It is of interest to note that the inhibition effect of TfR1 antibody and mannose receptor 1 antibody on the uptake of the protein units was less significant under an environmental pH of 7.4, which could be explained that the majority of the targeting moieties in the cross-linked protein units were still in a caged state and therefore their uptake by DCs or tumor cells was less affected when disabling the specific ligand-receptor binding. Here, TFRC is linked to neoplasm.