Synthesis, characterization and application of gold nanoparticles capped by RGD fuctionalised peptides

Biocompatible gold nanoparticles (AuNPs), stabilised by RGD-(GC)2 and (GC)2 peptides, were obtained by reduction of tetrachloroaurate aqueous solutions. RGD-(GC)2 peptide encompasses a RGD motif, chosen as a targeting ligand for αvß3 integrin receptor generally recognised to be a tumor and angiogenesis marker and a GC motif to stabilise the gold nanoparticles. The peptides were prepared ad hoc by Fmoc synthesis. The colloidal systems have been characterised by UV-visible, ATR-FTIR, mono and bidimensional NMR techniques and Confocal and TEM microscopies. The cellular uptake of Au@RGD-(GC)2 and Au@(GC)2 gold particles into U87 cells (human glioblastoma cell), were investigated by confocal microscopy. A quantitative determination of the uptaken nanoparticles has been carried out by measuring the brightness of the images of both systems that highlighted the importance of the RGD termination of the peptide. In order to understand if the receptor-mediated entrance could be favourite, TEM experiments with Au@RGD-(GC)2 and Au@(GC)2 nanoparticles were carried out. Only Au@RGD-(GC)2 nanoparticles were accumulated in the cells. Further phenomena occurred inside the cell as we observed Au NPs free in the cytosol, in the nucleus and nucleolus.