Additional file 1: Figure S1. UV/Vis spectra of “bare” NPs (Au@tiopronin) before the modification, and peptide, PEG or TAMRA-CAD modified NPs. a) DBP (red line, Au@tiopronin-DynPro), IntCT (cyan line, Au@tiopronin-IntCt) and TAMRA (blue line, Au@tiopronin-IntCt-TAMRA-CAD); b) DBP-PEG (red line, Au@tiopronin-DynPro/PEG), IntCT-PEG (cyan line, Au@tiopronin-IntCt/PEG) and TAMRA-PEG (blue line, Au@tiopronin-IntCt-TAMRA-CAD/PEG). Figure S2. Fluorescence spectra of “bare” NPs (Au@tiopronin) before the modification, and peptide, PEG or TAMRA-CAD modified NPs. a) DBP (red line, Au@tiopronin-DynPro), IntCT (cyan line, Au@tiopronin-IntCt) and TAMRA (blue line, Au@tiopronin-IntCt-TAMRA-CAD); b) DBP-PEG (red line, Au@tiopronin-DynPro/PEG), IntCT-PEG (cyan line, Au@tiopronin-IntCt/PEG) and TAMRA-PEG (blue line, Au@tiopronin-IntCt-TAMRA-CAD/PEG). Figure S3. ζ-potential bar diagram of “bare” NPs (Au@tiopronin) before the modification, and modified peptide or TAMRA-CAD modified NPs: DBP (Au@DynPro), IntCT (Au@IntCt), TAMRA (Au@TAMRA-CAD), DBP-PEG (Au@DynPro/PEG), IntCT-PEG (Au@IntCt/PEG) and TAMRA-PEG (Au@TAMRA-CAD/PEG). Table S1. ζ-potential values of “bare” NPs (Au@tiopronin) before the modification, and peptide, PEG or TAMRA-CAD modified NPs: DBP (Au@DynPro), IntCT (Au@IntCt), TAMRA (Au@TAMRA-CAD), DBP-PEG (Au@DynPro/PEG), IntCT-PEG (Au@IntCt/PEG) and TAMRA-PEG (Au@TAMRA-CAD/PEG). Figure S4. The figure shows the cellular uptake (according to intracellular MFI) of Au@DynPro, Au@DynPro-PEG, compared to nanoparticles modified with internal control peptide (IntCt), Au@IntCt and Au@IntCt-PEG. Mean fluorescence intensity (MFI) of modified NPs after 1 h incubation. Figure S5. This figure shows the absence of cytotoxic effect of the NPs in Vero cells. Cell viability (a) and cell proliferation (b) were analyzed after incubation of cells with increasing concentrations of the different Au@DBP that exceeded those used in this study. A significant decrease in cell counts or cell proliferation was not observed.