Engineered E. coli biosensor with dual-module sensing and signal amplification for non-invasive detection of fecal bile acid salts in colorectal cancer screening.

In light of the growing global burden of colorectal cancer (CRC), there is an urgent need for sensitive and non-invasive diagnostic tools. Here, we developed a novel whole-cell biosensor in Escherichia coli for the specific detection of fecal bile acid salts as biomarkers linked to CRC progression. Our platform integrated two modular sensing architectures: a synthetic hammerhead ribozyme switch tailored for primary bile acids (100-300 μM), and an engineered two-component system (VtrA/VtrC) from Vibrio parahaemolyticus that selectively responded to secondary bile acid salts such as deoxycholic acid (50-300 μM). To achieve clinically meaningful sensitivity, we employed two signal amplification strategies, combining a constitutively expressed LuxR/pLuxI module with a tandem multi-reporter gene array, resulting in a roughly 2.7-fold increase in fluorescence output; the tandem multi-reporter gene array alone contributed to a roughly 1.7-fold increase in fluorescence output. Through systematic optimization, a biosensing platform capable of translating complex fecal biomarker profiles into quantifiable signals was established. This work demonstrates a significant advance toward a non-invasive, user-friendly, microbe-based point-of-care diagnostic system for personalized CRC risk assessment.