Hypoxia-Responsive Nanoscale Coordination Polymer Enhances the Crosstalk Between Ferroptosis and Immunotherapy

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.     

Metal-Based Nanozymes with Multienzyme-Like Activities as Therapeutic Candidates: Applications,Mechanisms, and Optimization Strategy

Most nanozymes in development for medical applications only exhibit single-enzyme-like activity, and are thus limited by insufficient catalytic activity and dysfunctionality in complex pathological microenvironments. To overcome the impediments of limited substrate availabilities and concentrations, some metal-based nanozymes may mimic two or more activities of natural enzymes to catalyze cascade reactions or to catalyze multiple substrates simultaneously, thereby amplifying catalysis. Metal-based nanozymes with multienzyme-like activities (MNMs) may adapt to dissimilar catalytic conditions to exert different enzyme-like effects. These multienzyme-like activities can synergize to realize “self-provision of the substrate,” in which upstream catalysts produce substrates for downstream catalytic reactions to overcome the limitation of insufficient substrates in the microenvironment. Consequently, MNMs exert more potent antitumor, antibacterial, and anti-inflammatory effects in preclinical models. This review summarizes the cellular effects and underlying mechanisms of MNMs. Their potential medical utility and optimization strategy from the perspective of clinical requirements are also discussed, with the aim to provide a theoretical reference for the design, development, and therapeutic application of their catalytic effects.     

Cascade Immune Activation of Self-Delivery Biomedicine for Photodynamic Immunotherapy Against Metastatic Tumor

Photodynamic therapy (PDT) can generate reactive oxygen species (ROS) to cause cell apoptosis and induce immunogenic cell death (ICD) to activate immune response, becoming a promising antitumor modality. However, the overexpressions of indoleamine 2,3-dioxygenase (IDO) and programmed cell death ligand 1 (PD-L1) on tumor cells would reduce cytotoxic T cells infiltration and inhibit the immune activation. In this paper, a simple but effective nanosystem is developed to solve these issues for enhanced photodynamic immunotherapy. Specifically, it has been constructed a self-delivery biomedicine (CeNB) based on photosensitizer chlorine e6 (Ce6), IDO inhibitor (NLG919), and PD1/PDL1 blocker (BMS-1) without the need for extra excipients. Of note, CeNB possesses fairly high drug content (nearly 100%), favorable stability, and uniform morphology. More importantly, CeNB-mediated IDO inhibition and PD1/PDL1 blockade greatly improve the immunosuppressive tumor microenvironments to promote immune activation. The PDT of CeNB not only inhibits tumor proliferation but also induces ICD response to activate immunological cascade. Ultimately, self-delivery CeNB tremendously suppresses the tumor growth and metastasis while leads to a minimized side effect. Such simple and effective antitumor strategy overcomes the therapeutic resistance against PDT-initiated immunotherapy, suggesting a potential for metastatic tumor treatment in clinic.     

In Situ Embedding Hydrogen-Bonded Organic Frameworks Nanocrystals in Electrospinning Nanofibers for Ultrastable Broad-Spectrum Antibacterial Activity

In the event of a public health crisis, highly effective and sustainable antimicrobial materials and equipment will be urgently needed. Here, the preparation is reported by electrospinning of broad-spectrum antibacterial nanofibers embedded in a photoactive hydrogen-bonded organic framework (HOF) of rod-like nanocrystals ≈60 nm in length. The resulting HOF@PVDF-HFP nanofibers maintain excellent tensile and breathability characteristics while shielding HOF nanocrystals against acid and alkali corrosion. A series of nanofibers embedded with different amounts and types of HOF nanocrystals are prepared to optimize their efficiency of singlet oxygen (¹O₂) generation. The 0.5 wt.% HOF-101-F@PVDF-HFP nanofibers exhibit the most efficient ¹O₂ generation that is enhanced by a factor of almost 2 when compared with the HOF-101-F microcrystalline powder. The HOF@PVDF-HFP nanofibers are demonstrated to highly effectively kill pathogens, including viruses, bacteria, and fungi in 30 min under ambient light conditions.