Chemical gelling of hydrogels-based biological macromolecules for tissue engineering: Photo- and enzymatic-crosslinking methods

Newly, injectable hydrogels have been renowned as promising biomaterials and appropriate candidates for tissue engineering which can be applied for the development of 3-dimensional cell culture models. Hydrogels have in situ formability that allows an actual and homogeneous drugs/cells encapsulation, and suitable for in vivo surgical operation in a minimally invasive way, causing less discomfort for patients. A wide and varied range of methods has been applied to design hydrogels-based biological macromolecules via chemical gelling techniques, such as photo-polymerization, and enzyme-catalyzed reactions due to the biocompatibility and feasible processing of in situ formation of hydrogels and the easy implantation through in situ injection of hydrogels-based biological macromolecules. This present review covers the current advances in the development of injectable hydrogels through enzymatically and photo-crosslinking procedures for tissue engineering. The characteristics and applications of natural and synthetic base materials used in hydrogel generation are also reviewed with an outline on biomedical considerations. (C) 2019 Published by Elsevier B.V.