pH-Controlled Hierarchical Self-Assembly of Peptide Amphiphile

The self-assembling behavior of peptide amphiphiles can be leveraged upon to form complex nanostructures that have a wide range of applications. Herein we present a study on the lateral assembly of peptide amphiphile nanofibers into higher order structures by designing complementary attracting designer sequences, made up of oppositely charged amino acids, on the surface region of the nanofibers. The surface charge of the individual amino acids can be selectively altered as the pH is raised above or below their pK(a) value, and this enables the regulation of interfiber and intrafiber interactions. We demonstrated that pH which triggers alternating positively and negatively charged surface sequence enables interdigitating and bundling of nanofibers, while pH which results in negatively charged surface sequence discourages lateral assembly of nanofibers. This pH-responsive system is able to self-assemble into micelles, nanofibers, and bundles nanofibers, providing a new perspective toward the fabrication of novel nanostructures.