A colorimetric/fluorescent dual-mode aptasensor for the rapid and sensitive detection of Listeria monocytogenes.

Listeria monocytogenes, a major foodborne pathogen, causes a serious infection. Therefore, better detection methods are needed to prevent outbreaks. Herein, a colorimetric/fluorescent dual-mode aptasensor using (GlcN)(5), AuNPs, and QD-(COOH) was developed for its rapid detection. The probe was an L. monocytogenes-specific aptamer with cDNA attached to carboxyl magnetic beads (Apt-cDNA-CMBs). In the presence of L. monocytogenes, the aptamer binds to it, making cDNA detach and adsorb onto AuNPs, inhibiting (GlcN)(5)-induced aggregation and keeping the AuNPs solution red. Meanwhile, dispersed AuNPs quench QDs, leading to reduced fluorescence. Without L. monocytogenes, AuNPs aggregate, turning the solution blue, and QD fluorescence remains unchanged. The lowest detection limits (LODs) were 4.21 CFU/mL (colorimetry) and 8.89 CFU/mL (fluorescence). The aptasensor showed excellent recoveries in beef (85.11%-107.53%) and salmon (86.21%-109.98%). This dual-mode aptasensor offered a promising solution for simple, rapid, and reliable on-site detection of L. monocytogenes.