A Novel Fluorescence Aptasensor Based on Magnetic Beads/Gold Nanoparticles/DNA-Stabilized Silver Nanoclusters for Detection of Salmonella Typhimurium

Abstract

<i>Salmonella</i> Typhimurium (<i>S.</i> Typhimurium) is a globally distributed foodborne pathogen, which can lead to outbreaks of foodborne infectious diseases. It is essential to guarantee food safety by timely and correct detection of <i>S.</i> Typhimurium. In this investigation, an original fluorescence aptasensor was constructed to detect <i>S.</i> Typhimurium rapidly and sensitively. Through the coupling of magnetic beads, aptamer, and gold nanoparticles (AuNPs), a fluorescence quenching system with a "sandwich structure" was established. The aptamer acted as a link, and its specific binding to <i>S.</i> Typhimurium could release AuNPs from the system. Meanwhile, fluorescent DNA-stabilized silver nanoclusters (DNA-AgNCs) were synthesized. The fluorescence intensity changes caused by the fluorescence resonance energy transfer between DNA-AgNCs and AuNPs were utilized to detect <i>S.</i> Typhimurium. The purposed aptasensor exhibited high selectivity and sensitivity with a linear response to <i>S.</i> Typhimurium, ranging from 3.7 × 10² to 3.7 × 10⁵ cfu/mL. The limit of detection (LOD) was estimated to be 98 cfu/mL within 2 h 10 min. In addition, this method showed excellent application for detection of <i>S.</i> Typhimurium in artificially contaminated milk, with LOD reaching 3.4 × 10² cfu/mL. Therefore, the developed fluorescence aptasensor has great potential to identify <i>S.</i> Typhimurium in foodstuffs.