Stable Protein-Based G-Quadruplex-Derived Supramolecular Bioinks as Tunable ECM-Mimetic Constructs Assembled by Combining Non-Covalent and Covalent Strategies.

G-quadruplex hydrogels hold great promise for biofabrication owing to their dynamic supramolecular nature, provided their inherent instability under physiological conditions is overcome. Here, a bioinspired strategy that synergistically combines supramolecular self-assembly, under macromolecular crowding conditions, with in-bath enzymatic covalent crosslinking was employed to create stable, protein-based G-quadruplex-derived hydrogels. Mimicking the crowded intracellular milieu, the addition of Ficoll enhances G-quadruplex stability and tunes the rheological behavior, while transglutaminase-mediated crosslinking reinforces the network, preserving its structural integrity over extended periods. This combined approach yields printable bioinks with optimal viscosity, yield stress, and shear-thinning properties, enabling the fabrication of complex, multilayered 3D constructs that support enhanced cell viability and proliferation within an extracellular matrix (ECM)-mimetic fibrillar environment. Moreover, the modulation of the crosslinking density allows controlling cellular responses, offering a versatile platform for tailoring the biomechanical microenvironment. This study establishes a new class of hybrid G-quadruplex hydrogel bioinks, exhibiting unprecedented stability under physiological conditions, biofunctionality, and off-the-shelf availability, unlocking their potential for advanced tissue engineering and regenerative medicine strategies.