Rheological characterisation and printability assessment of an optimised bioink for extrusion-based 3D bioprinting

The performance of extrusion-based 3D bioprinting depends critically on the rheology of bioinks, which must balance printability with post-deposition structural fidelity. Here we present a statistically optimised, human-compatible hydrogel formulation (hyaluronic acid, sodium alginate, Dextran-40), originally identified via Design of Experiment (DoE) methodology for target viscosity, and now subjected to comprehensive rheological validation. Flow curve analysis confirms the bioink's shear-thinning profile, supporting its suitability for extrusion. Oscillatory amplitude and frequency sweep tests reveal a stable viscoelastic response within the linear viscoelastic region. In combination with pronounced shear-thinning behaviour and rapid thixotropic recovery, this supports the bioink's ability to maintain structural integrity following deposition. A three-stage thixotropy test demonstrates rapid viscosity recovery following high shear, while temperature ramp testing shows expected increases in viscosity as temperature decreases, with no gelation observed in the printing-relevant range. Collectively, these findings validate the formulation's suitability for cell-laden printing applications and offer a reproducible rheological benchmark for future bioink development in soft tissue engineering.