Generation of Self‐Assembled Structures Composed of Amphipathic, Charged Tripeptides for Intracellular Delivery of Pro‐Apoptotic Chemotherapeutics

Chemotherapeutic drugs remain the most efficacious treatment options for a many human cancers. However, the inability to deliver these drugs directly to cancerous cells often results in dose limiting and sometimes life-threatening adverse effects. Rather than developing new chemical moieties, researchers have begun focusing on the development of drug carriers, which are specifically designed to shuttle chemotherapeutics into malignant cells while sparing healthy cells. Charged nanoparticles have emerged as effective delivery platforms for several xenobiotic classes including anticancer agents, oligonucleotides and antibodies. Notably, peptide-based self-assembled nanostructures are of particular interest due to their biocompatibility, high drug loading capacity, and potential for customization for cell-specific targeting. We synthesized and studied the self-assembling properties of two charged, cell penetrating tri-peptides: H2N-Arg-Leu-Phe-OMe (S1) with Arg as cationic amino acid and Boc-Phe-Leu-Glu-OH (S2) with Glu as negatively charged amino acid. The fibrils and spherical self-assembled structures formed by S1 and S2, respectively, can encapsulate the chemotherapeutic drug Doxorubicin and facilitate intracellular drug delivery via endocytosis. Furthermore, S1- and S2-encapsulated Doxorubicin (Dox-S1, Dox-S2), like the unencapsulated drug, induced oxidative stress and mitochondrial dysfunction, activated the ATM/p53 signaling cascades, and triggered apoptosis in cancer cells. Thus, while the surface charge of molecular building blocks used to generate supramolecular assemblies influences the morphology of generated nanostructures, both cationic and anionic peptide-based assemblies are capable of functioning as drug delivery vehicles.