To further explore the specificity of Trast-NGs, we compared the extent of growth inhibition (MTT dye incorporation) of ErbB2-overexpressing (BT-474) vs. ErbB2-low (MCF-7) breast cancer cell lines by DOX encapsulated within control IgG-NGs vs. Trast-NG (Table S1). Here, ERBB2 is linked to breast carcinoma.