Researchers at the Karolinska Institutet in Sweden have developed a tiny sensor to detect pesticides on fruit in minutes. The technique, described as proof-of-concept in a journal article Advanced science, uses flame-sprayed silver nanoparticles to boost the signal of chemicals. Although still in an early stage, the researchers hope these nanosensors can help detect food pesticides before consumption.
“Reports show that up to half of all fruit sold in the EU contains pesticide residues which in larger quantities have been linked to human health problems,” says Georgios Sotiriou, principal investigator in the Department of Microbiology, Cancer Biology and of cells, Karolinska Institutet, and the corresponding author of the study. “However, current techniques for detecting pesticides on individual products before consumption are in practice limited by the high cost and cumbersome manufacturing of its sensors. To overcome this, we have developed inexpensive and reproducible nanosensors that could be used to monitor traces. of fruit pesticides for example at the store. “
The new nanosensors use a 1970s discovery known as surface-enhanced Raman scattering, or SERS, a powerful sensing technique that can increase the diagnostic signals of biomolecules on metal surfaces by more than 1 million times. The technology has been used in several research fields, including chemical and environmental analyzes, as well as to detect biomarkers for various diseases. However, high production costs and limited batch-to-batch reproducibility have so far hindered widespread application in food safety diagnostics.
Flame spray technology
In the present study, the researchers created an SERS nanosensor using flame spray, an established and inexpensive technique for depositing the metal coating, to deliver tiny droplets of silver nanoparticles onto a glass surface.
“The flame spray can be used to rapidly produce uniform SERS films over large areas, removing one of the key obstacles to scalability,” says Haipeng Li, postdoctoral researcher in Sotiriou’s lab and first author of the study.
The researchers then fine-tuned the distance between the individual silver nanoparticles to improve their sensitivity. To test their substance sensing ability, they applied a thin layer of tracer dye over the sensors and used a spectrometer to discover their molecular fingerprints. The sensors reliably and uniformly detected molecular signals and their performance remained intact when they were tested again after 2.5 months, which underscores their shelf life potential and feasibility for large-scale production. , according to the researchers.
Pesticides detected on apples
To test the practical application of the sensors, the researchers calibrated them to detect low concentrations of parathion-ethyl, a toxic agricultural insecticide that is banned or restricted in most countries. A small amount of parathion-ethyl was placed on one part of an apple. The residues were subsequently collected with a cotton swab which was dipped in a solution to dissolve the pesticide molecules. The solution was dropped onto the sensor, which confirmed the presence of pesticides.
“Our sensors are able to detect pesticide residues on apple surfaces in a short five-minute time frame without destroying the fruit,” says Haipeng Li. “Although they need to be validated in larger studies, we offer a practical proof-of-concept application for large-scale pre-consumption food safety testing.”
Next, the researchers want to explore whether nanosensors can be applied to other areas such as the discovery of disease-specific biomarkers at the point of care in resource-limited settings.
The research was funded by the European Research Council (ERC), the Karolinska Institutet, the Swedish Foundation for Strategic Research (SSF) and the Swedish Research Council.
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