Guest-responsive supramolecular hydrogels expressing selective sol–gel transition for sulfated glycosaminoglycans

This paper describes the stimuli-responsive hydrogels constructed from bola-type amphiphiles composed of two dipeptides containing phenylalanine attached to the ends of a hydrophobic tetrathiophene. The hydrogel formation ability of the amphiphiles was affected by the N-terminal amino acid residue, which is an amphiphile-possessing phenylalanine-lysine sequence that formed a hydrogel under limited pH conditions. Gel formation occurred because of the phase transition of the gelator assembly from a granular aggregate to a fibrous architecture, in a process controlled by pH. This stimuli-responsive sol–gel transition was also accomplished by the addition of an anionic polymer, and sulfated glycosaminoglycans were successfully discriminated using the hydrogel system.