Coassembly of oppositely charged short peptides into well-defined supramolecular hydrogels.

Two types of oppositely charged short peptides comprised of a hydrophobic N-fluorenyl-9-methoxycarbonyl (FMOC) tail and a peptide backbone were designed and prepared via a standard solid phase peptide (SPPS) technique. When mixing these two oppositely charged peptides in water at a neutral pH, a supramolecular hydrogel with fibroid morphology could be formed via the electrostatic attraction triggered coassembly. The spectroscopic techniques indicated that the hydrogen bonding interactions of the peptide backbones resulted in the formation of antiparallel beta-sheet like superstructure, and the fluorenyl rings connected to the peptide backbones were thus pi-stacked with each other through an antiparallel fashion in the formed nanofibers. Due to the weak flexibility of peptide chains and steric hindrance of rigid fluorenyl rings during the initial process of the coassembly of the oppositely charged peptides, a relatively slow self-assembly was presented, and a higher concentration of the oppositely charged peptides was necessary for this supramolecular hydrogel formation. The strategy demonstrated in this study can be developed as a convenient approach for different types of short peptides to coassemble into a supramolecular hydrogel with multiple functions for the biomedical applications.