Development of a fluorescent chemosensor for chloride ion detection in sweat using Ag+-benzimidazole complexes

The level of chloride ions (Cl⁻) in sweat is a recognized biomarker for the genetic disorder cystic fibrosis (CF). The accurate quantitation of chloride ions in sweat is therefore a vital diagnostic tool for this life-threatening disease. In this work, a fluorescent, chloride ion chemosensor was developed by exploiting the strong interaction between silver (Ag+) and chloride ions. Using the concept of ligand displacement, six Ag+-benzimidazole complexes were prepared as candidate chloride ion chemosensors. The Ag+-2-(Furan-2-yl)-1H-benzo[d]imidazole (Ag+-FBI) complex was identified as the optimal sensor owing to its Ag+-FBI high sensitivity (limit of detection = 19 μM), short response time (<3 min), and remarkable fluorescence turn-on response across a broad pH range (pH 6–9). The Ag+-FBI complex exhibited high selectivity for Cl⁻ ions and was successfully used to quantify chloride ions in artificial sweat samples containing multiple ions and other biological constituents. This unique, simple, and effective probe thus shows great potential for clinical diagnostic applications.