A dual-mode aptasensor based on freeze-thaw induced aggregation of gold nanoparticles and FRET for Staphylococcus aureus detection

The foodborne pathogen Staphylococcus aureus (S. aureus), known for its high virulence, presents a substantial risk to food safety. In this study, we proposed a detection platform utilizing the aptamer-induced aggregation of gold nanoparticles (AuNPs) through freeze-thaw and the fluorescence resonance energy transfer (FRET) between FITC and AuNPs. This platform offered an efficient means of identifying S. aureus. The thiolated aptamer exhibited specific binding affinity towards S. aureus, whereas AuNPs with the unbound aptamer underwent varying degrees of aggregation following freeze-thaw, leading to distinct alterations in color. After the aggregation of AuNPs, FRET between AuNPs and FITC diminished, followed by a gradual restoration of fluorescence. Under optimal experimental conditions, the colorimetric mode exhibited a detection limit of 5 CFU/mL for S. aureus, while the fluorescence mode demonstrated a detection limit of 2 CFU/mL. The validity of the developed method was confirmed through the plate counting method, with no significant disparities observed in the obtained results. Compared to the plate culture method, the proposed dual-mode strategy can be completed within 95 min, greatly shortening the detection time. Consequently, this method holds promising potential for the rapid and sensitive analysis of S. aureus.