DESIGNING COILED-COIL PEPTIDE MATERIALS FOR BIOMEDICAL APPLICATIONS

  Peptide biomaterials have drawn great attention in recent decades owing to their tunability and biocompatibility. Coiled-coils specifically have become a well-studied scaffold with a clear sequence-to-structure relationship. As such, the Chmielewski lab has extensively studied peptide assemblies based on the GCN4 leucine zipper. First, we present the peptide TriCross, where nitrilotriacetic acid (NTA) and di-histidine ligands are installed at the N- and C-terminus, respectively, and a bipyridine ligand installed at a central, solvent exposed position. Through strategic placement of these metal-binding ligands, TriCross assembled into a three-dimensional (3D) mesh in the presence of zinc ions and dissembled following mild ethylenediaminetetraacetic acid (EDTA) treatment. These properties created a 3D network capable of encapsulating cells for extended periods of time (>1 week) and releasing cells upon metal-chelation. 

  Next, we describe a stabilized nanotube and enhanced crystal assembly through a heterocoiled-coil assembly. Nanotubes composed of the coiled-coil peptide TriNL that assembled likely through ionic interactions rapidly degraded in phosphate buffered saline (PBS). To improve stability, a peptide with metal-binding ligands, p2L, was introduced through thermal annealing of the two peptides. Low levels of p2L (up to 10:1 TriNL:p2L) retained nanotube morphology while simultaneously introducing NTA and di-histidine ligands. Upon addition of metal, metal-ligand interactions were established within the nanotube and increased stability of the material. Higher levels of p2L (2:1 TriNL:p2L) led to hexagonal crystals similar to p2L but now without the use of metal ions. These crystals expanded the scope of protein inclusion by removing the requirement for His-tags on proteins to be incorporated within the material.

  Finally, a self-replicating and self-assembling coiled-coil peptide is reported. The coiled-coil TriNL was cysteine modified (N20C) to create a peptide capable of native chemical ligation. At low concentrations, the N20C FL peptide acted as a template for the cysteine and thioester fragments while high concentrations led to fibrillar structures. The size of the fibrils was controlled through the addition of preassembled seeds into the native chemical ligation system.