Sugar-metabolism-triggered pathogenic bacteria identification based on pH-sensitive fluorescent carbon dots

Rapid distinguishing of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with high sensitivity is critical for human health. Herein, a smart sugar-metabolism-triggered E. coli and S. aureus identification strategy is established on the basis of pH-sensitive fluorescent carbon dots (p-CDs). The fluorescence of the prepared pCDs depends linearly on the solution pH in the acidic range from 4.0 to 7.0. When p-CDs are introduced into aqueous solutions that contain bacteria and sugar molecules, such as glucose or lactose, the fluorescence readout is reduced due to the acidic substances that are produced in the glucometabolic process of bacteria toward sugar molecules, which can decrease the pH of the sensing system. More importantly, E. coli and S. aureus differ in terms of their sugar metabolic capability on lactose and thus can lead to distinguishable fluorescence signals, which are used to further distinguish E. coli from S. aureus. The detection limits (LODs) for E. coli and S. aureus are 21 CFU mL(-1) and 33 CFU mL(-1), respectively, in the presence of glucose and 762 CFU mL(-1) for E. coli in the presence of lactose. This p-CD-based fluorescence approach is simple, sensitive and free of any modification steps; thus, it has a much broader field of potential applications than other approaches.