Single synthetic peptide forms electrically polarized, self-healing hydrogel

Scientists from the RIKEN Center for Sustainable Resource Science and RIKEN Pioneering Research Institute in Japan, together with collaborators at the University of Münster in Germany, have developed a hydrogel built from a single synthetic peptide named FQ(Pyr). The peptide consists of phenylalanine and glutamine joined with a pyrene group attached to the side of glutamine. When dissolved in highly alkaline water and then gradually acidified to pH 4, the molecules self-assemble into a translucent gel.

Cryo-electron microscopy at 1.7 Å resolution revealed that the gel consists of uniform helical nanofibers. Each nanofiber contains five water-filled channels, including a central channel about 15 angstroms in diameter. The peptide molecules within each fiber all point in the same direction, creating an electrical polarization along the fiber axis. Water molecules inside the channels are also highly ordered.

The gel is mechanically strong and flexible. In tests, violent shaking broke the gel apart, but it fully healed within 24 hours and recovered its original quality. This self-healing ability combines with the polarized structure, which is unusual for peptide hydrogels that typically either have organized channels but weak mechanics, or strong mechanics but disordered internal structure.

The electrical polarization means the material can potentially transport ions, generate electrical signals when compressed, respond to electric fields, and interact with biological tissues in ways that conventional hydrogels cannot. The researchers suggest possible uses in electrically responsive artificial muscles and smart drug delivery systems triggered by electrical signals.

The work was led by Kenichiro Itami at RIKEN and is published in Nature Communications. The study demonstrates that a minimal molecular design — a single short peptide with a bulky aromatic side group — can produce a supramolecular structure with atomic-level order, emergent electrical properties, and autonomous repair.