Array-based specific classification of bacterial species via the redox state transition of riboflavin

We observed redox state transitions of riboflavin (Rf) upon incubation with gram-positive (G+) or gram-negative (G-) bacteria. The consequent transitions based on the proton-coupled electron transfer (PCET) reaction alters the reducibility and oxidability of Rf, providing a novel mechanism for specific classification of G- and G + bacterial species and discrimination of different bacterial strains. Thus, a colorimetric/fluorometric sensor array based on silver nanotriangles (AgNTs) and Rf was established, offering dosimetric identification of 14 bacterial and 12 mixed bacterial samples. G- and G+ bacteria could be easily classified by the color change in AgNTs; different bacterial strains were also well discriminated via the fluorescent variation of Rf. This rapid and efficient sensor array with dual detection modalities provides a biochemical mechanism for the rapid differentiation of bacterial species and strains and presents potential applications in both clinical microbiology and bacteriology.