(755a) De Novo Design of Bioactive Protein-Resembling Nanospheres Via Dendrimer-Templated Peptide Amphiphile Assembly

Peptide amphiphiles (PAs) are capable of self-assembly into micelles which can be used in the targeted delivery of peptide therapeutics and diagnostics. PA micelles exhibit a structural resemblance to proteins by having folded bioactive peptides displayed on the exterior of a hydrophobic core. However, PA self-assembly often results in high aspect ratio cylindrical micelles. Here we report a modular approach for controlling the self-assembly of biorelevant PAs into spherical, sub-100 nm structures by using dendrimers as supramolecular templates. The model PAs used in this investigation were: (1) di-C₁₆-bZip, a DNA binding PA sequence adapted from the alpha helical yeast transcription factor GCN4, which self-assembles into micron-long cylindrical micelles, and (2) di-C₁₆-NLS, a cell internalization PA, which self-assembles into polydisperse vesicles 100 to 400 nm in diameter.

The dendrimers were found to have a dramatic effect on the self-assembly of both model PAs, as the templating was successful for fabricating protein-resembling templated nanopsheres (PRTNs) averaging 50 nm in diameter. It was found that the PRTNs had a lower critical aggregation concentration than the PAs alone due to the presence of the hydrophobic dendrimer, which translated to an increase in PRTN stability in serum relative to the PA-only assemblies. Circular dichroism (CD) of di-C₁₆-bZip showed that the PAs within the PRTNs possessed enhanced alpha helical content compared to the unaggregated peptide. The bZip PRTNs were able to bind DNA and maintain their spherical geometry along the strands as observed with fluorescence assays and atomic force microscopy (AFM). Fluorescence resonance energy transfer (FRET) between fluorescently labeled di-C₁₆-bZip and di-C₁₆-NLS co‑assembled onto dendrimers indicated that mixed 50 nm PRTNs possessing both DNA binding and cell internalizing functions were formed. Cell internalization studies of fluorescently labeled PRTNs showed distinct fluorescent spots, indicative of internalization via endocytosis. With these qualities, the PRTNs have potential in applications that necessitate the delivery of small multifunctional protein-like therapeutics and diagnostics.