Discrimination of pathogenic bacteria with boronic acid modified protonated g-C3N4 nanosheets at various pHs

Rapid and accurate identification of pathogenic bacteria remains a major challenge, especially for antibiotic-resistant bacteria. In this work, a novel sensing array for the discrimination of pathogenic bacteria based on the distinctive properties of boronic acid-functionalized graphitic carbon nitride nanosheets ((+)BA-g-CN) at various acidities was constructed. Bacteria cells were attached on (+)BA-g-CN either through the electrostatic interaction or the affinity between boronic acid on the nanosheets and saccharide unit on the surface of pathogenic bacteria at various pHs. Both of these interactions can lead to the sedimentation of the composites of bacteria- (+)BA-g-CN, causing the decrement in fluorescence intensity of the supernatant. For different types of bacteria, the degree of fluorescence decrement varies at various pHs, which provides a promising way for the discrimination of pathogenic bacteria. Nine types of pathogenic bacteria, i.e., six kinds of Gram-negative bacteria and three kinds of Gram-positive bacteria were well discriminated by the sensing array with linear discriminant analysis (LDA) at OD600 = 0.01. Its practical application is further demonstrated by the identification of different growth stages of bacteria and the discrimination of pathogenic bacteria in human urine.