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

<i>Listeria monocytogenes</i>, 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 <i>L. monocytogenes</i>-specific aptamer with cDNA attached to carboxyl magnetic beads (Apt-cDNA-CMBs). In the presence of <i>L. monocytogenes</i>, 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. <i>monocytogenes</i>, 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 <i>L. monocytogenes.</i>