Development of a Core-Shell-Encapsulated Biosensor for On-Site Detection of Trace Chlorpyrifos

Chlorpyrifos, a broad-spectrum organophosphorus pesticide, accumulates persistently in the environment and food chain, posing significant risks to ecosystems and human health. Whole-cell biosensors offer a promising alternative for on-site pesticide detection. However, their practical application is hindered by insufficient sensitivity for trace residues and biosafety concerns. Here, we developed a core-shell hydrogel-encapsulated whole-cell biosensor for the sensitive and safe detection of trace-level chlorpyrifos. A metabolic module was integrated into the basic ChpR-P_chpA genetic circuit to enhance sensitivity through signal amplification. This was realized through an enzymatic transformation of weakly activating substrates into derivatives with strong activating potential. This approach amplified the output signal and lowered the detection limit by 32-fold to 0.75 nM, meeting the stringent regulatory thresholds for chlorpyrifos residues. Furthermore, a physical containment approach based on core-shell hydrogel microbeads effectively prevented bacterial escape while maintaining high cell viability and sensing performance. The encapsulated biosensor remained active over 30 days of storage and showed reliable performance in real vegetable, water, and soil samples with satisfactory recoveries. This work provides a robust, field-deployable, and environmentally safe platform for monitoring trace chlorpyrifos residues in complex environmental matrices.