“This new invention enables ultrasensitive detection of pesticide and veterinary drug residues,” said Assistant Prof. WANG Shu, a member of the team. 

The research results were published in Sensors and Actuators: B. Chemical.

Excessive pesticide and antibiotic use can cause neurotoxicity, endocrine disruption, and cancer. Therefore, developing affordable, convenient, and sensitive detection technology is crucial for food safety and sustainable agriculture. Immunochromatographic assays (ICA) are promising for on-site rapid detection due to their low cost and ease of use. However, their application for detecting trace-level small molecules is limited by insufficient sensitivity and semi-quantitative results.

In this study, researchers used polyethylenimine (PEI) self-assembly technology to prepare silica core double-layer quantum dot shell composite fluorescent labels. These labels can glow in three different colors: red, green, and blue.

The green and blue fluorescent labels were used as detection probes, while the red labels were used as encapsulation probes. This approach led to the development of a new competitive dual-channel CFICA. 

The system proved highly effective in detecting the antibiotic kanamycin (KAN) and the fungicide carbendazim (CBZ) in real samples like milk, tea, lake water, and soil. It’s at least 100 times more sensitive than current maximum residue limits (MRLs). 

They also created a handheld fluorescence reader to conveniently measure the multicolor signals on CFICA strips quantitatively.

“We believe this system has strong potential for practical applications,” said WANG Shu.

 CFICA and its technical principles (Image by WANG Shu)