A novel fluorescent sensing system based on pH-responsive carbon dots for the identification and detection of bacteria

Identifying and detecting bacteria are crucial for ensuring food safety and environmental monitoring. We have developed a detection system based on pH-responsive fluorescent carbon dots (pH-CDs). This system leverages the fact that Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) exhibit significantly higher sugar metabolism capabilities compared to other foodborne pathogens, enabling the identification and detection of S. aureus and E. coli. As the pH of the solution increased from 3 to 7.5, the fluorescence intensity of the pH-CDs gradually decreased. In the presence of glucose and lactose, S. aureus and E. coli participated in metabolic processes, which converted these sugars into acidic products, thereby inducing a reduction in the solution pH. The decrease in pH, in turn, triggered an enhancement in the fluorescence intensity of pH-CDs. Therefore, the pH-CD sensor enabled quantitative detection of S. aureus and E. coli with a robust linear response (R² > 0.99), detection limits of 3–6 CFU mL⁻¹, and reliable recoveries of 97–102% in real water samples, confirming its suitability for application. Furthermore, pH-CDs can also be utilized to identify S. aureus and E. coli, which differ in their capacity to metabolize lactose. The proposed fluorescent sensing system provides a novel approach for the rapid identification and quantification of S. aureus and E. coli, holding significant potential for practical applications.