A label-free optical whole-cell Escherichia coli biosensor for the detection of pyrethroid insecticide exposure

Authors: RIANGRUNGROJ, PINPUNYA - Imperial College; Bever, Candace; HAMMOCK, BRUCE - University Of California, Davis; POLIZZI, KAREN - Imperial College

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2019
Publication Date: 8/28/2019
Citation: Riangrungroj, P., Bever, C.R., Hammock, B.D., Polizzi, K.M. 2019. A label-free optical whole-cell Escherichia coli biosensor for the detection of pyrethroid insecticide exposure. Scientific Reports. 9:12466. https://doi.org/10.1038/s41598-019-48907-6.
DOI: https://doi.org/10.1038/s41598-019-48907-6

Interpretive Summary: Pyrethroids insecticides are chemicals used in agriculture. Human exposure to these insecticides is indicated by the presence of a metabolite, 3-phenoxybenzoic acid (3-PBA), often found in urine or plasma. Low-cost, portable technologies for the detection of harmful chemicals are needed to help protect environment and human health. In this work, we describe a cell-based assay used to detect 3-PBA. The assay can be run in as little as 30 minutes, detect as low as 3 ng/mL in urine or plasma, and the cells can be stored for 90 days without loss of functionality. Our whole-cell biosensor concept has potential to be further developed as a screening tool for monitoring the exposure to pyrethroids as it is simple, low cost, and portable.

Technical Abstract: There is a growing need for low-cost, portable technologies for the detection of threats to the environment and human health. Here we propose a label-free, optical whole-cell Escherichia coli biosensor for the detection of 3-phenoxybenzoic acid (3-PBA), a biomarker for monitoring human exposure to synthetic pyrethroids insecticides. The biosensor functions like a competitive ELISA but uses whole-cells surface displaying an anti-3-PBA VHH as the detection element. When the engineered cells are mixed with 3-PBA-protein conjugate crosslinking that can be visually detected occurs. Free 3-PBA in samples competes with these crosslinks, leading to a detectable change in the output. The assay performance was improved by coloring the cells via expression of the purple-blue amilCP chromoprotein and the VHH expression level was reduced to obtain a limit of detection of 3 ng/mL. The optimized biosensor exhibited robust function in complex sample backgrounds such as synthetic urine and plasma. Furthermore, lyophilization enabled storage of biosensor cells for at least 90 days without loss of functionality. Our whole-cell biosensor is simple, low-cost, and portable and therefore has potential to be further developed as a screening tool for monitoring exposure to pyrethroids in low-resource environments.