DNA-AgNPs@Hydrogel microneedle-based flexible biosensor for rapid detection of thiram

Thiram, a representative dithiocarbamate pesticide, has been widely applied in agriculture to prevent fungal infections in crops. However, its excessive residues in food and aquatic products pose serious health risks, including hepatotoxicity, nephrotoxicity, and neurotoxicity. Conventional detection techniques such as chromatography and mass spectrometry, though accurate, require complex instrumentation, skilled operation, and laboratory conditions, making them unsuitable for on-site testing. Therefore, there is an urgent need to develop a portable, rapid, and sensitive sensing platform capable of in-situ detection to ensure food safety and environmental protection in real-world settings.

To address this challenge, we fabricated a flexible fluorescent hydrogel microneedle biosensor (PAAP) by embedding DNA-AgNPs into a polyacrylamide (PAAm) hydrogel matrix. The incorporation of DNA-AgNPs provided stable probe immobilization and enhanced fluorescence response. Upon exposure to thiram, the fluorescence of the hydrogel was significantly quenched, enabling rapid and highly sensitive visual detection with a detection limit of 6.57 nM. The PAAP hydrogel displayed excellent mechanical flexibility, biocompatibility, and environmental stability, allowing conformal contact with curved biological surfaces such as fish skin. Moreover, the sensor maintained strong anti-interference capability against coexisting ions and organic substances, and could be easily adapted into patch-like or microchip configurations for field applications, demonstrating robust reliability in complex sample environments.

This work provides a novel and practical approach for in-situ and field-deployable pesticide detection. The integration of fluorescent DNA-AgNPs and flexible hydrogel architecture enables non-destructive, real-time analysis on biological surfaces. Such a design holds great promise for ensuring food quality control, promoting environmental monitoring, and advancing the development of next-generation smart sensing technologies for public health protection.