Stimuli responsive fibrous hydrogels from hierarchical self-assembly of a triblock copolypeptide.
In this work, the self-assembly behavior and pH responsiveness of a triblock copolypeptide in aqueous media are demonstrated. The copolypeptide was composed of a central pH responsive poly(l-glutamic acid) (PGA), flanked by two hydrophobic poly(l-alanine) blocks (PAla) (PAla5-PGA11-PAla5). This system showed a pH-responsive transition from short tapes to spherical aggregates by increasing the pH, as a result of deprotonation of the PGA block and a conformational change from α-helix to random coil. Increasing the ionic strength to physiological conditions (0.15 M) has triggered fibrillar self-assembly through intermolecular hydrogen bonding of PAla end-blocks that form β-sheet nanostructures, in conjunction with charge screening of the central random coil PGA segments. At elevated concentrations a thermo-responsive free supporting hydrogel was obtained, consisting of rigid β-sheet based twisted superfibers, resulting from hierarchical self-assembly of the copolypeptide. Yet, morphological transformation of this nanostructure was observed upon switching the pH from physiological conditions to pH 4. An unexpected morphology constituted of α-helix-based giant nanobelts was observed as a consequence of the secondary peptide transitions.
Department of Chemical Engineering, University of Patras, 26504, Patras, Greece. ct@chemeng.upatras.gr.
Maria-Teodora
MT
Popescu
George
G
Liontos
Apostolos
A
Avgeropoulos
Constantinos
C
Tsitsilianis
D000409:Alanine / Q000737:chemistry; D018698:Glutamic Acid / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D009994:Osmolar Concentration; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary
D020100:Hydrogels; D010455:Peptides; D018698:Glutamic Acid; D000409:Alanine