On the mechanism of eukaryotic cell penetration by α- and β-oligoarginines--targeting infected erythrocytes.

Fluorescein-labeled α- and β-octaarginine amides were synthesized. The route, by which these oligoarginine (OA) derivatives enter cells (hepatocytes, fibroblasts, macrophages), was investigated by confocal fluorescence microscopy. Comparisons (by co-localization experiments) with compounds of known penetration modes revealed that the β-octaarginine amide also uses multiple pathways to enter cells. There was no difference between the α- and the β-OAs. Like other cell-penetrating peptides (CPPs), the β-octaarginine eventually winds up in the nucleoli of the cell nuclei (cf. Chem. Biodiversity, 2004, 1, 65). Surprisingly, there was no entry of α- or β-OA into intact and healthy human erythrocytes (which do not possess a nucleus). Blood cells infected by Plasmodium falciparum (malaria parasite) were, however, entered readily, and the OAs went all the way through a couple of membranes into the parasite. The potential of these results for delivering specific antimalarial drugs directly into the parasite is discussed.