Fluorescent aptasensor for detection of Salmonella typhimurium using boric acid-functionalized terbium metal–organic framework and magnetic nanoparticles

A fluorescent detection platform was designed using boric acid-functionalized terbium metal–organic framework (BA-Tb-MOF) and carboxyl-modified magnetic nanoparticles (MNPs) to identify Salmonella typhimurium (S. typhimurium) bacteria. Firstly, carboxyl-modified Fe₃O₄MNPs were coated with specific aptamer (Apt-MNPs) as the capture probe for S. typhimurium. Then, the Apt-MNPs were added to the bacterial suspension to facilitate the targeted binding. Subsequently, the fluorescent probe (BA-Tb-MOF) was introduced into this solution. The BA-Tb-MOF was strongly attached to the bacterial surface through interactions between BA and glycolipids on the bacterial cell walls, forming a stable complex. As the bacterial concentration increased, the fluorescence intensity of the solution progressively decreased due to the binding and removal of bacteria-Apt-MNPs/BA-Tb-MOF complexes through magnetic separation. Under optimum conditions, the concentration of S. typhimurium and the fluorescence intensity showed an inverse linear relationship within the range of 10¹–10⁹ CFU/mL, and the detection limit was 4 CFU/mL. The developed sensor showed high specificity against several other pathogenic bacteria such as E. coli, S. aureus, and P. aeruginosa. The developed fluorescence platform also successfully detected the S. typhimurium in drinking water and egg samples with satisfactory recoveries (83–98%). This strategy can be investigated further for the detection of S. typhimurium and other pathogens in food and clinical samples.

Graphical Abstract