Cell-penetrating peptides (CPPs) have the ability to efficiently internalize into cells and thus have been used as a vector for the intracellular delivery of various bioactive molecules. The introduction of a hydrophobic core to CPPs may increase their interaction with membranes and facilitate their translocation into cells. While the usefulness of acylated oligoarginine to gene and siRNA delivery has been largely reported, little information is available about their use for the delivery of small molecular-weight compounds, peptides and proteins. In this report, we employed octaarginine (R8) as a typical arginine-rich CPP and evaluated the effect of acylation using butanoic, hexanoic and decanoic acids on its capacity as a delivery vector. Hexanoyl octaarginine (C6R8-Alexa) showed the highest efficiency of cellular uptake of the studied variants, ten times higher than R8-Alexa. C6R8-Alexa also produced a diffuse cytosolic distribution. On the other hand, a less significant effect of C6R8 over R8 was observed for the delivery of proteins, suggesting that the advantage of C6R8 may be obtained during the delivery of relatively small molecular-weight compounds. Although less prominent than at 37°C, a significant cytosolic distribution of C6R8-Alexa was observed at 4°C, and this suggested the potential ability of the C6R8 peptide for direct penetration through plasma membranes.
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