Bioactive photocrosslinkable resin solely based on refined decellularized small intestinal submucosa for digital light processing 3D printing of in vitro tissue mimics

Three-dimensionally (3D) printed tissue mimics are a unique in vitro platform for studying human pathophysiology in a more physiologically relevant manner compared to oversimplified 2D cell cultures and complex animal models. Furthermore, they can be used for replacing parts of damaged tissue or organs. However, their 3D printing requires an availability of materials that at the same time show a high level of biomimicry and also have a suitable viscosity profile and crosslinking kinetics for the desired printing technique. We developed a new biomimetic material for the digital light processing stereolithography (DLP SLA) 3D printing by solubilizing and functionalizing porcine small intestine submucosa (dSIS) into photocrosslinkable dSIS methacrylamide (dSIS-MA) and by subsequently formulating it into a bioactive 3D printing resin. The concentration of 1.5 weight-% of dSIS-MA yielded desired viscosity and photocrosslinking kinetics, and the 3D printing of the resin resulted in fully transparent and highly swelling dSIS-MA hydrogels with a stiffness resembling native intestinal tissue. Both human small intestine organoid-derived undifferentiated primary cells and immortalized human Caco-2 cells grew to confluency on the 3D printed hydrogels without additional cell-adhesive precoating and formed continuous tight junctions, thereby demonstrating the suitability of the material for growing a (personalized) intestinal epithelium. Furthermore, both immortalized human HT29-mtx cells and a part of the human primary intestinal cells produced mucin 5AC, demonstrating bioactivity by early differentiation of these cells on the photocrosslinked dSIS-MA hydrogels. The new dSIS-MA resin was 3D printed into intestine-mimicking scaffolds that desirably guided the seeded human intestinal cells to grow along the 3D villi architectures. The detected cell compatibility of the new dSIS-MA material combined with its high printability and biomimicry indicated that this new material can be an excellent tool for modelling and reproducing native tissue architectures where enhanced physiological relevancy is desired.