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.