The cell membrane is composed mainly of phospholipids, which separates cells' interior from the extracellular space. The properties of the cell membrane create a significant obstacle in intracellular cargo delivery. Cell-penetrating peptides (CPPs) have been introduced as a promising drug delivery system that can penetrate the cell membranes. Some of the CPPs can improve the cellular uptake of various cell impermeable compounds. Amphiphilic cyclic peptides containing alternative arginine and tryptophan such as [WR]5 have been shown to enhance the transport of cargo molecules across the cell membrane. Herein, we report the synthesis and biological evaluation of a novel series of hybrid cyclic-linear peptides containing alternative positive and hydrophobic amino acids, namely [(RW)5K]WR, [(RW)5K](WR)2, [(RW)5K](WR)3, [(RW)5K](WR)4, and [(RW)5K](WR)5. The peptides were synthesized through Fmoc solid-phase peptide synthesis to compare their molecular transporter efficiency. The chemical structures of the final products were confirmed by high-resolution MALDI-TOF. Final compounds were purified by a reversed-phase HPLC. The cytotoxicity of linear and cyclic peptides was evaluated in SK-OV-3 (human, epithelial ovarian adenocarcinoma), CCRF-CEM (human, lymphoblast peripheral blood), and HEK-293 (human, epithelial embryonic kidney healthy) cells using the MTS assay. The peptides did not exhibit any significant cytotoxicity at the concentration of 10 μM in CCRF-CEM, HEK-293, and SK-OV-3 cells after 3 h incubation. The cellular uptake of a fluorescence-labeled phosphopeptide (F′-GpYEEI) and anti-HIV drugs (lamivudine (F′-3TC), emtricitabine (F′-FTC)), where F′ is carboxyfluorescein, were measured in the presence of the peptide in CCRF-CEM and SK-OV-3 cells. Among all peptides, [(RW)5K](WR)5 (10 μM) was the most efficient and improved the cellular uptake of F′-GpYEEI (2 μM) by 13-fold when compared with F′-GpYEEI alone. These data suggest the potential of hybrid cyclic-linear peptides as molecular transporters.

Hybrid cyclic-linear cell-penetrating peptides containing alternative positive and hydrophobic residues as molecular transporters

ACS Spring Meeting 2021

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