Abstract
Bioprinting with cell-laden hydrogels (bioink) requires the careful mixing of cells with the hydrogel carrier to ensure that the bioink is homogeneous and functional, and the printing results are reproducible. Bioink preparation is therefore a critical process step that must accommodate the specific rheological properties of different bioinks. Here, we developed a reproducible method for the optimized mixing of cells and hydrogel carriers that can be integrated into current bioprinting processes. First, we tested and optimized different mixing devices for their effect on bioink homogeneity and rheological properties, resulting in a low-shear process for the preparation of homogenous bioinks. Based on these findings, we evaluated the impact of different cell densities on the rheological profile of bioinks according to shear and temperature, and estimated the impact of shear stress intensity and duration on 1.1B4 cells. Finally, we integrated the optimized mixing method into a current printing process and monitored the printed construct for 14 days to confirm cell viability. We found that the cell viability in the printed cell-laden constructs remained in excess of 91% after 14 days.
Highlights
Biofabrication involves the production of functional complex tissues, addressing many of the limitations of cell therapy and cell-based screening models [1,2]
Several bioprinting technologies have been developed, including inkjet and laser printing options, but extrusion-based bioprinting (EBB) is almost the most widespread because it is compatible with viscous carrier materials and high cell densities, both of which are favorable for tissue reconstruction and regeneration [3]
A significant difference in cell viability was observed between non-embedded cells and cells that had been embedded in carrier material by mixing with a spatula [5], whereas the printing step had relatively little additional impact, perhaps due to error propagation following the mixing process [5,6,7]
Summary
Biofabrication involves the production of functional complex tissues, addressing many of the limitations of cell therapy and cell-based screening models [1,2]. One of the most promising forms of biofabrication is 3D printing (bioprinting) with cell-laden carrier material (bioink). Several bioprinting technologies have been developed, including inkjet and laser printing options, but extrusion-based bioprinting (EBB) is almost the most widespread because it is compatible with viscous carrier materials and high cell densities, both of which are favorable for tissue reconstruction and regeneration [3]. Biofabrication involves the preparation and mixing of components, the printing step, and post-processing steps such as cross-linking to mature the construct and maintain its properties in situ. The preparation and mixing of components before printing is a key process step and may have an even greater impact on the performance of the resulting construct than the printing process. A significant difference in cell viability was observed between non-embedded cells and cells that had been embedded in carrier material by mixing with a spatula [5], whereas the printing step had relatively little additional impact, perhaps due to error propagation following the mixing process [5,6,7]
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