Gold nanoparticle-based enhanced lateral flow immunoassay for detection of Cronobacter sakazakii in powdered infant formula

Cronobacter sakazakii is an opportunistic foodborne pathogen that can infect newborns through powdered infant formula (PIF). In this study, we developed a novel enhanced lateral flow immunoassay (LFA) with enhanced sensitivity for detection of C. sakazakii in PIF by the naked eye. The proposed strategy for signal enhancement of the traditional LFA used concentrated gold nanoparticles (AuNP) as the enhancer to conjugate with capture antibodies, which could increase the immobilized capture antibodies concentration at the detection zone to improve capture efficiency. Besides, the detection signal was further amplified by accumulated AuNP as the C. sakazakii labeled with AuNP probes was captured by antibodies conjugated with enhancer at the test line. We also studied the effect of different concentrations of capture antibodies and concentrated AuNP on detection performance, and found that 2.2 mg/mL of capture antibodies and 0.06 nM concentrated AuNP were the optimal combination that could avoid a false-positive signal and maximally amplify the detection signal of the enhanced LFA. Using this strategy, the detection sensitivity of the enhanced LFA was 103 cfu/mL and improved 100-fold compared with traditional LFA. The strip was highly specific to C. sakazakii, and the time for detection of C. sakazakii in PIF was shortened by 3 h. In summary, the enhanced LFA developed by the addition of concentrated AuNP as the enhancer can be used as a sensitive, rapid, visual qualitative and point-of-care test method for detecting target analytes.