Tunable metallo-hydrogels: Mechanical properties and characterization of stimuli responsive self-assembling peptide hydrogels

Supramolecular self-assembly is employed in this study to design short amphiphilic peptides with specific binding affinity for Zn(II). Two selectively modified peptides (Ac-LIVKHH-NH2, P1 & Fmoc-LIVKHH-NH2, P2) were synthesized using standard Fmoc-/Boc- solid-phase peptide synthesis. When these water-soluble peptides are combined with Zn(II) salt solution, they encapsulate large volumes of water to form metallo-hydrogels. The Zn(II) responsiveness in metallo-hydrogels was investigated in buffer or water (pH 7) with or without Zn(II) salts. The afforded supramolecular architectures (metallo-hydrogels) were characterized by circular dichroism and their micro- and nanostructure with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Measurements of rheology and thixotropy were conducted to assess the gelation behavior, the viscoelastic character and the mechanical properties of metallo-hydrogels. We found that Zn(II) significantly influences hydrogel formation, leading to improved mechanical properties. The resulting hydrogels show remarkable thixotropic behavior, indicating their potential in 3D printing and as injectable carriers. Such hydrogels can be also used as primary wound dressings, and their antibacterial activity can be further explored. This research work provides valuable insights into the zinc-responsive behavior of the aforementioned peptides, establishing a foundation for their prospective applications in biomaterials and materials science.