Manganese ion gradient liposomes modified by disulfide bond enhance cellular uptake and tumor immunity

As an activator and alarm signal for tumor innate immune therapy, manganese ions can activate the stimulator of interferon genes (STING) pathway directly or indirectly. However, due to their high positive charge, manganese ions cannot freely penetrate biological membranes, and it is challenging to target them to the cells. Liposomes have been widely used as an effective drug delivery system. Using metal ions as active carriers to establish a gradient is an effective way to load chemotherapy drugs, but its low delivery efficiency and significant degradation of effective drugs by lysosomes may result in reduced therapeutic effects. In this study, we constructed an active drug-loading liposome (LMD@LA) that enters cells through thiol-mediated endocytosis to encapsulate both the chemotherapy drug doxorubicin and manganese ions to achieve sustained manganese ion release. The combination of chemotherapy-induced immunogenic cell death and innate immune therapy with manganese ions was used to treat tumors. The liposome was able to reverse the immunosuppressive tumor microenvironment, reduce the resistance of B16F10 and 4T1 tumors to doxorubicin, and decrease the migration and invasion abilities of tumors by binding with lipoic acid.