Portable dual-mode biosensor based on smartphone and glucometer for on-site sensitive detection of Listeria monocytogenes

Contamination of Listeria monocytogenes (L. monocytogenes) in the environment and food can pose a serious threat to human health, and there is an urgent need to establish sensitive on-situ detection methods to mitigate its hazards. In this study, we have developed a field assay that combines magnetic separation technology with antibody-labeled ZIF-8 encapsulating glucose oxidase (GOD@ZIF-8@Ab) to capture and specifically identify L. monocytogenes while GOD catalyzes glucose catabolism to produce signal changes in glucometers. On the other side, horseradish peroxidase (HRP) and 3,3',5,5'-tetramethylbenzidine (TMB) were added to recombined with the H₂O₂ generated by the catalyst to form a colorimetric reaction system that changes from colorless to blue. The smartphone software was used for RGB analysis to complete the on-site colorimetric detection of L. monocytogenes. This dual-mode biosensor showed good detection performance for the on-site application of L. monocytogenes in lake water and juice samples, both with a limit of detection up to 10¹ CFU/mL and a good linear range of 10¹-10⁶ CFU/mL. Therefore, this dual-mode on-site detection biosensor has a promising application for the early screening of L. monocytogenes in environmental and food samples.