Development of a bacteria-nanosapper for the active delivery of ZIF-8 particles containing therapeutic genes for cancer immune therapy.

Specific tumor-targeted gene delivery remains an unsolved therapeutic issue due to aberrant vascularization in tumor microenvironment (TME). Some bacteria exhibit spontaneous chemotaxis toward the anaerobic and immune-suppressive TME, which makes them ideal natural vehicles for cancer gene therapy. Here, we conjugated ZIF-8 metal-organic frameworks encapsulating eukaryotic murine interleukin 2 () expression plasmid onto the surface of VNP20009, an attenuated strain with well-documented anti-cancer activity, and constructed a TME-targeted delivery system named /ZIF-8@. Both and experiments demonstrated that /ZIF-8@ maintained the tumor-targeting feature of bacteria, and could be effectively phagocytosed by intratumoral macrophages, thus leading to the expression and secretion of IL2 in TME. The detailed analysis of tumor immune microenvironment (TIME) showed that one dose of combinatorial /ZIF-8@ achieved synergistic actions on a potent remodeling of TIME, marked by the activation of cytotoxic T cells and M1-polarization of macrophages in TME, thus leading to significant anti-tumor effects in melanoma, orthotopic hepatocellular carcinoma, and pulmonary metastasis models. More importantly, /ZIF-8@ exhibited high safety to major organs and hematopoietic systems. Taken together, we report a novel plasmid/ZIF-8@ system that simultaneously achieves effective TME-targeted delivery of therapeutic gene, as well as synergistic re-activation of TIME.