Phage-functionalized Ce-UiO-66-NH₂ nanozyme colorimetric biosensor for ultrasensitive detection and quantification of viable E. coli in food matrices.

A phage HH3-functionalized Ce-UiO-66-NH₂ nanozyme-based colorimetric biosensor was developed for the quantification of viable Escherichia coli (E. coli), overcoming the drawbacks of slow detection and inadequate live/dead bacterial discrimination in conventional analytical methods. The proposed platform achieves target detection within 35 min, with a low limit of detection (LOD) of 3.2 CFU/mL and satisfactory spiked recoveries ranging from 82.75% to 122.06%. Mechanistically, Ce-UiO-66-NH₂ exhibits intrinsic oxidase-like activity that directly catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to blue-colored oxTMB. The color intensity of this chromogenic reaction is positively correlated with E. coli concentration, enabling quantitative analysis. Benefiting from the specific recognition capability of phage HH3, the biosensor shows negligible responses to non-host bacteria and heat-inactivated E. coli. This distinctive advantage cannot be achieved by antibody- or PCR-based strategies. This nanozyme-phage platform outperforms most reported sensors and possesses promising potential for rapid and selective quantification of viable E. coli in complex food and environmental matrices.