An Overview of Hydrogel-Based Bioinks for 3D Bioprinting of Soft Tissues

It has been widely perceived that three-dimensional bioprinted synthetic tissues and organ can be a clinical treatment option for damaged or diseased tissue repair and replacement. Conventional tissue engineering approaches have limited control over the regeneration of scaffold geometries and cell distribution. With the advancement of new biomaterials and additive manufacturing techniques, it is possible to develop physiologically relevant functional tissues or organs with living cells, bioactive molecules and growth factors within predefined complex 3D geometries. In this perspective, this review discusses how hydrogel-based bioinks can be used to mimic native tissue-like extracellular matrix environment, with optimal mechanical and structural integrity for patient-specific tissue regeneration, in reference to advanced bioprinting technologies to bioprint multitude of multicomponent bioinks. This review also summarizes various bioprinting techniques, the gelation and biodegradation mechanisms of hydrogel-based bioinks, the properties required for ideal bioink, challenges to design bioinks, as well as reviews the fabrication of 3D printed cardiac tissue, cartilages, brain-like tissue, bionic ear, and urinary system.