Hierarchical Structure of the Fibrillar Hydrogel Network of a Self‐Assembled Synthetic Peptide Revealed by X‐ray Scattering and Atmospheric Scanning Electron Microscopy

Abstract

SummaryWe herein developed a self‐assembling peptide with the ability to form a gel in water at pH ∼7 (SPG‐178 (a self‐assembling peptide gel with the amino acid sequence #178; [CH3CO]‐RLDLRLALRLDLR‐[NH2]; R = arginine, L = leucine, D = aspartic acid, and A = alanine). Leucine residues were employed to increase the hydrophobic interaction of SPG‐178 in water, which was one of the important driving forces of self‐assembly, and stabilize fibrillar hydrogel formation. The hierarchical structure of the fibrillar hydrogel of the peptide was analyzed using small/wide angle X‐ray scattering measurements (SAXS and WAXS), atomic force microscopy (AFM), transmission electron microscopy (TEM), and atmospheric scanning electron microscopy (ASEM). SAXS, AFM, and TEM measurements revealed the fibril nano‐structure of the self‐assembled peptide; the width of the fibril was ∼5 nm, which coincided with the length of one molecule in the β‐sheet structure revealed by FT‐IR and WAXS in water. ASEM permitted in situ observations, even in water, without freezing. The fibrillar network structure of the gel (micrometer scale) was directly visualized using ASEM measurements.