Multichannel Bioelectronic Sensing: Binary Encoding of Environmental Contaminants
Authors: Zhang Xu , Charrier Marimikel , Ajo-Franklin Caroline M 
Published: December 2024

Environmental water contamination from natural and synthetic chemicals is a pressing global issue. Addressing this requires the development of portable, selective, and accurate sensors. Biosensors, particularly whole-cell bioelectronic sensors, are promising due to their ability to convert chemical signals into electrical signals via extracellular electron transfer (EET) pathways. However, these sensors typically employ a single electron transfer pathway as an electrochemical channel, limiting them to the detection of a single analyte (Atkinson et al. 2022).
To expand the information content, we have developed a multichannel sensor where different chemicals regulate distinct EET pathways within a single Escherichia coli cell. One channel utilizes the flavin synthesis pathway from Bacillus subtilis (Yang Yun et al. 2017) and is controlled by a cadmium-responsive promoter (Hui et al. 2021). Another channel, the Mtr pathway from Shewanella oneidensis (Ross Daniel E. et al. 2007), is controlled by an arsenite-responsive promoter (Chen et al. 2019) through activation of cytochrome CymA expression. We exploit the differing redox potentials of these two EET pathways (Kracke, Vassilev, and Krömer 2015) to develop a redox-potential-dependent algorithm that efficiently converts analog current curves into 2-bit binary outputs. This enables our bioelectronic sensor to detect and differentiate heavy metals at EPA limits. When deployed in complex environmental water samples with lower electroactivities, our sensor effectively and accurately encodes 2-bit binary signals across various analyte conditions. Thus, our multichannel bioelectronic sensor advances the field through simultaneous detection of different chemicals by a single cell, significantly expanding information transmission from EET and helping to safeguard human and environmental health.
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