3D bioprinting of photocrosslinkable hydrogel constructs

Three-dimensional (3D) bioprinting comprises a group of biofabrication technologies for the additive manufacturing of 3D constructs by precisely printing biocompatible materials, cells and biochemicals in predesigned spatial positions. These technolo- gies have been successfully applied to fabricate biodegradable 3D constructs with intricate architectures and heterogeneous composi- tion, assuming a pivotal role in the field of tissue engineering. However, the full implementation of bioprinting strongly depends on the development of novel biomaterials exhibiting fast crosslinking schemes and appropriate printability, cell-compatibility and biome- chanical properties. Photocrosslinkable hydrogels are attractive materials for bioprinting as they provide fast polymerization under cell-compatible conditions and exceptional spatiotemporal control over the gelation process. Photopolymerization can also be per- formed during the bioprinting to promote the instantaneous formation of hydrogel with high well-defined architecture and structural stability. In this review paper, we summarize the most recent developments on bioprinting of photocrosslinkable biodegradable hydro- gels for tissue engineering, focusing on the chemical modification strategies and the combination of photocrosslinking reactions with other gelation modalities.