Alginate is widely utilized as a biomaterial owing to its excellent safety profile, biocompatibility, and ability to form hydrogels via “egg-box” structures with divalent cations. Various gelation technologies have been developed to date, however, the internal gelation method using calcium carbonate (CaCO₃) has attracted considerable attention for its ability to control gel morphology and improve structural uniformity. Nevertheless, this method typically requires the addition of acidifying agents to facilitate the release of Ca 2+ from CaCO₃, which consequently lowers the pH of the gel and may adversely affect biocompatibility. To address this issue, recent studies have explored alternative gelation strategies that enhance biocompatibility, including the use of carbon dioxide (CO₂). In this approach, CO₂ acts as an acidifying agent during gelation and is released from the gel afterward, thereby suppressing post-gelation acidification. Furthermore, this gelation method enables control of cell adhesion through hybridization with other polymers, broadening the application range of gels as biomaterials. The use of CO 2 has been also shown to promote the formation of porous network structures, which may enhance nutrient and gas permeability, contribute to cell migration, thereby promoting cell organization. This review summarizes recent progress in CO 2 -induced alginate hydrogels for biomedical applications, and further discusses the extension of alginate hydrogel–CO 2 interactions in algae cultivation as an application in the environmental field. • Anionic polysaccharide hydrogels, alginate and low-methoxy pectin forming egg-box structures with high biocompatibility. • Traditional gelation using acidifying agent and CaCO 3 may leave residual acid, lowering pH and potentially causing cell damage. • CO 2 -induced gelation enables the release of CO 2 from the hydrogel after gelation, thereby preventing acidification. • CO 2 -mediated hydrogels with porous structure have applications for biomaterials such as wound dressings and cell scaffolds. • Further studies in physicochemical property, long-term stability, and cellular interactions may expand potential of this study.
Teshima et al. (Fri,) studied this question.