Simple and Cost-effective Fluoride Riboswitch-Based Whole-Cell Biosensor for the Determination of Fluoride in...

Fluoride in drinking water poses health risks when exceeding WHO-recommended limits, necessitating accurate detection methods. This study developed a highly selective fluoride riboswitch (FRS)-based whole-cell biosensor using an E. coli mutant with a recombinant plasmid carrying the FRS fused to the lacZ reporter gene. Fluoride binding to the FRS aptamer triggers β-galactosidase expression, enabling fluoride quantification by a colorimetric assay. Using a calibration curve (R² > 0.9), fluoride concentrations in Sri Lankan water samples were determined (0.15-0.90 ppm). Minimal interference from common ions (Cl⁻, OH⁻, Na⁺, K⁺, Ca²⁺, CO₃²⁻, HCO₃⁻, and NO₃⁻) confirmed the biosensor's narrow specificity and high selectivity towards fluoride.