“…9 It must be noted that at the concentration corresponding to the LOD, there is a relatively high surplus of PSA molecules over MBs. Considering the binding capacity, size, and weight of a single MB, 43,44 each MB can bind approximately 6.0 × 10 4 to 7.8 × 10 4 antibody molecules. Therefore, with 50 μg mL −1 of MBs and a PSA concentration of 1.04 pg mL −1 , there are approximately 400 PSA molecules per MB, which corresponds to a fractional antibody occupancy of 0.5-0.7%.…”