Cell-based biosensors have great potential to detect various toxic and pathogenic contaminants in aqueous environments. However, frequently they cannot meet practical requirements due to insufficient sensing performance. To address this issue, we investigated a modular, cascaded signal amplifying methodology. We first tuned intracellular sensory receptor densities to increase sensitivity, and then engineered multi-layered transcriptional amplifiers to sequentially boost output expression level. We demonstrated these strategies by engineering ultrasensitive bacterial sensors for arsenic and mercury, and improved detection limit and output up to 5,000-fold and 750-fold, respectively. Coupled by leakage regulation approaches, we developed an encapsulated microbial sensor cell array for low-cost, portable and precise field monitoring, where the analyte can be readily quantified via displaying an easy-to-interpret volume bar-like pattern. The ultrasensitive signal amplifying methodology along with the background regulation and the sensing platform will be widely applicable to many other cell-based sensors, paving the way for their real-world applications.
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All data and plasmids supporting the findings are available from the corresponding author upon reasonable request.
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We thank M. Billah (Khulna University) and his colleagues for facilitating our collections of groundwater samples in Bangladesh. This work was supported by UK BBSRC project grant (no. BB/N007212/1), Leverhulme Trust research grant (no. RPG-2015-445), Wellcome Trust Seed Award in Science (no. 202078/Z/16/Z) and EPSRC/BBSRC Global Challenges Research Fund Awards. X.W. was supported by scholarships from the China Scholarship Council and Scottish Universities Life Sciences Alliance. F.V., E.P. and S.J.M. were supported by the Ecole Polytechnique Federale de Lausanne, a Swiss National Science Foundation Grant (no. CR23I2 140697) and a SystemsX.ch Special Opportunity Grant (no. 2015/325).
B.W. and X.W. filed a patent application based on the technology invention in this work.
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Wan, X., Volpetti, F., Petrova, E. et al. Cascaded amplifying circuits enable ultrasensitive cellular sensors for toxic metals. Nat Chem Biol 15, 540–548 (2019). https://doi.org/10.1038/s41589-019-0244-3
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