Sensitive and hook effect–free lateral flow assay integrated with cascade signal transduction system

Abstract

The traditional lateral flow immunoassay (LFI) for detecting foodborne pathogens suffers from low sensitivity and hook effect that led false–negative result. Here, we established a novel LFI integrated with a cascade signal transduction system for the sensitive and hook effect–free detection of Escherichia coli O157:H7 (E. coli O157:H7). First, E. coli O157:H7 was captured by immunomagnetic nanoparticles (IMNPs) and monoclonal antibody–β–lactamase–gold nanoparticles (ILAuNPs) forming sandwich complexes. Second, penicillin solution was added and hydrolyzed by β–lactamase on the sandwich complexes. Last, the penicillin hydrolysate was transferred to an ultrasensitive penicillin immunochromatographic test strip (PIST). With the high β–lactamase activity of ILAuNPs (0.1 μL of ILAuNPs hydrolyzing 20 ng/mL of penicillin) and ultrasensitive PIST (cutoff value achieving 2 ng/mL), the detection sensitivity of this method was 1.37 × 102 CFU/mL for E. coli O157:H7, which prevailed 1000 times over that of the traditional LFI. This work also efficiently solved hook effect when the E. coli O157:H7 concentration was over 107 CFU/mL. Thus, the detection range of the novel method was 102–108 CFU/mL, thereby expanding by four orders of magnitude than that of the traditional LFI (105–107 CFU/mL).