From fullerene amino acids to fullerene peptides
Barron, Andrew R.
Doctor of Philosophy
A great challenge for biological application of fullerene material is the lack of solubility and constructive building blocks for further derivatization. Toward this end, we have developed a new approach to synthesize fullerene-based amino acids based on a Diels-Alder functionalization of C 60 and C70. The fullerene adducts can be readily purified by silica column chromatography with decent yield (40-45%) and characterized by MALDI-TOF, 1H and 13C NMR. This new strategy provides a facile and powerful means to prepare not only fullerene-based amino acids of C60 and C70, but also fullerene adducts with different functionality. Electrochemical study showed the fullerene cores of fullerene amino acids are basically intact. The Boc and Fmoc protected fullerene amino acids can couple to natural amino acids as desired. In addition, the deprotected fullerene amino acid has shown to be an effective antioxidant but without acute toxicity. The application of fullerene derivatives in medicinal field is the forefront of fullerene research. Our current result shows that fullerene amino acids are very versatile building blocks in bionanotechnology as we can readily incorporate these unnatural amino acids into peptide chains into with potential structural and biological applications via solid phase peptide synthesis. Conventional Fmoc chemistry utilizes nucleophiles deprotection agents such as piperidine and DBU that can react with fullerene core. To overcome this problem, we adopt a combination of Fmoc and Boc strategy by adding Boc-Baa at the end of N-terminal of peptide chains, which led to pure products with good yield. In our study, three classes of different peptides were synthesized with relative large scale. The addition of fullerene amino acids into peptide chains produces fullerene peptides with important structural and biological implications. Intracellular drug delivery and targeted diagnostic probe delivery are of the utmost importance in drug development, disease diagnosis and disease treatment. The presence of a fullerene-based amino acid acts as a passport for intracellular delivery, allowing the transport of cationic fullerene peptides into HEK-293, HepG2, and neuroblastoma cells where the peptides in the absence of the fullerene amino acid cannot enter the cell. The NLS fullerene peptide, H-BAA-Lys(FITC)-Lys-Lys-Arg-Lys-Val-OH, can actively cross over the cell membrane and accumulate significantly around the nucleus of HEK-293 and neuroblastoma cells, while H-BAA-Lys(FITC)-Lys8-OH accumulates in the cytoplasm. The addition of the fullerene amino acid does not actively facilitate anionic peptides delivery into the cytoplasm, while it actively assist cationic peptides to cross over cell membrane. Although the studies on the structural and biological application of fullerene peptides are still very limited, more and more evidences have pointed us a new family of nanomaterials with profound applications.
Inorganic chemistry; Organic chemistry