Metal-polyphenol "prison" attenuated bacterial outer membrane vesicle for chemodynamics promoted in situ tumor vaccines.

As natural adjuvants, the bacterial outer membrane vesicles (OMV) hold great potential in cancer vaccines. However, the inherent immunotoxicity of OMV and the rarity of tumor-specific antigens seriously hamper the clinical translation of OMV-based cancer vaccines. Herein, metal-phenolic networks (MPNs) are used to attenuate the toxicity of OMV, meanwhile, provide tumor antigens via the chemodynamic effect induced immunogenic cell death (ICD). Specifically, MPNs are assembled on the OMV surface through the coordination reaction between ferric ions and tannic acid. The iron-based "prison" is locally collapsed in the tumor microenvironment (TME) with both low pH and high ATP features, and thus the systemic toxicity of OMV is significantly attenuated. The released ferric ions in TME promote the ICD of cancer cells through Fenton reaction and then the generation of abundant tumor antigens, which can be used to fabricate in-situ vaccines by converging with OMV. Together with the immunomodulatory effect of OMV, potent tumor repression on a bilateral tumor model is achieved with good biosafety. • Metal-phenolic network is first used for not only attenuating the toxicity of OMV but also fabricating in situ vaccines. • The smart synergism of in situ vaccines with TME reprogramming leads to robust tumor repression and immunological memory. • This convenient and reliable engineering strategy can be popularized in the construction of different bioactive formulations. [ABSTRACT FROM AUTHOR]