Scaffolds and templates for cell penetration and peptide ligation

Yannick Fillon, Purdue University

Abstract

The delivery of therapeutic agents to cellular targets is a topic of great interest. Recently cationic peptides have proven useful in delivering cargoes to cells. We have designed a rigid scaffold based on the polyproline helix capable of displaying cationic moieties in a controlled fashion to enhance cellular delivery. In this regard we synthesized a set of novel amino acid containing cationic and hydrophobic residues by O-alkylation of hydroxyproline. Each of these amino acids was incorporated into a growing peptide chain to yield a range of cationic polyproline peptides of various length and composition. A dramatic increase in cellular uptake was achieved with peptides containing guanidinium groups. Amphilicity also played a key role in enhancing cellular uptake. Our most potent agent was over 10 times more efficient at cellular delivery as compared to that of the well-studied Tat peptide, while displaying minimal cytotoxicity. This topic was further expanded with the design and synthesis of a range of non-peptidic branched molecules containing 2, 4 and 8 guanidinium moieties. These agents contained an alcohol linker to allow for the versatile attachment of therapeutics and their controlled release under in vivo conditions, thus creating cationic prodrug molecules. The molecules were tested for cellular uptake by flow cytometry. The compounds containing 4 and 8 guanidinium moieties showed increased uptake by 10-fold and 2-fold respectively as compared to the Tat peptide. Recently, trimethylammonium functionalized gold nanoparticles (GNPs) were shown to promote the helicity of negatively charged peptides. Studies have also focused on functionalized gold nanoparticles for catalysis of reactions that involve bond cleavage. However, the use of nanoparticles to assist bond forming reactions is relatively unexplored and has not been realized for biomolecular systems. We used gold particles to template the folding and ligation of negatively charged peptide fragments. We found that the helicity of peptides E1, E2 and E1E2, and the ligation between peptide fragments was promoted with the addition of GNPs. Ongoing research in this area includes the design of new peptides capable of self-replication from their respective fragments on the surface of the functionalized GNPs.

Degree

Ph.D.

Advisors

Chmielewski, Purdue University.

Subject Area

Biochemistry|Organic chemistry|Biomedical research

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