Synthesis, properties, and biomedical applications of alginate methacrylate (ALMA)-based hydrogels: Current advances and challenges

Alginate methacrylate (ALMA) hydrogels have been prevalently used in various biomedical applications, mainly due to their photocrosslinking ability. Not only this feature allows the formation of cell-laden hydrogels, but it also facilitates the fine-tuning of hydrogels' physical attributes such as mechanical properties, pore size distribution, and degradation rate. In the past decade, various modifications were applied to ALMA hydrogels to amend their physiochemical and biological properties to enhance their performance in tissue engineering applications. Moreover, the advent of microfabrication technologies further expanded the horizon of ALMA hydrogels by facilitating the fabrication of microstructures with controlled architecture. Remarkably, these improvements opened up new avenues in biomedical research to study cell-cell interactions and cell morphogenesis in response to microstructural cues. Aside from that, ALMA hydrogels were successfully used for the regeneration of multiple tissues, including bone, cartilage, and muscle, among others. Given the current state of research on ALMA hydrogels, it is timely to map the evolution of these hydrogels and review the collective work on this topic. Herein, we have provided an extensive review of ALMA-based hydrogels covering a broad spectrum of issues on this topic, including synthesis methods, tuning of physical properties, organic/inorganic composites, microfabrication, and tissue engineering applications. Lastly, future directions regarding the application of ALMA-based hydrogels in developing advanced materials and technologies are discussed.