Amphiphilic self-assembling peptides: formulation and elucidation of functional nanostructures for imaging and smart drug delivery.

The rational design of self-assembled peptide-based nanostructures for theranostics applications requires in-depth physicochemical characterization of the peptide nanostructures, to understand the mechanism and the interactions involved in the self-assembly, allowing a better control of the objects' physicochemical and functional properties for theranostic applications. In this work, several complementary characterization methods, such as dynamic light scattering, transmission electron microscopy, circular dichroism, Taylor dispersion analysis, and capillary electrophoresis, were used to study and optimize the self-assembly of pH-sensitive short synthetic amphiphilic peptides containing an RGD motif for active targeting of tumor cells and smart drug delivery. The combined methods evidenced the spontaneous formation of nanorods (L = 50 nm, d = 10 nm) at pH 11, stabilized by β-sheets. To complement with imaging properties for diagnosis, a new strategy was developed by designing an optimized peptide sequence to allow for efficient functionalization with a contrast agent, while preserving the self-assembling properties. Co-assemblies of the peptide and its derivatives, after peptide modification with a gadolinium complex, exhibited similar nanorod structures and required properties for drug delivery and imaging applications in vivo.