Ultrasensitive label-free immunochromatographic strip sensor for Salmonella determination based on salt-induced aggregated gold nanoparticles

Here we present an innovative label-free immunochromatographic strip (ICTS) sensor, in which salt-induced aggregated gold nanoparticles (SIA-AuNPs) act as the signal probe, allowing in 14 min the identification and sensitive quantification of Salmonella as model targets. It has been evidenced that SIA-AuNPs could be absorbed on the surface of bacteria based on van der Waals forces. The SIA-AuNPs@Salmonella complex was captured by anti -Salmonella polyclonal antibody deposited on the test zone. With the label-free ICTS sensor, we successfully detected Salmonella in a concentration range of 10(3)-10(8) CFU/mL and a visual detection limit of 1 x 10(3) CFU/mL. The band of test zone could be distinguished at a concentration of 10(3) CFU/mL by naked eye, which is 100-fold lower than the cationic AuNPs based method. The strip sensor was further validated with real samples including cabbage and drinking water with excellent precision and showed to provide excellent recovery.

Automated summary

The innovative label-free ICTS sensor utilizes salt-induced aggregated gold nanoparticles as the signal probe for rapid identification of Salmonella, with the ability to show color difference even at low concentrations, providing excellent precision and recovery rates in real samples.