Fluorescent aptasensor for enrofloxacin detection based on APE1-assisted amplification and CsPbBr₃@MSN nanocomposites

In this work, a fluorescent aptasensor was constructed for enrofloxacin (ENR) detection by combining the polyvalent aptamer (PA) structure, apurinic/apyrimidinic endonuclease 1 (APE1)-mediated signal amplification and mesoporous silica-encapsulated perovskite quantum dot (CsPbBr₃@MSN) nanocomposites. With their multiple recognition sites, polyvalent aptamers bonded to ENR and released the trigger for the strand displacement reaction. Meanwhile, a highly sensitive FRET-based sensor was constructed using the CsPbBr₃@MSN probe and gold nanoparticles (Au NPs). In the presence of the trigger and APE1, the fluorescence was recovered by separating the CsPbBr₃@MSN probe and Au NPs via a cyclic strand displacement reaction. Coupled with the signal amplification strategy, this system achieved the linear detection of ENR in the range of 0.1 pg mL^-1 to 50 ng mL^-1 with a detection limit of 0.073 pg mL^-1. This sensor offers a novel analytical strategy for detecting antibiotic residues and holds significant potential for applications in food safety monitoring and environmental analysis.