Researchers at the Karolinska Institutet in Sweden developed a new nano-sensor for detecting pesticides on produce in a matter of minutes. A study published in the journal Advanced Science outlines how the nano-sensors use flame-sprayed nanoparticles to increase the signal of chemicals. While still at an early stage, the researchers hope these nano-sensors could help uncover pesticides before consumption.
“Current techniques for detecting pesticides on single products before consumption are restricted in practice by the high cost and cumbersome manufacturing of its sensors,” said Georgios Sotiriou, the study’s corresponding author. “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.”
The nano-sensors are based on a 1970s discovery known as surface-enhanced Raman scattering (SERS), a powerful sensing technique that can increase the diagnostic signals of biomolecules on metal surfaces by more than one million times. Though the technology has been used in several research fields, limited batch-to-batch reproducibility and high production costs have delayed its widespread application in food safety.
Now, researchers at the Karolinska Institutet created SERS nano-sensors by using a flame spray made from silver that delivered small droplets of nanoparticles onto a glass surface. To test their substance-detecting ability, the researchers applied a thin layer of tracer dye on top of the sensors and used a spectrometer to uncover their molecular fingerprints.
The nano-sensors reliably and uniformly detected the molecular signals and their performance remained intact when tested again after over two months. Next, the researchers tested the sensors’ practical application, finetuning them to detect low concentrations of parathion-ethyl, a toxic agricultural insecticide that is restricted by the US Environmental Protection Agency (EPA).
A small amount of the insecticide was placed on part of an apple. The residues were later collected with a cotton swab that was immersed in a solution to dissolve the pesticide molecules. The solution was then dropped on the sensor, which confirmed the presence of pesticides. The researchers noted that the process took around five minutes and the apple remained intact.
So, why is it important to detect pesticides on food before consumption? Last month, an American activist group called the Environmental Working Group (EWG) announced its annual Dirty Dozen List, a list of the most pesticide-contaminated fresh produce based on the latest tests by the US Department of Agriculture (USDA) and US Food and Drug Administration (FDA). The top offenders included strawberries, spinach, leafy greens, apples, grapes and nectarines.
In Europe, Pesticide Action Network (PAN) Europe conducted a nine-year study with government data, analyzing 100,000 popular homegrown fruit samples. The study found that a third of apples and half of all blackberries that were tested had residues of the most toxic categories of pesticides. Some of them have been linked to illnesses such as birth deformities, cancer and heart disease.
The researchers are planning to explore more potential applications of the new nano-sensors, such as using the nano-sensors to discover biomarkers for specific diseases at the point of care in resource-limited settings.