Fully Integrated Microfluidic Biosensor with Finger Actuation for the Ultrasensitive Detection of <i>Escherichia coli</i> O157:H7

Abstract

A portable microfluidic biosensor was developed for the detection of <i>E. coli</i> O157:H7 using finger actuation. The chip was assembled with three functional zones, immunomagnetic separation, nucleic acid extraction and purification, and signal detection. First, antibody-modified magnetic nanoparticles (MNPs) were used to separate the target bacteria from the sample. The captured bacteria were then lysed and silica-coated MNPs were used to absorb DNA, followed by washing and eluting to obtain purified DNA. The obtained DNA was subjected to amplification and fluorescence detection based on the recombinase polymerase amplification-clustered regularly interspaced short palindromic repeat-associated protein/Cas12a reaction. The fluorescence images were collected and analyzed using a smartphone app under a 3D-printed detection device. It could quantitatively detect <i>E. coli</i> O157:H7 from 10² to 10⁸ CFU/mL in 2.5 h with a limit of detection (LOD) of 10 CFU/mL. The recovery rate ranged from 104 to 120%. Overall, the biosensor realizes "sample-in and answer-out" assay for <i>E. coli</i> O157:H7 and eliminates the need for external pumps and skilled personnel.