Membrane adsorption and binding, cellular uptake and cytotoxicity of cell-penetrating peptidomimetics with α-peptide/β-peptoid backbone: Effects of hydrogen bonding and α-chirality in the β-peptoid residues

Cell-penetrating peptides (CPPs) provide a promising approach for enhancing intracellular delivery of therapeutic biomacromolecules by increasing transport through membrane barriers. Here, proteolytically stable cell-penetrating peptidomimetics with alpha-peptide/beta-peptoid backbone were studied to evaluate the effect of alpha-chirality in the beta-peptoid residues and the presence of guanidinium groups in the alpha-amino acid residues on membrane interaction. The molecular properties of the peptidomimetics in solution (surface and intramolecular hydrogen bonding, aqueous diffusion rate and molecular size) were studied along with their adsorption to lipid bilayers, cellular uptake, and toxicity. The surface hydrogen bonding ability of the peptidomimetics reflected their adsorbed amounts onto lipid bilayers as well as with their cellular uptake, indicating the importance of hydrogen bonding for their membrane interaction and cellular uptake. Ellipsometry studies further demonstrated that the presence of chiral centers in the beta-peptoid residues promotes a higher adsorption to anionic lipid bilayers, whereas circular dichroism results showed that alpha-chirality influences their overall mean residue ellipticity. The presence of guanidinium groups and alpha-chiral beta-peptoid residues was also found to have a significant positive effect on uptake in living cells. Together, the findings provide an improved understanding on the behavior of cell-penetrating peptidomimetics in the presence of lipid bilayers and live cells. (C) 2012 Elsevier B.V. All rights reserved.