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 × 10 5  CFU/mL and 2.85 × 10 5  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.