Background UV exposure continues to induce many health issues, though commercial sunscreens are available. Novel UV filters with high safety and efficacy are urgently needed. Metal–organic frameworks (MOFs) could be a suitable platform for UV filter development, due to their tunable optical, electrical, and photoelectric properties by precise controlled synthesis. Results Herein, four zinc-based MOFs with various bandgap energies were chose to investigate their optical behaviors and evaluate their possibility as sunscreens. Zeolitic imidazolate framework-8 (ZIF-8) was found to possess the highest and widest UV reflectance, thereby protecting against sunburn and DNA damage on mouse skin and even achieving a comparable or higher anti-UV efficacy relative to the commercially available UV filters, TiO2 or ZnO, on pig skin, a model that correlates well with human skin. Also, ZIF-8 exerted appealing characteristics for topical skin use with low radical production, low skin penetration, low toxicity, high transparency, and high stability. Conclusion These results confirmed ZIF-8 could potentially be a safe and effective sunscreen surrogate for human, and MOFs could be a novel source to develop more effective and safe UV filters. Graphical Abstract

The immunosuppressive tumor microenvironment (TME) severely limits the clinical applications of cancer immunotherapy. Herein, a hypoxia‐responsive delivery system is constructed simply by coordinating ferric (Fe3+) with mitoxantrone (MTO), sulfasalazine (SAS), and hypoxia‐sensitive dopamine derivative of polyethylene glycol (PEG) using “one‐pot” reaction for the “closed‐loop” synergistic enhancement of ferroptosis and immunotherapy. Hypoxia‐sensitive PEG ensures the integrity of delivery system in circulation to prevent the premature leakage of drugs, and the detachment of PEG in the interior hypoxic TME can facilitate the deep penetration and the subsequent tumor uptake. The released iron and MTO induce the generation of reactive oxygen species (ROS), while SAS inhibits the elimination of lipid peroxides by inhibiting SLC7A11 subunit of glutamate‐cystine antiporter, which synergistically induces immunogenic ferroptosis to promote dendritic cells maturation and T cells activation. The activated CD8+ T cells then release interferon γ (IFN‐γ) and in turn enhance ferroptosis by downregulating the expression of SLC7A11. As a result, the “closed‐loop” synergistic enhancement between ferroptosis and immunotherapy significantly prevents tumor growth and prolonged survival time of tumor‐bearing mice with no obvious systemic toxicity. The excellent therapeutic effect together with the scalable synthesis and controllable quality will promise its translation to clinic as a novel immunotherapy.

The internalization of antigens by dendritic cells (DCs) is the initial critical step for vaccines to activate the immune response; however, the systemic delivery of antigens into DCs is hampered by various technical challenges. Here we show that a virus-like gold nanostructure (AuNV) can effectively bind to and be internalized by DCs due to its biomimetic topological morphology, thereby significantly promoting the maturation of DCs and the cross-presentation of the model antigen ovalbumin (OVA). In vivo experiments demonstrate that AuNV efficiently delivers OVA to draining lymph nodes and significantly inhibits the growth of MC38-OVA tumors, generating a ∼80% decrease in tumor volume. Mechanistic studies reveal that the AuNV-OVA vaccine induces a remarkable increase in the rate of maturation of DCs, OVA presentation, and CD4+ and CD8+ T lymphocyte populations in both lymph node and tumor and an obvious decrease in myeloid-derived suppressor cells and regulatory T cell populations in spleen. The good biocompatibility, strong adjuvant activity, enhanced uptake of DCs, and improved T cell activation make AuNV a promising antigen delivery platform for vaccine development.

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