A novel microfluidic colorimetric biosensor for rapid and automatic detection Escherichia coli O157:H7 in aquaponics water

The on-site and real-time detection of pathogenic bacteria under the aquaponics production process is critical for controlling diseases of aquatic products and ensuring food safety of agricultural products. In this study, a novel microfluidic colorimetric biosensor was developed for rapid, sensitive and automated detection of the widespread foodborne and waterborne pathogen, Escherichia coli O157:H7 ( E. coli O157:H7). Firstly, immune magnetic nanoparticles (MNPs), samples and immune platinum nanoparticles (Pt NPs) were mixed and incubated in “pearl chain” micromixers forming MNP-bacteria-Pt NP sandwich complexes. Then, a mixture of 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H 2 O 2 ) was injected and catalyzed by Pt NPs to produce blue oxidized TMB (oxTMB). Finally, colorimetric analysis of the catalytic substrate was performed to determine the target bacterial concentration using an improved AS7265x spectral sensor. As shown in the experimental results, this biosensor was able to detect E. coli O157:H7 at 5 × 10 1  ∼ 5 × 10 6 CFU/mL within 45 min with the lower detection limit of 17 CFU/mL. Notably, the biosensor is a universal detection platform that allows for the detection of other pathogenic bacteria in aquaponics water via the replacement of the biometric element.