Print parameter optimisation for a Pluronic F-127 and alginate hybrid hydrogel

Pneumatic-based extrusion as a 3D bioprinting technique is used for the fabrication of tissue constructs. Biopolymers are used to create a hydrogel that is used as the biomaterial ink to fabricate intricate tissue scaffolds able to simulate pathophysiological conditions more accurately than 2D models. There is a delicate balance between the parameters facilitating complex structures without affecting the printed scaffold results, and therefore the influence of each parameter should be fully understood. The aim of this study was to systematically optimise the printing parameters required to successfully 3D bioprint a computer-aided design (CAD) model with a preformulated hybrid hydrogel. A commercial bioprinter with a pneumatic printhead the BioX™ was used with conical print nozzles. A hybrid hydrogel with 6% (w/v) alginate and 23% (w/v) Pluronic F-127 (PF127), displayed printability, high porosity, low degradation, non-Newtonian rheology and were used in the printing parameter optimisation part of the study. Parameters that were optimised included: nozzle size, printing speed, extrusion pressure and temperature. The parameter optimisation index (POI), printability and shape fidelity were used to determine the optimal printing parameters. This was used in combination with a newly formulated scoring system to determine printing accuracy of the scaffold. Parameters that yielded a 100% complete scaffold print was a nozzle size of 27G using an extrusion pressure of 70 kPa and printing speed of 30 mm/s at 37 °C. These printing parameters did not yield the best results in all printability indices evaluated. It was concluded that the visual observations in combination with quantitative grading methods of the scaffolds, were a similarly important factor to take into consideration when selecting the optimal printing parameters.