Cell Behavior and Complex Mechanical Properties of 3D Printed Cell-Laden Alginate-Gelatin Macroporous Mesostructures.

Bioprinting involves additive manufacturing of materials containing living cells, known as bioinks, which are formulated from cytocompatible hydrogel precursors. The bioink's characteristics before, during, and after crosslinking are critical for its printability, structural resolution, shape fidelity, and cell viability. The mechanical properties of printed constructs can be strongly influenced by their macroporous mesostructure, including pore size, filament diameter, and layer height, and are crucial for the intended applications in tissue engineering or regenerative medicine. It is known that the mechanical properties of hydrogels influence cell performance, but in turn, cells can also alter the mechanical properties of bioprinted constructs, which remain poorly understood. To explore these interdependencies, we selected an alginate-gelatin hydrogel (ALG-GEL), due to its well-known biocompatibility, combined with U87 cells and bioprinted three different multilayer macroporous mesostructures with varying porosity and filament diameter. We investigate how different macroporous mesostructures affect cells, how cells, in turn, influence mechanical properties, and whether the stability and mechanical properties of bioprinted macroporous mesostructures change over time. Our findings show that the bioprinted constructs are stable over the course of 14 days and highlight that cells can significantly influence their mechanical properties. This has important implications for biofabrication and tissue engineering applications.