Due to the similarity of the physical properties of hydrogels to those of living tissues, various hydrogels have been studied over the past 20 years as implantable biomaterials that demonstrate good compatibility with soft tissues. Despite their unique properties, the applications of traditionally prepared and pre-shaped hydrogels are limited. Since they lack injectable fluidity, implanting them subcutaneously can cause significant discomfort for patients. To address this issue, injectable polymer materials have been developed that exist as a fluid solution at room temperature but transition from a sol to a gel structure after being injected into living tissues. These types of hydrogels are attractive systems for regenerative medicine applications due to their minimally invasive delivery via a syringe, ease of application, the ability to easily and homogeneously incorporate cells and bioactive molecules before gelation, minimal toxic effects, and enhanced patient comfort levels.