A group of researchers from the prestigious Karolinska Institute in Sweden has developed a nanosensor made with silver nanoparticles capable of detecting pesticides in fruit in just five minutes. The sensor is still in its early stages, and scientists hope it will help us discover the presence of pesticides in food before we eat it. The article has been published in the journal Advanced Science .
“Reports show that up to half of the fruits sold in the EU contain pesticide residues which, in large quantities, have been linked to human health problems,” says Georgios Sotiriou, Principal Investigator at the Department of Microbiology, Tumors and Cell Biology of the Karolinska Institute, and author of the study. “However, current techniques for detecting pesticides in individual products before consumption are limited in practice by the high cost and cumbersome fabrication of their sensors. To overcome this, we developed cheap and reproducible nanosensors that could be used to monitor traces of pesticides in the fruit, for example, in the store”.
The nanosensors in this study base their operation on surface-enhanced Raman scattering, or SERS , a powerful detection technique he developed in the 1970s that can increase diagnostic signals from biomolecules on metal surfaces by more than a million times. times. Not surprisingly, this technology has been used in various fields of research, such as chemical and environmental analysis, as well as to detect biomarkers of various diseases. However, high production costs and limited lot-to-lot reproducibility have so far hampered its widespread application in the field of food safety.
flame spraying
The researchers created the SERS nanosensor using flame spray. This is a well-known and cost-effective technique used to deposit metallic coatings. In this case, small drops of silver nanoparticles have been deposited on a glass surface . “Flame spray can be used to rapidly produce uniform SERS films over large areas, removing one of the main barriers to scalability,” says Haipeng Li, who has also participated in the study.
The researchers then adjusted the distance between the silver nanoparticles to improve their sensitivity. To test their ability to detect substances, they applied a thin layer of tracer dye to the sensors and used a spectrometer to discover their molecular fingerprints. According to the researchers, the sensors reliably and consistently detected molecular signals and their performance remained intact when retested after 2.5 months, underscoring their potential longevity and feasibility for large-scale production. .
Pesticide detection in apples
To test the sensors, the researchers calibrated them to detect low concentrations of ethyl parathion , a toxic agricultural insecticide that is banned or restricted in most countries. A small amount of parathion-ethyl was placed on part of an apple. Subsequently, the residues were collected with a cotton swab that was immersed in a solution to dissolve the pesticide molecules. The solution was dropped onto the sensor, which confirmed the presence of pesticides.
“Our sensors can detect pesticide residues on the surface of apples within five minutes without destroying the fruit ,” says Haipeng Li. “Although they need to be validated in larger studies, we offer a practical application proof of concept for food safety testing at pre-consumer scale.”
The researchers’ next goal is to see if nanosensors can be applied to other areas, such as biomarker discovery for specific diseases in resource-limited settings.
Referencia: Haipeng Li, Padryk Merkl, Jens Sommertune, Thomas Thersleff, and Georgios A. Sotiriou. 2022. SERS Hotspot Engineering by Aerosol Self-Assembly of Plasmonic Ag Nanoaggregates with Tunable Interparticle Distance. Advanced Science. DOI: 10.1002/advs.202201133
