Self-assembly of thiolated versus non-thiolated peptide amphiphiles

The self-assembly properties of peptide amphiphiles make them attractive for a range of applications, such as scaffolds for cell culture, drug delivery vehicles, or as stabilizing coatings for nanoparticles. The latter application requires derivatization of the amphiphiles to enable them to bind to, and interact with, a surface. This can be achieved by introduction of a thiol which facilitates binding to gold surfaces for example. However, small changes to the composition of peptide amphiphiles can have a large impact on their self-assembly behavior. Therefore, we have synthesized and characterized a range of amphiphiles with different peptide sequences, alkyl chain lengths, and with or without a terminal thiol. We have characterized their structure and self-assembly using circular dichroism (CD) spectroscopy, attenuated total reflection infrared (ATR-IR) spectroscopy, and transmission electron microscopy (TEM). We discuss how changes to the peptide sequence and alkyl chain affect self-assembly and compare the self-assembly properties of thiolated and non-thiolated amphiphiles. Such knowledge not only provides fundamental insights as to how self-assembly can be controlled, but will also be helpful in determining which amphiphiles are most suitable for use as stabilizing nanoparticle coatings.