Green synthesis of salt-tolerant gold nanoparticles for the rapid qualitative detection of Listeria monocytogenes in lateral flow immunoassay

Gold nanoparticles (AuNPs)-based lateral flow immunoassay (LFIA) is a widely used detection technique. Here, we developed a novel method for green synthesis of a salt-tolerant AuNPs by using aqueous extract of Damask rose petals (AEDR), for the application of Listeria monocytogenes (L. monocytogenes) detection by LFIA. Key parameters were optimized to achieve an improved optical LFIA performance, and the detection limit and specificity were further studied. AEDR-AuNPs were synthesized within 1 min at RT by AEDR at a concentration of 240 µg/mL, and the method was rapid, simple, economical and environmentally friendly. The AEDR-AuNPs were spherical with the size mainly ranging from 20 to 28 nm, and the salt stability was determined to be 0.4 M NaCl, which is 10 times higher than AuNPs synthesized by citrate reducing method. The optimized immunization concentration of anti-Listeria monocytogenes polyclonal antibody to AEDR-AuNPs was 60 µg/mL. The optimized antibody concentrations of test (T) line and control (C) line were determined as 1 mg/mL and 0.5 mg/mL, respectively. The detection limit was 2.5 × 105 CFU/mL and 2.85 × 105 CFU/mL in pure L. monocytogenes culture and pork tenderloin sample, respectively, and the result can be read by naked eye within 10 min. The antibody–AEDR-AuNPs LFIA strip showed no cross-reaction with all the tested bacteria including Staphylococcus aureus, Pseudomonas aeruginosa, Vibrio parahaemolyticus, Bacillus subtilis, Escherichia coli O157:H7 and Salmonella typhimurium. This approach showed a promising application for the detection of L. monocytogenes concerning food safety.