Self‐assembly of pH and calcium dual‐responsive peptide‐amphiphilic hydrogel

Peptide‐based hydrogels have gained much interest for biomedical applications as a result of their biocompatibility. Herein, we reported a synthetic pH‐sensitive and calcium‐responsive peptide‐amphiphilic hydrogel. The sequences of the peptide amphiphiles were derived from the repeat‐in‐toxin (RTX) motif. At a certain peptide‐amphiphile concentration, self‐assembly was accompanied by the formation of a rigid, viscoelastic hydrogel at low pH or the presence of calcium ions. Circular dichroism spectra showed that the peptide amphiphiles adopted beta‐sheet structure. Meanwhile, as revealed by transmission electron microscopy, the peptide‐amphiphile self‐assembly was accompanied by the formation of long interconnected nanofibrillar superstructure. Material properties of the resulting peptide‐amphiphile hydrogel were characterized using oscillatory sheer rheology, and the storage modulus (G′) was found to be one order of magnitude higher than the loss modulus (G″), indicating a moderately rigid viscoelastic material. Furthermore, with systematical residue substitution, it was found that the aspartic acid within the repeat‐in‐toxin sequence of peptide amphiphiles was responsible for the pH and calcium selectivity. The environmental responsiveness, secondary structure, morphology, and mechanical nature of the peptide‐amphiphile hydrogel make it a possible material candidate for biomedical and engineering application. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.