Development of a Two-stage Label-free Aptasensing Platform for Rapid Detection of Cronobacter sakazakii in Powdered Infant Formula

Introduction: Cronobacter sakazakii constitutes one of the most life-threatening foodborne pathogens in neonates, and is largely attributed to its presence in powdered infant formula. Despite the high risk of infection of Cronobacter spp., including C. sakazakii, most studies on the development of a Cronobacter-specific biosensor have been performed using self-developed antibodies, because there is currently no commercial antibody available against this bacterium.

Purpose: In this study, a sensitive and convenient two-stage label-free aptasensing platform was developed for colorimetric detection of C. sakazakii in powdered infant formula.

Methods: We selected aptamers against live intact C. sakazakii cells using the whole-cell SELEX, and then established a two-stage aptasensing platform using aptasensors based on the unmodified selected aptamers and gold nanoparticles for specific detection of C. sakazakii in realistic samples. The analytical performance of the developed platform was evaluated with artificially inoculated powdered infant formula.

Results: Under the optimum conditions determined in the experiments, C. sakazakii in powdered infant formula could be detected with the naked eye within 30 min at a concentration as low as 7.1 × 10³ CFU/ml, and the linear range was from 7.1 × 10³ to 7.1 × 10⁷ CFU/ml.

Significance: To our knowledge, this is the first report of an aptamer against C. sakazakii, and of a label-free aptasensor to detect foodborne pathogens in food items. Finally, the platform may be customized with target-specific aptamers to detect other bacteria of interest.