title: Self-assembly of pH and calcium dual-responsive peptide-amphiphilic hydrogel.
abstract: 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.
authors.affiliation: Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, China.
authors.forename: Xi-Rui
authors.initials: XR
authors.lastname: Zhou
authors.forename: Rui
authors.initials: R
authors.lastname: Ge
authors.forename: Shi-Zhong
authors.initials: SZ
authors.lastname: Luo
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002118:Calcium / Q000737:chemistry*; D002942:Circular Dichroism; D055119:Elastic Modulus; D020100:Hydrogels / Q000138:chemical synthesis*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D057139:Nanofibers / Q000737:chemistry / Q000648:ultrastructure; D009842:Oligopeptides / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D020100:Hydrogels; D009842:Oligopeptides; D013501:Surface-Active Agents; D002118:Calcium
keywords: calcium response; hydrogel; pH sensitive; peptide amphiphile; self-assembly