Solvent-annealed triple-helix reconstituted schizophyllan hydrogels with mechanically tunable and injectable properties.

Schizophyllan (SPG) is a natural polysaccharide with excellent biocompatibility, yet its use in hydrogels is often hampered by the need for cytotoxic chemical cross-linkers and a lack of injectability. To overcome these limitations, we introduce a solvent-exchange-assisted wet-annealing method that facilitates the reversible dissociation and reconstitution of SPG's triple-helical structure, yielding a purely physical, injectable hydrogel. By tuning annealing temperature and time, the elastic modulus and fracture strength can be varied over an order of magnitude. Gelation proceeds via DMF-mediated helix dissociation followed by temperature-driven re-assembly, where long SPG chains entangle and bridge adjacent triple helices to create load-bearing yet reversible physical junctions. The resulting semi-flexible network resists small strains but shows shear-thinning behavior for facile syringe injection. In vitro studies show >95 % NIH/3 T3 viability, and in vivo subcutaneous implantation in mice elicits only transient inflammation that resolves within 28 days. These findings establish SPG hydrogels as a safe, mechanically tunable over a wide range platform for minimally invasive biomedical applications.