An aptamer-based fluorescence probe for facile detection of lipopolysaccharide in drinks

Abstract

Bacterial toxin contamination is a serious food safety issue. Rapid, facile detection of bacterial toxins in food is crucial to control their harmful effects on human health. In this study, a facile, selective, and cost-effective method with a 6-carboxy-X-rhodamine labeled lipopolysaccharide binding aptamer (ROX-LBA)/GO fluorescent probe was developed based on the specific recognition characteristics of aptamers and the super fluorescence quenching efficiency of graphene oxide (GO) and used for the detection of lipopolysaccharides (LPS). ROX-LBA is adsorbed on the GO surface because of its strong π–π stacking interactions in the flexible single-stranded state, and fluorescence is quenched by GO via Förster resonance energy transfer (FRET). After adding LPS, the aptamer binds to LPS and forms a LPS/ROX-LBA complex, which exhibits weak binding affinity with GO. ROX-LBA cannot effectively combine with GO, and fluorescence is restored. The concentration of LPS can be quantitatively analyzed by observing fluorescence changes in the sensing system. The fluorescence intensity proportionally increases with LPS concentration (25–1600 ng mL⁻¹), and the detection limit is 15.7 ng mL⁻¹. Hence, the proposed method provides an alternative strategy for the specific detection of endotoxin in drink samples (e.g., apple juice and beer) and could be widely applied to quantify various bacterial toxins by replacing the aptamer sequences.