After photocuring, the GelMA/bPE hydrogels displayed enhanced shear strength as compared to the corresponding GelMA hydrogels, indicating the synergistic contributions of covalent network and electrostatic self-assemblies. (Figure ). Precise tuning of shear properties was achieved by variation in bPE loading, thus granting access to suitable matrices for a wide range of tissue substrates (e.g., ~300 Pa for brain, ~600 Pa for liver, ~2.5 kPa for kidney, 12-100 kPa for skeletal muscle, > 100 kPa for cartilage and bone) . Moreover, the photocrosslinked GelMA/bPE hydrogels (and their corresponding inks) comprising bPEs with strongly interacting guanidinium and sulfonate moieties retained their shear strength in physiological salt conditions (approx. 0.1 M NaCl), such as in Dulbecco's phosphate-buffered saline (DPBS) or Dulbecco's modified eagle's medium (DMEM), while were prone to disassembly in highly salty environments (1 M NaCl) as a consequence of enhanced screening of electrostatic interactions (Figure ). As shown in previous studies, the level of salt and pH responsiveness is dependent on the strength of the ionic pair of the bPEs (strong: guanidinium and sulfonate vs. weak: ammonium and carboxylate), thus providing a flexible platform for the future design of adaptive hybrid hydrogels .