A research team led by the Karolinska Institute in Sweden has developed a tiny sensor which can detect pesticides on fruits very quickly, in just a few minutes. This innovative technique uses flame-sprayed nanoparticles made from silver to increase the signals from chemicals. Although these nano-sensors are still at a relatively early stage of development, the scientists hope that they could be soon used by consumers worldwide to quickly detect food pesticides.
“Reports show that up to half of all fruits sold in the EU contain pesticide residues that in larger quantities have been linked to human health problems,” said study senior author Georgios Sotiriou, an expert in Microbiology, Tumor and Cell Biology at the Karolinska Institute.
“However, current techniques for detecting pesticides on single products before consumption are restricted in practice by the high cost and cumbersome manufacturing of its 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.”
In designing these sensors, Professor Sotiriou and his team employed a 1970s discovery known as surface-enhancing Ramon scattering (SERS) – a powerful sensing technique which can increase the diagnostic signals of biomolecules on metal surfaces by over one million times – and used flame spray to deliver small droplets of silver nanoparticles onto a glass surface.
“The flame spray can be used to quickly produce uniform SERS films across large areas, removing one of the key barriers to scalability,” explained study lead author Haipeng Li, a postdoctoral researcher in Professor Sotiriou’s lab. The scientists then fine-tuned the distance between the individual silver nanoparticles to enhance their sensitivity. Repeated tests showed that the sensors reliably and uniformly detected molecular signals for at least 2.5 months, a feature underscoring their shelf life potential and feasibility for large-scale production.
To test whether the sensors can reliably detect pesticides, the researchers placed low concentrations of parathion-ethyl (a toxic agricultural insecticide banned in many countries) on part of an apple.
“Our sensors can detect pesticide residues on apple surfaces in a short time of five minutes without destroying the fruit,” Dr. Li reported. “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.”
In future research, the scientists aim to explore whether these nano-sensors can be applied to other areas, such as discovering biomarkers for specific diseases in resource-limited settings.
The sensors are described as a proof-of-concept in an article published in the journal Advanced Science.