didn't get why gelatin over collagen. It is kind of obvious and explicitly mentioned that gelatin/hydrogel is very weak as a construction material (there is a reason why nature uses collagen which is polymerized gelatin (or gelatin being the broken down collagen)), and the small thin 2D patch scaffold made out of it is already an achievement that this article is dedicated too, and it is hardly scaleable beyond that, at least not into 3D structures, i.e. dead end for the most of organ engineering, while there is no such issues with collagen.