Impact of the composition of alginate and gelatin derivatives in bioconjugated hydrogels on the fabrication of cell sheets and spherical tissues with living cell sheaths

Gelatin and alginate derivatives possessing phenolic hydroxyl moieties (gelatin–Ph and Alg–Ph) were dissolved in aqueous solution and conjugated via horseradish peroxidase-catalyzed crosslinking, resulting in hydrogelation. The objective of creating the hydrogels was to prepare cell sheets and spherical tissues wrapped in living cell sheaths. An increase in the gelatin–Ph content in the hydrogel improved cellular adhesion on the hydrogel surface but hindered degradability by alginate lyase. A hydrogel with the desired characteristics was obtained from a solution containing 0.5% (w/v) gelatin–Ph and 1.5% (w/v) Alg–Ph. Human aortic endothelial (HAE) cells and mouse embryo fibroblast 10T1/2 cells grew on the hydrogels and could be harvested as cell sheets by treatment with alginate lyase. 10T1/2 cells enclosed in Alg–Ph/gelatin–Ph microcapsules composed of the conjugate hydrogel elongated on the inner surface of the microcapsules and grew three times faster than those enclosed in Alg–Ph microcapsules. Alg–Ph/gelatin–Ph microcapsules not only supported growth of the enclosed cells into spherical tissues, but also provided a cell adhesive outer surface for the fabrication of an HAE cell layer. Finally, spherical tissues of 10T1/2 cells wrapped in living HAE cell sheaths were obtained by treatment with alginate lyase.