(247c) Characterization of Cell-Laden Alginate-Gelatin Bioinks for Rapid 3D Printing of Artificial Tissues Models

In vitro drug screening of emerging medicines requires the production of artificial tissue models that closely mimic native tissue environments. Rapid artificial tissue development has shown promise through the use of bioprinting, as a biofabrication technique, for producing heterogeneous cell-laden hydrogels. A Limiting factor in rapid production of physiologically relevant tissue models is often attributed to difficulties in printing large populations of cells in bioinks. The production time of artificial tissues can be greatly reduced if the cell seeding density of the hydrogel is greatly increased. In this study, the influence of cell seeding density on the viscoelastic properties, printability, and viability of our alginate-gelatin bioinks, was examined. Immortalized human embryonic kidney (HEK) cells at three seeding densities were used to populate various hydrogel compositions. The viscoelastic behavior at varying cell densities for each hydrogel was tested using bulk rheology. Optimal printing parameters for each bioink composition were systematically determined for pneumatic extrusion-based bioprinting. Over a five-day period, we examined the viability of the encapsulated cells within the bioink. We observed an inverse relationship between cell concentration and zero-shear viscosity, in all hydrogel compositions. As cell seeding densities increase, the storage moduli decrease, thus lowering the required printing pressures used for hydrogel extrusion from the bioprinter. Next, increasing cell concentration was found to negatively impact the structural properties of the extruded material, by increasing filament spreading. Lastly, bioinks composed of high molecular weight alginates and the greatest cell-seeding densities yielded cell viabilities >80% and acceptable structural uniformity after printing. Bioinks with increased cell seeding density experienced a softening effect, allowing stiffer gels to be printed with smother filaments. The relationship between seeding density and mechanical properties of alginate-gelatin bioinks explored in this study may aid in the future rapid fabrication of functional tissue models for therapeutic screening.