Cell penetration and cell-selective drug delivery using α-helix peptides conjugated with gold nanoparticles.

Cell penetrating peptides (CPPs) have been developed as vectors for molecular delivery into various cells for use in drug delivery, gene therapy and cancer treatment by their property transporting various molecules into cytoplasm. CPPs with high internalization, cell specificity, and low cytotoxicity have been considered to increase the applicability for cell engineering. Gold nanospheres (GNSs) are a useful tool for molecular imaging, because they are non-cytotoxic and have high solubility, ease of synthesis and excellent light scattering property. Here, we investigated the cell penetrability using α-helix peptides of 17-amino acids conjugated to gold nanospheres (P-GNS). Depending on the peptide sequence had the different cell penetrating (CP) activity for three kinds of cell lines. P-GNS showed low cytotoxicity and high selectivity against three cell types, despite just one amino acid difference between the peptide. We studied the cytotoxic activity of an anti-cancer drug doxorubicin (DOX) conjugated to the P-GNS. They showed different cytotoxicity against the three cell lines, depending on the peptide sequence, with a higher efficiency than free DOX at the same concentration. The cytotoxicity by DOX was correlated with the CP activity of the peptides against the three cell lines. These results demonstrated that P-GNS would be a useful tool for the development of a new cell-selective drug delivery system.