Rapid detection of probiotics in aquaculture using a fluorescent ligand sensor based on a Zr-MOF@Methylene blue composite

We constructed a novel fluorescent aptasensor based on Zr-MOF@MB composite material for rapid and highly sensitive detection of probiotics Bacillus subtilis and Lactobacillus acidophilus in shrimp aquaculture. The sensor utilizes a zirconium-based metal–organic framework to load the signal molecule methylene blue (MB) and immobilizes specific aptamers via Zr–O–P bonds to form a gating structure. In the presence of the target bacteria, a conformational change in the aptamer triggers the release of MB, leading to a decrease in fluorescence intensity, thereby enabling quantitative determination of the bacteria. The method completes detection within 30 min, with a linear range of 10¹ to 10⁷ CFU/mL and detection limit of 7 CFU/mL for B. subtilis and 10 CFU/mL for L. acidophilus . The developed sensor is simple to operate and highly sensitive, providing a reliable tool for effective monitoring of probiotics in shrimp aquaculture and offering new insights for the development of aptamer-based sensors for microbial detection in complex matrices.