A paper-tip dual-mode aptasensor integrating SERS and colorimetric method for detecting oxytetracycline

Oxytetracycline (OTC) is widely used in aquaculture and livestock farming, and its leaching into the environment and residues in food can easily lead to bioaccumulation risks. There is an urgent need to develop a simple and efficient method for detecting OTC. Herein, we developed a novel paper-tip dual-mode aptasensor for rapid and high-sensitivity detection of OTC. Firstly, a novel composite probe was designed by co-modifying 4MBA and horseradish peroxidase (HRP) on the silver nanoparticles (AgNPs), which owns the Raman "hotspot" effect and the catalytic activity of peroxidase. Then, we utilized the lateral flow on the paper tip to achieve the target capture and probe enrichment within 1 h, simplifying the experimental operation and ensuring detection stability. The paper-tip aptasensor could provide Raman and colorimetric signals that effectively addressed the false-positive issues and low accuracy commonly observed in traditional paper-based sensors. The paper-tip aptasensor displayed a wide linear detection range for the detection of OTC (1-10,000 nM) with low detection limit of 0.635 nM (Raman) and 0.728 nM (colorimetric). The recovery of OTC in spiked real samples ranged from 81.05% to 111.60% (n = 3), which indicated the good applicability of the paper-tip aptasensor. The paper-tip aptasensor has the advantages of simple operation, low cost, portability and high sensitivity, which is anticipated to serve as a powerful alternative for rapid, on-site antibiotic detection.