A fluorescent biosensor based on boronic acid functionalized carbon dots for identification and sensitive detection of Gram-positive bacteria

Rapid distinguishing and detection of Gram-positive and Gram-negative bacteria with high sensitivity is essential for human health worldwide. Herein, an excellent fluorescence biosensing platform for bacterial identification and detection is constructed on the basis of boronic acid functionalized carbon dots (B-CDs). The B-CDs fluorescence probes were tightly attached to the bacterial surface through the interaction of the boronic acid group with glycolipids on the outside of bacterial cells. Our experimental results showed that the B-CDs displayed a stronger binding ability toward Gram-positive bacteria, enabling the specific detection of Gram-positive bacteria. More importantly, Gram-positive bacteria and Gram-negative bacteria differ in terms of their saccharide units on the cell wall, resulting in distinct fluorescence signals, which could be employed for distinguishing Gram-positive and Gram-negative bacteria. Taking S. aureus as a representative of Gram-positive bacteria, the results showed that the linear range of detection was 2.6 × 10¹-5.2 × 10⁶ CFU mL⁻¹ and the detection limit was 7 CFU mL⁻¹. Our research provides great potential for further development of a novel platform for bacterial determination and identification.