TFRC and neoplasm: The further saturation binding curve and Scatchard analysis demonstrate that the Kd value for Gd-HFn binding to MDA-MB-231 tumor cells is 55.8 nM and the total binding capacity Bmax is 39.4 × 10-19 mol/cell (Figure 3B), showing that Gd-HFn has a high binding affinity and capacity for TfR1-positive tumor cells.