Electrostatic Regulation of Bola-Amphiphilic Peptide Self-Assembly and Nanotube Formation Induced by Salt Ions

Peptide self-assembly into nanostructures offers substantial potential for applications in catalysis, drug delivery, and nanodevice fabrication. However, controlling the morphology of these assemblies remains a challenge. In this study, we investigate the role of salt ions in regulating the self-assembly of the bola-amphiphilic peptide KFFFFK, facilitating a transition from twisted fibrils to nanotubes. Using transmission electron microscopy, we show that the addition of NaCl induces the formation of nanotubes, and we detail the time-dependent assembly process. Increased salt concentrations reduce electrostatic repulsion, promoting the lateral merging of fibrils and supporting the formation of closed nanotubes. This phenomenon is also observed with several other salts. These findings underscore the critical role of electrostatic interactions in peptide self-assembly and highlight the importance of salt concentration in directing assembly pathways. Our results provide valuable insights into the mechanisms of peptide self-assembly and offer a versatile approach for designing advanced biomaterials and nanodevices based on well-defined peptide nanostructures.