A novel colorimetric and fluorescent dual-mode 3D paper-based microfluidic aptasensor for the point-of-care detection of sulfadimethoxine

Sulfadimethoxine antibiotics (SDM) are commonly used in aquatic foods to inhibit bacteria, but their residues in aquatic food pose certain risks to public health. Herein, we developed a systematic portable biosensing platform for SDM, which comprised a dual-mode three-dimensional paper-based microfluidic chip (3D-μPAD), a dual-light portable device, and a smartphone application for obtaining results. The detection principle of the dual-mode 3D-μPAD was based on the aggregation of Ag NPs without the protection of aptamers and the inner filter effect (IFE) between Mg, N-CDs and Ag NPs. With the addition of SDM, the significant change of two signals can be sensitively recognized in the portable device and calculated by a self-developed mini program in the smartphone to obtain the detection results. Under optimal conditions, SDM was sensitively detected in the range of 10-1000 ng/mL with an estimated limit of detection (LOD) of 0.13 ng/mL and 0.21 ng/mL in fluorescence and colorimetric modes, respectively. Moreover, this platform was successfully applied to determine SDM in fish with recoveries of 96.7%-113.6% and 98.2%-105.1%, respectively. This method has the advantages of low detection cost, low reagent consumption, and unlimited instruments and operators, which better fulfills the point-of-care needs of hazards analysis in food.