroaniline. With traditional methods this is not possible.”
Another highlight of the device is the possibility of direct detection, without requiring sample preparation, which makes the process fast. In addition, the method preserves the food, allowing consumption after analysis.
The glove has no expiration date and can be used as long as there is no damage to the sensors. Osvaldo Novais de Oliveira Junior, professor at IFSC-USP and co-author of the research, explains that sensors can be damaged by organic solvents (such as alcohol and acetone) or by some improper mechanical contact on the sensor surface (an object that scratches it, for example).
Market
Raymundo-Pereira emphasizes that the product is innovative and that the patent application process is already underway at the National Institute of Industrial Property (Inpi). He claims that there is no simple procedure for the detection of pesticides, which is the main reason why tests to discriminate different classes of pesticides and other contaminants are not yet available on the market. For him, the use of devices such as the glove, which allow the chemical analysis of hazardous materials in loco, would be relevant in food, environmental, forensic and security applications, allowing a quick decision-making process in the field.
“Representatives of international agencies that control the entry of food in different countries around the world already wear gloves to handle them. Imagine if they had a built-in pesticide sensing system? Foods containing prohibited pesticides would be discarded at the border. be used during harvest as well.”
According to the researcher, the cost of the device is basically the cost of the glove, without the sensor. “The sensors cost less than US$ 0.1. The main cost is the glove. We use a nitrile glove because it is less porous than the latex one. With the pandemic, the price of it has skyrocketed. And the individual cost has gone up. But still so the device we created is a very cheap product. More affordable than the tests done today.”
The research received funding from FAPESP through four projects (16/01919-6; 20/09587-8; 19/01777-5; and 18/22214-6).
O artigo Selective and sensitive multiplexed detection of pesticides in food samples using wearable, flexible glove-embedded non-enzymatic sensors pode ser acessado aqui.
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