Copper Ion Genetic Biosensor: A Synthetic Biology Approach for Environmental Heavy Metal Detection

Excess environmental copper from industrial and agricultural sources poses significant risks to ecosystems and human health. We engineered a whole-cell Escherichia coli biosensor to rapidly detect bioavailable Cu(II) ions using a copper-inducible genetic circuit. The system couples the E. coli copA promoter – a copper- responsive regulatory element – to a green fluorescent protein (GFP) reporter gene, producing a quantifiable fluorescence signal in the presence of copper. We constructed the sensor on a plasmid and transformed it into E. coli; subsequent assays measured GFP fluorescence across a gradient of copper concentrations. The biosensor responded to Cu(II) in a dose-dependent manner, with a detection threshold of ~ 10 µM and a linear dynamic range up to ~ 100 µM. It demonstrated specificity for copper over other common metal ions, and maintained performance in spiked environmental water samples. Time-course experiments further showed that detectable fluorescence could be induced within hours of exposure. These results underscore the potential of synthetic biology for creating cost-effective, field-deployable heavy metal detectors. Our engineered copper biosensor offers real-time, in situ monitoring capability and could be expanded or optimized for improved sensitivity and broader heavy-metal detection. We discuss its strengths and limitations relative to existing methods, and propose future enhancements – such as circuit modifications and cellular engineering – to meet stringent environmental regulatory standards. This work provides a proof- of-concept for deploying genetically engineered whole-cell sensors as practical tools for environmental monitoring of heavy metal contamination.