Ratiometric fluorescence detection of tetracycline for tetracycline adjuvant screening in bacteria

Persistent generation of tetracycline (TC) resistant bacteria poses serious risks for public health. It is of great importance to develop a strategy for rapid screening TC adjuvants for restore TC-susceptibility against resistant bacteria. Herein, a flower-like europium-doped nanoprobe is created by coordinating Eu3+ with adenine (Ade)-graphitic carbon nitride (g-C3N4) conjugate (g-C3N4-Ade-Eu). TC quenches the intrinsic fluorescence of g-C3N4 at 436 nm via internal filter effect (IFE), and meanwhile the antenna effect (AE) of TC significantly promotes the emission of Eu3+ at 618 nm. These fluorescence responsive behaviors of g-C3N4-Ade-Eu ensure ratiometric fluorescence assay of TC within 0.01 − 10 μM, along with a limit of detection (LOD) of 5.0 nM. The nanoflower structure exhibits large surface area, which endows enrichment of TC on the flower surface to ensure a high assay sensitivity. Tetracycline in bacteria is quantified for the first time by this protocol, and it further facilitates the rapid screening (∼3 h) of tetracycline adjuvants in E.coli ER2738.