Development of 3D bioprinted GelMA-alginate hydrogels with tunable mechanical properties

3D bioprinting is gaining attention as a biofabrication technique due to its potential to recreate the complex structure of native human tissue, combining high precision additive manufacturing, biocompatible inks, cells and biochemical factors. In this work, we evaluated the combination of covalent and ionic crosslinking networks as a strategy to modulate the properties of hydrogel inks and stripe-pattern printed structures to induce anisotropic mechanical properties. We found that for optimum printing, gelMA-alginate concentrations should be between 11 and 15% w/v and the polymer ratio and concentration modulate the rheological and compressive moduli of hydrogels. Furthermore, degradation and swelling rates are also adjustable, with some blends showing less than 20% degradation and negligible swelling over a 14 days period. Sheep adipose derived stem cells were included in three formulations and cell viability was >75% after bioprinting in all hydrogels. Stripe-patterned hydrogels were successfully printed using a dual printhead allowing us to modify the mechanical properties of 3D printed hydrogel scaffolds in each axis. The printed structure with gelatin (10% w/v) and gelMA-alginate (8% w/v - 7%w/v) hydrogel stripes showed a noticeable anisotropic mechanical behaviour. Thus, we demonstrated that chemical and structural factors could modulate the properties of printed biocompatible hydrogels, including anisotropic mechanical behaviour, with potential application in tissue engineering.