A Low-Field Magnetic Resonance Imaging Aptasensor for the Rapid and Visual Sensing of Pseudomonas aeruginosa in Food, Juice, and Water.

ABSTRACT

In this work, we present a low-field magnetic resonance imaging (LF-MRI) aptasensor based on the difference in magnetic behavior of two magnetic nanoparticles with diameters of 10 (MN10) and 400 nm (MN400) for the rapid detection of Pseudomonas aeruginosa (P. aeruginosa). First, specific anti-P. aeruginosa aptamers were covalently immobilized onto magnetic nanoparticles via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide chemistry for the capture of the target bacteria. In the presence of P. aeruginosa, an MN10-bacteria-MN400 (MBM) complex was formed after binding between the aptamers on magnetic nanoparticles and P. aeruginosa cells. When a magnetic field was applied, the MBM complex and free MN400 were rapidly magnetically separated, and free MN10 left in the solution worked as a T2 (transverse relaxation time) single readout in MRI measurement. Under optimum conditions, the LF-MRI platform provides both image analysis and quantitative detection of P. aeruginosa, with a detection limit of 100 cfu/mL. The feasibility and specificity of the aptasensor were demonstrated in detecting real food, orange juice, and drinking water samples and validated using plate counting methods.