Over the past decade, contamination of fresh fruits by the most hazardous pesticides has increased significantly across Europe, according to a study that took place over a period of nine years. This raises concerns for consumers as some of those toxic pesticides detected are linked to serious illnesses such as cancers, heart disease, and birth deformities.
Image Credit: Haipeng Li and Georgios A Sotiriou. News.ki.se. (2022) Nano-sensor detects pesticides on fruit in minutes. [online] Available at: https://news.ki.se/nano-sensor-detects-pesticides-on-fruit-in-minutes
Now, a team of scientists at Karolinska Institutet has created a proof-of-concept nanosensor that has the capability to rapidly detect the levels of pesticides on fruit. Published in the journal Advanced Science, the team use flame-sprayed silver nanoparticles to enhance the chemical signal of the pesticides.
One of the issues is that testing for pesticides on single products prior to consumption is impeded by the high cost and laborious manufacturing of sensors.
To overcome this, we developed inexpensive and reproducible nano-sensors that could be used to monitor traces of fruit pesticides at, for example, the store.
Georgios Sotiriou, Principal Researcher, Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet
Enhanced Sensing Technique
The innovative nanosensors developed by the team use surface-enhanced Raman scattering, or SERS, a highly influential sensing technique that can enhance biomolecule diagnostic signals on the surface of metals by over 1 million times.
As of now, the technology has been deployed in a number of research fields, including environmental and chemical analysis, as well as to identify key biomarkers for diseases. Yet, food safety diagnostic applications have been held back by insufficient batch-to-batch reproducibility and expensive costs of production.
To create a practical SERS nanosensor, the research team used the flame-spraying technique of applying a metal coating to a suitable substrate.
The flame spray can be used to quickly produce uniform SERS films across large areas, removing one of the key barriers to scalability.
Haipeng Li, Postdoctoral Researcher, Sotiriou’s Lab
To boost the sensitivity of the nanosensor, Li and the team carefully adjusted the spacing between different silver nanoparticles. A spectrometer was used to uncover the molecular fingerprint and test the detectability of the technology.
Proof-of-Concept
It was discovered that the sensors were able to discern the molecular signals with good reliability, and when tested again – 2-3 months later – the performance of the nanosensors was still strong, demonstrating the potential for scalability.
To further test the practical use of the nanosensors, they were calibrated to detect low levels of the pesticide parathion-ethyl, which is on the restricted or banned list in most nations.
By placing just a tiny amount of parathion-ethyl on an apple and then swabbing the sample, the researchers tested the technology by dropping a solution mixed with the sample onto the nanosensor.
As a proof-of-concept for realistic practical application, the presence of pesticide was detected on the surface of fresh fruits, demonstrating that such SERS films may enhance food safety sensing at the point of consumption.
“Our sensors can detect pesticide residues on apple surfaces in a short time of five minutes without destroying the fruit,” says Li.
While they need to be validated in larger studies, we offer a proof-of-concept practical application for food safety testing at scale before consumption.
Haipeng Li, Postdoctoral Researcher, Sotiriou’s Lab
The researchers are now hoping to take their research to the next level by seeing if the nanosensors have practical applications beyond monitoring food products for levels of pesticides. The team believes that it has potential use in the field of biomarker research in diseases.
References and Further Reading
PAN Europe. (2022) Forbidden fruit: The dramatic rise in dangerous pesticides found on fruits and vegetables sold in Europe and evidence that governments are failing their legal obligations. [online] Available at: https://www.pan-europe.info/resources/reports/2022/05/forbidden-fruit-dramatic-rise-dangerous-pesticides-found-fruits-and
Li, H., Merkl, P., Sommertune, J., Thersleff, T. and Sotiriou, G., (2022) SERS Hotspot Engineering by Aerosol Self‐Assembly of Plasmonic Ag Nanoaggregates with Tunable Interparticle Distance. Advanced Science, p.2201133. Available at: https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202201133
News.ki.se. (2022) Nano-sensor detects pesticides on fruit in minutes. [online] Available at: https://news.ki.se/nano-sensor-detects-pesticides-on-fruit-in-minutes
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