A bismuth-based MOF proportional fluorescence sensor for the rapid and sensitive detection of an anthrax biomarker†

Bacillus anthracis is a highly dangerous zoonotic pathogen that poses a considerable threat to public health. Rapid and accurate detection of the biomarker 2,6-pyridinedicarboxylic acid (DPA) is necessary for the effective prevention and treatment of infections caused by this microorganism. Here, a new method for detecting DPA using a bi-emission ratio fluorescence sensor based on a bismuth organic skeleton (Bi-MOF) is developed. The dual-emission ratio fluorescent sensor (Eu@Bi-MOF) is prepared by Eu³⁺ functionalizing Bi-MOF, synthesized through using bismuth nitrate as the metal node and 1,3,5-phenyltricarboxylic acid as the ligand, with a post-synthetic modification method and exhibits a sensitive fluorescent response to DPA. In the presence of DPA, the fluorescence intensity of the Eu@Bi-MOF sensor at 438 nm remains unchanged, while the red fluorescence emission at 615 nm was significantly quenched due to the internal filtration effect (IFE). The fluorescence intensity ratio I₄₃₈/I₆₁₅ shows a good linear relationship with DPA concentration in the range of 0.5–60 μM, and the detection limit is as low as 0.36 μM. This method provides a sensitive and reliable alternative strategy for rapid DPA monitoring.