A One-Step Colorimetric/Fluorescent Dual-Mode Aptasensor for the Detection of Listeria monocytogenes

Abstract

Listeria monocytogenes is one of the most important foodborne pathogens that can cause infectious diseases and food poisoning. Herein, a colorimetric/fluorescent dual-mode aptasensor based on (GlcN)5, AuNPs and QD-COOH was developed for rapid detection of L.monocytogenes. The complementary double strand formed by L.monocytogenes-specific aptamer and cDNA attached on carboxyl magnetic beads (Apt-cDNA-CMBs) served as the detection probe. In the presence of L.monocytogenes, the aptamer binds to it, causing the cDNA to detach from CMBs and adsorb on the surface of AuNPs, inhibiting the aggregation of AuNPs induced by (GlcN)5. Thereby, the solution of AuNPs remains red. Meanwhile, dispersed AuNPs could quench QDs, leading to significant decreases of fluorescence intensity. However, when L.monocytogenes is absent, the solution of AuNPs turns blue due to the deprotected effect of cDNA while the fluorescence intensity of QDs remains unchanged. This sensor shows good sensitivity and selectivity, with the lowest detection limit (LOD) of 4.36 CFU/mL for colorimetry and 7.65 CFU/mL for fluorescence. Additionally, this sensor can be applied to beef sample detection with excellent recoveries ( 85.27%-119.35%). Hence, this aptasensor can be considered as a promising tool for simple, rapid on-site detection of L.monocytogenes.

Keywords: Listeria monocytogenes, Dual-Mode aptasensor, AuNPs, (GlcN)5, QD-COOH