The self-assembly of biomolecular building blocks plays an increasingly important role in the discovery of new materials and scaffolds, with a wide range of applications in nanotechnology.[1,2] In particular, peptides and bile acids are widely investigated because of their biological role and their potential as building blocks in the preparation of nanostructured biomaterials. This work comes along with a research field focusing on the preparation of amphoteric compounds merging the bile acid scaffold and hydrophobic amino acids, thus combining the self-assembly properties of both bile acid- and peptide- based compounds.
We herein report the study of a novel derivative in which a L-Tryptophan has been introduced in the position C-3 of cholic acid. Such amino acid has been chosen since, together with its well-known self-assembly features, it renders the molecule of special interest as a fluorescently labeled biological compound.
The obtained compound is an amphoteric fluorescent labeled bile acid and we demonstrate that it shows a pH-dependent self-assembly, which is extremely different compared compared to the one of its natural precursor. In alkaline conditions it self-assembles forming micelles whereas in acidic conditions it self-organizes in elongated assemblies that grow with time forming a hydrogel. The auto-association process has been investigated by means of circular dichroism, dynamic light scattering, atomic force microscopy, UV-Vis and fluorescence spectroscopy.
[1] E. Busseron, Y. Ruff, E. Moulin and N. Giuseppone, Nanoscale, 2013, 5, 7098
[2] L. Travaglini, A. D’Annibale, K. Schillén, U. Olsson, S. Sennato, N. V. Pavel, and L. Galantini, Chem. Commun., 2012, 48, 12011
luciano.galantini@uniroma1.it
