Hierarchical molybdenum disulfide nanosheets based lateral flow immunoassay for highly sensitive detection of tetracycline in food samples

In this study, we report a simple approach for synthesizing three kinds of molybdenum disulfide (MoS2) nanosheets with different sizes of large, middle, and small (which are defined as L-MoS2, M-MoS2 and S-MoS2) by an aqueous-phase exfoliation and differential-zone centrifugation (AE-DC) strategy, and for the first time explored the MoS2 labeled antibodies (Abs) as probes for sensitive detection of tetracycline (TET) on lateral flow assays (LFAs). The hierarchical MoS2 had uniform sizes (Average size: 366 +/- 65.70 nm, 131 +/- 24.39 nm and 55 +/- 8.56 nm for L-MoS2, M-MoS2, and S-MoS2, respectively; thickness: 3 nm, 1 nm for and 0.5 nm for L-MoS2, M-MoS2 and S-MoS2, respectively), and all exhibited excellent water-dispersibility and stability. Compared with M-MoS2 and S-MoS2 based LFAs, L-MoS2 based LFA particularly displayed highly sensitive detection of TET due to the larger surface area and stronger color intensity. Under optimized experimental conditions, the developed L-MoS2-based immunosensor showed a great linear relationship over the range of 0.012-0.75 ng/mL in 15 min and a signal sensitivity up to 0.023 ng/mL for TET detection, which was at least 17-fold lower than traditional gold nanoparticles based LFA. The assay resulted in excellent specificity and reproducibility, and can be well-applied in milk, honey, and beef samples for monitoring TET.