Enzymatically triggered glucose-releasing scaffolds as nutritional supports for millimeter-scale tissue engineering

Construction of millimeter-sized tissues to mimic real human tissue or organ is still challenging, as oxygen and nutrients have a diffusion limit of only 100-200 μm from blood vessels. Almost all mammalian cells except red blood cells and platelets need a glucose supply to support their metabolic activities and functions. Inspired by the properties of blood vessels, we developed an alginate scaffold that is capable to release glucose by hydrolysis of glycogen via enzymes such as amyloglucosidase in this study. The scaffold can be flexibly shaped into glucose-releasing capsules (Glc-RCs) and glucose-releasing fibers (Glc-RFs). It was demonstrated that Glc-RCs can provide sustained release of glucose for up to 4 days and have no negative effect on C2C12 mouse myoblast cell and human adipose-derived mesenchymal stem cell proliferation. Glc-RCs could also support differentiation of C2C12 into myotubes after 7 days of application without the need for media replenishment. Glc-RFs were incorporated into millimeter-scale 3D tissue-engineered constructs, where they reduced the apoptotic activity of normal human dermal fibroblasts (NHDFs) located within approximately 1000 μm from the fibers. In particular, the relationship between glucose diffusion distance and resulting cellular responses like apoptosis has not previously been documented in other glucose-releasing material studies. Thus, the developed glucose-releasing scaffold has the potential to be shaped into different sizes by 3D extrusion printing to serve as a localized glucose delivery system to further study glucose diffusion profiles as well as supplying glucose for supporting mm-sized tissue construction.