A gravity-driven microfluidic platform integrating Fe-N-C nanozyme-enhanced immunoassay for power-free detection of...

Bacterial screening is an important measure to ensure food safety. In this study, a gravity-driven microfluidic platform was newly developed for POCT of pathogens by integrating magnetic immunocapture, nanozymatic signal amplification, and gravity-driven fluidic control. First, magnetic beads, bacteria and nanozymes were reacted to form bead-bacteria-nanozyme conjugates. After the conjugates were captured against the magnet and washed with washing buffer, they were then used to catalyze substrate to blue product. Finally, the images of product were collected and measured to determine bacterial concentration. All bacterial detection procedures from sample loading to colorimetric determination were sequentially conducted in the microfluidic chip through gravity-driven control of reagents to achieve designated reactions in designated chambers at designated time. This power-free platform was capable of detecting Salmonella from 7.4 × 10¹ to 7.4 × 10⁶ CFU/mL with a detection limit of 7 CFU/200 μL and the procedure from sample loading to colorimetric determination was completed in 30 min.