Advances in injectable hydrogels with biological and physicochemical functions for cell delivery

Injectable hydrogels that can be administered via syringes have enormous potential as cell delivery carriers for cell transplantation therapy. Owing to their beneficial properties, including biocompatibility, biodegradability, tissue adhesion, and scaffold functions, injectable hydrogels can be used to improve the delivery efficacy and survival of transplanted cells posttransplantation. Moreover, delivery via injection does not require culture or invasive surgical procedures, leading to reduced costs, processing time, and patient burden. To develop injectable hydrogels for clinical translation, hydrogels have been functionalized using various biological and physicochemical engineering approaches to induce angiogenesis, suppress immune rejection, provide viscoelasticity, and allow pore formation for cell infiltration. This focus review discusses the design of optimal injectable hydrogels for cell delivery. Moreover, this focus review summarizes the different approaches available to improve the biological and physicochemical features of hydrogels, lists their impacts on cellular functions, and highlights their therapeutic efficacy. Injectable hydrogels hold promise as cell delivery carriers for cell transplantation therapy in regenerative medicine. Injectable hydrogels possess various benefits, including biocompatibility, biodegradability, tissue adhesive properties, scaffold functions, and minimal invasiveness. To overcome the barriers in clinical translation, biological and physicochemical functionalization, which can improve delivery efficacy to the target and graft survival posttransplantation, is desirable. This review discusses the strategies to design injectable hydrogels for cell delivery and summarizes the approaches available to improve the biological and physicochemical features of hydrogels.