Abstract text (incl. figure legends and references)
Introduction: Bioprinting is a growing field of tissue engineering, offering a potential solution to global corneal graft shortages. Ensuring printability for extrusion bioprinting is crucial. Investigating rheological behavior is a key to achieving this goal.
Objectives: To assess printability quickly, a method with a simple hydrogel containing alginate and hyaluronic acid was created. Four rheological methods were selected to evaluate different aspects of hydrogels.
Materials and Methods: A design of experiments with varying concentrations and combinations was developed. Rheological properties were assessed using rotational and oscillatory rheological methods. Rotational sweeps provided information on shear thinning, while oscillatory sweeps yielded information on the storage modulus, loss modulus, and damping factor. Both methods combined provided insights on the recovery time, simulating extrusion and recovery. For extrusion printing, a Bioscaffolder 3.3 was used. Another DoE examined the effects of printing speed and pressure values on printability. Printability was visually evaluated.
Results: All hydrogel formulations exhibited shear thinning behavior. Increasing the concentration resulted in higher apparent viscosity. Moreover, an increase in concentrations led to a prolongation of the recovery time. Hydrogels with concentrations of lower than 20 mg/ml were not evaluable in terms of printability. However, increased storage modulus correlated with enhanced printability. A damping factor between 0.65 and 0.9 demonstrated improved printability compared to lower or higher values, indicating optimal gel consistency.
Conclusion: Assessing printability based on rheological behavior is a complex task. While a short recovery time is usually desired, these results may suggest that parameters such as higher viscosity and a specific damping factor may exert greater influence. For corneal bioprinting this information may be valuable for identifying a suitable bioink.