AFP and hepatocellular carcinoma: Figure 3 reveals that a distinctive signal was only observed by adding LCN2, not controls (A to D), nonspecific proteins (BSA, GST and HSA) or potential HCC biomarkers (AFP). This implies that the aptamer-based sandwich assay was responsible for the significant and specific binding to LCN2. In agreement with the dot blotting (Fig. 2) and SPR data (Supporting InformationFigure S4), the capture and reporter aptamers did not react with each other (Fig. 3, C in upper control box).