For the sandwich immunoassay of the model analytes, as expected, the sandwich immunoassays based on the 7A3-17B3 pair provided significantly dose-dependent signals for all model analytes (Fig. and Table ). These results also showed that the sensitivities of both competitive and sandwich immunoassays for model analytes are dependent on the length of the molecule. Therefore, an appropriate molecule length may be beneficial to achieving high sensitivity. Both competitive and sandwich immunoassays for MN1-MN4 with short epitope distances of ~6.3 Å showed low sensitivity, with competitive immunoassays being more susceptive to the short epitope distance of the analyte (Fig. and Table ). Only weak signals were detected for MN1-MN4 in sandwich immunoassay even with high concentrations of the analyte (100 µM).