Fluorescent copper clusters with aggregation-induced emission enhancement effect for detecting Escherichia coli and Salmonella typhimurium

The cost-effective and label-free fluorescent sensor, which leverages a combination of glutathione-stabilized copper nanoclusters (GSH-CuNCs) and readily available copper ions (Cu 2+ ), presents a highly effective strategy for the selective and sensitive detection of Escherichia coli ( E. coli ) and Salmonella typhimurium ( S. typhimurium ). The sensor operates on the principle of aggregation-induced emission enhancement (AIEE), where the fluorescence of GSH-CuNCs is enhanced upon interaction with Cu 2+ . This enhancement is further modulated by the reduction of Cu 2+ by E. coli and S. typhimurium through a copper-homeostasis mechanism, allowing for the detection of these bacteria. The sensor demonstrates a linear response to E. coli and S. typhimurium over a concentration range of 10 3 to 10 7 cfu mL −1 . The detection limits for these bacteria are determined to be 111 cfu mL −1 for E. coli and 130 cfu mL −1 for S. typhimurium , respectively. The practical utility of the sensor has been confirmed through its successful application in detecting these bacterial strains in complex samples such as eggshell and popsicle matrices, showcasing its potential for real-world food safety monitoring.