Determination of Escherichia coli O157:H7 Using a Flower-like Concanavalin A Copper (II) Phosphate Nanocomposite as a Probe for Lateral Flow Biosensing

Abstract

A novel lateral flow biosensor using flower-like concanavalin A (Con A)-Cu3(PO4)2 organic − inorganic nanocomposites for a signal probe was developed for the visual detection of Escherichia coli O157:H7 with high sensitivity and low cost. These nanocomposites, combining signal amplification and biological recognition, were composed of Con A, fluorescein isothiocyanate (FITC), biotin, and Cu3(PO4)2. The sandwich system of magnetic bead − conjugated antibody/Escherichia coli O157:H7/ConA-Cu3(PO4)2 organic − inorganic nanocomposites was fabricated using magnetic separation. The magnetically separated organic − inorganic nanocomposites were visually detected with a lateral flow biosensor. The nanocomposites introduced numerous gold nanoparticles (AuNPs) on the lateral flow biosensor via special recognition between streptavidin immobilized on AuNPs and biotin of nanocomposites. The nanocomposites were subsequently grabbed on the test line by specific reactions between the anti-FITC monoclonal antibody on the test line and FITC on organic − inorganic nanocomposites. The assembly of AuNPs on the biosensor test line activated the visual detection of the target bacteria. Under optimized conditions, the quantitative detection of E. coli O157:H7 was performed in the 10 to 105 CFU/mL linear range with a detection limit of 10 CFU/mL. This visual detection system is an efficient, stable, and nontoxic nanocomposite tag for detecting pathogens in food.