Ultrasensitive detection assay for Cronobacter sakazakii based on nucleic acid-driven aggregation-induced emission of gold nanoclusters and cascaded signal amplification

Cronobacter sakazakii (C. sakazakii), a foodborne pathogen frequently present in contaminated powdered infant formula (PIF), poses a substantial threat to food safety. Herein, a novel fluorescent biosensor based on gold nanoclusters (AuNCs) that exhibit aggregation-induced emission (AIE) when triggered by nucleic acids was developed. This biosensor integrates the exponential amplification reaction (EXPAR) with hybridization chain reaction (HCR) signal amplification (EXHCR), enabling ultrasensitive detection of C. sakazakii. The aggregations of glutathione protected AuNCs assembled by G-rich sequences (HP1, and HP2) was affected by the EXHCR reaction initiated with C. sakazakii, forming G-quadruplex nanowires, leading to the dis-aggregation of AuNCs and a turn-off response of fluorescence, thereby realizing the detection of C. sakazakii. The changes are discernible on cellulose paper with the naked eyes. The biosensor demonstrates exceptional selectivity due to the integration of an aptamer and a dual signal amplification strategy. Under optimized conditions, it achieves a remarkable detection limit of 1.10×100 CFU/mL, and a broad linear range from 1.10×100 to 1.10×107 CFU/mL. Furthermore, the biosensor's capability to identify C. sakazakii in artificially contaminated milk powder with recoveries ranging from 97.8% to 107%, underscores its reliability and accuracy. Overall, this study offers a promising approach for nucleic acid and AIE-based detection, exhibiting considerable potential for developing highly efficient bacterial detectors.