An integrated in silico–in vitro approach for bioprinting core–shell bioarchitectures

Biological tissues possess a high degree of structural complexity characterized by curvature and stratification of different tissue layers. Despite recent advances in in vitro technology, current engineering solutions do not comprise both of these features. In this paper, we present an integrated in silico–in vitro strategy for the design and fabrication of biological barriers with controlled curvature and architecture. Analytical and computational tools combined with advanced bioprinting methods are employed to optimize living inks for bioprinting-structured core–shell constructs based on alginate. A finite element model is used to compute the hindered diffusion and crosslinking phenomena involved in the formation of core–shell structures and to predict the width of the shell as a function of material parameters. Constructs with a solid alginate-based shell and a solid, liquid, or air core can be reproducibly printed using the workflow. As a proof of concept, epithelial cells and fibroblasts were bioprinted respectively in a liquid core (10 mg/mL Pluronic) and in a solid shell (20 mg/mL alginate plus 20 mg/mL gelatin, used for providing the cells with adhesive moieties). These constructs had a roundness of 97.6% and an average diameter of 1500 ±136 μm. Moreover, their viability was close to monolayer controls (74.12% ± 22.07%) after a week in culture, and the paracellular transport was twice that of cell-free constructs, indicating cell polarization.