Tea Polyphenol Coordinated with Nanoparticles of ZIF-8 and Coated with Polydopamine and PEG for Immuno-Oncotherapy

Epigallocatechin-3-gallate (EGCG), the most abundant tea polyphenol, possesses excellent anti-inflammation properties. Emerging studies proved its potent potential as an immune checkpoint (ICP) inhibitor for anticancer therapy. However, the low bioavailability of EGCG reduces its treatment efficiency. In this work EGCG-based nanomedicine EGCG-ZIF-8@PDA-PEG (EZP) was developed via the coordination between ZIF-8 MOF and EGCG, followed by polydopamine and PEG functionalization for efficient tumor-targeting EGCG delivery. Results demonstrated that the EGCG loading rate in EZP reached up to 85%. Both in vitro and in vivo studies proved that the EZP nanoparticles were capable of inhibiting the expression of ICP molecules and modulating the inflammatory tumor microenvironment, evidenced by the suppression of PD-L1 expression, the reduction of inflammatory cytokines, and the resultant decline in the number of immunosuppressive cells, for instance, myeloid-derived suppressor cells, tumor-associated macrophages, and regulatory T cells. These synergistic effects significantly improved the infiltration of dendritic cells and T cells in tumors, realizing an inspiring antitumor effect.