Creep of Alginate-Gelatin-Hyaluronic acid strands and cell viability after bioprinting

The success of 3D bioprinting in tissue engineering relies on i) precise bioink deposition for creating intricate tissue architectures and ii) good cell viability after printing. However, printed strands made of hydrogels are susceptible to time-dependent deformation -known as creep- which can compromise printing accuracy. Creep might be reduced by increasing the crosslink density, but this could be deleterious for cells in the bioink. Therefore, this study investigates the impact of creep on the printability of an Alginate-Gelatin-Hyaluronic acid bioink. Creep data were fitted with a linear rheological model that enables to predict the strand deformation over time. Furthermore, creep curves measured at different temperatures allow to determine an Arrhenius dependence of the parameters of the rheological model with time. The activation energies of the mechanisms involved in the rheological behavior of the bioink suggest that gelatin plays a significant role in the viscous response, while the network made by the entangled chains of alginate and hyaluronic acid is responsible for the anelastic deformation. This deformation decreased with simultaneous nebulization with CaCl2. Additionally, this bioink exhibited a high percentage of viable NIH/3T3 fibroblasts (78-90%) after 3D-bioprinting and Ca2+ immersion crosslinking processes.