ROS-scavenging ultrasonicated graphene oxide/alginate microgels for mesenchymal stem cell delivery and hindlimb ischemia treatment

Mesenchymal stem cell (MSC) transplantation is widely recognized as a promising treatment for peripheral artery diseases because of their unique ability to secrete multiple growth factors and immunomodulatory cytokines. However, direct administration of MSCs frequently results in insufficient therapeutic efficacy due to low viability and poor retention at the implantation site. The delivery of MSCs in microsized hydrogels allows for simple injection, improved retention, and enhanced cell protection. However, the high oxidative stress present in ischemic tissues significantly impairs the viability and therapeutic activity of transplanted MSCs. This study aimed to develop a simple and effective method for fabricating reactive oxygen species (ROS)-scavenging microgels to enhance the MSC efficacy for ischemic hindlimb treatment. Specifically, tip-sonicated graphene oxide (GO)/alginate (sGO/alginate) microgels exhibited significantly increased antioxidizing activity against various ROS compared with pristine GO/alginate microgels. MSCs encapsulated in sGO/alginate microgels (MSC/sGO/alginate) demonstrated higher viability than those encapsulated in alginate or GO/alginate microgels under various oxidative stress conditions. Furthermore, human umbilical vein endothelial cells co-cultured with MSCs encapsulated in sGO/alginate microgels formed more tubes under both normal and H2O2-treated conditions, implying enhanced pro-angiogenic potential of the MSCs. In vivo experiments using hindlimb ischemia mouse models revealed significant improvements in blood perfusion, limb salvage, vascularization, and MSC survival in the MSC/sGO/alginate group compared with the other groups (MSC, MSC/alginate, and MSC/GO/ alginate). The strategy developed in this study offers a straightforward and powerful method for treating various ROS-related diseases, including ischemia.