(591c) Non-Charged Cell-Penetrating Oligothioetheramides

The discovery of cell-penetrating peptides (CPPs) over two decades ago uncovered a novel method for transporting a variety of cargoes into cells.¹ Although promising, CPPs have several drawbacks that hinder their use for in vivo therapeutic applications such as rapid metabolic degradation by proteases and a propensity for mounting an immune response. Recently, the Alabi research group developed a unique approach for the rapid assembly of sequence-defined oligothioetheramides (oligoTEAs).² OligoTEAs have three distinct advantages over native peptides. First, sequence-defined oligomers are abiotic and not susceptible to protease degradation, thus increasing their bioavailability. Second, access to direct modification of the oligoTEA backbone enables direct control over their conformation, rigidity, and pendant group spacing to ultimately tune interactions between the binding motifs and the cell membrane. Last, the use of readily accessible synthetic monomers will allow for massive compositional diversity.

Studies conducted on several CPPs thus far indicates that a combination of cationic and hydrophobic residues are critical for translocation across cellular membrane.^3,4,5 Based on these and many other studies, we embarked on the assembly of an 8-residue oligoTEA library composed of a hydrophilic backbone (DL-1,4-dithiothreitol) and distinct combinations of two different pendant groups: a cationic (guanidinium) monomer and a hydrophobic (benzyl) monomer. Probing this initial library of 16 oligomeric structures for cellular uptake led to the conclusion that for this class of macromolecules, cationic residues are not a requirement for efficient uptake. In fact, they seem to impede uptake. Expanding our library with further studies reveals the unusual discovery of a non-charged cell penetrating oligoTEA that undergoes efficient cellular uptake with no cytotoxicity, and outperforms R9K, a well-known and widely used CPP. This talk will focus on the sequence-controlled assembly of this non-charged cell penetrating oligoTEA, its uptake efficiency across a variety of cell lines, and its mechanism of cell entry.

References: 1. K.M. Stewart et al. Org Biomol Chem 6, 2242-2255 (2008) 2. M. Porel et al. J Am Chem Soc 136, 13162-13165 (2014) 3. D.J. Mitchell et al. J Pept Res 56, 318-325 (2000) 4. N. Svensen et al. Angew Chem Int Ed 50, 6133-6136 (2011) 5. C.B. Cooley et al. J Am Chem Soc 131, 16401–16403 (2009).