Described herein are compositions comprising at least two diblock copolypeptides, wherein each copolypeptide has an ionic segment with the opposite charge from the other. The copolypeptides form β-sheet structured hydrogel assemblies via polyion complexation when mixed in aqueous media. As a result of their unique physical properties, the hydrogels are useful as cell suspension or cell culture media, in drug or cell delivery systems, in scaffolds for tissue repair, or as 3d-printable media.
