Zinc peroxide-coated gold nanorods as the therapeutic adjuvants for photothermal enhanced chemodynamic therapy and metalloimmunotherapy against tumor.

INTRODUCTION Traditional tumor therapies have limited efficacy, leading to a high mortality rate. Although immunotherapy holds considerable therapeutic promise, clinical immunotherapy for solid tumors only elicits durable responses in a minority of patients. This limitation is largely attributed to the highly immunosuppressive nature of the tumor microenvironment (TME). Notably, conventional chemodynamic therapy (CDT) is hampered by endogenous hydrogen peroxide (H2O2) shortage in tumor cells, and AZP compensates this defect via in-situ H2O2 self-supplementation to amplify hydroxyl radical generation.

Objectives

To develop a nanoplatform capable of systematically enhancing anti-tumor immunity, we rationally constructed a PEGylated zinc peroxide-coated gold nanorod (AZP) as a therapeutic adjuvant with acid-responsive properties for the combination therapy of cancer.

Methods

Gold nanorod-based adjuvants coated with zinc peroxide were successfully prepared via chemical oxidation, followed by PEGylation. The morphology and size of the AZP were characterized using transmission electron microscopy (TEM) and hydrodynamic diameter measurements. The elemental composition of AZP was determined by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy analysis. The acid-responsive degradation and photothermally enhanced catalytic properties of AZP were evaluated using TEM, inductively coupled plasma mass spectrometry, absorption spectroscopy, and thermal imaging tracing. The therapeutic mechanism of AZP at the cellular level was investigated through a series of experiments, including TEM, fluorescence imaging, immunofluorescence assays, Seahorse analysis, western blotting, and bioinformatics approaches, which comprehensively clarified the anti-tumor mechanism of AZP. Bilateral tumor and metastatic tumor models were established to verify the anti-tumor efficacy and mechanism of AZP at the animal level. Specifically, fluorescence imaging, immunofluorescence staining, tissue staining analysis, enzyme-linked immunosorbent assay, and flow cytometry were performed to assess the in vivo therapeutic effects.

Results

In the acidic TME, the AZP nanoplatform releases H2O2 and zinc ions, which increases the reactive oxygen species level in cancer cells. Additionally, due to its photothermally enhanced peroxidase-like activity, AZP induces the generation of more hydroxyl radicals under light irradiation. These effects synergistically disrupt lysosomes and mitochondria in tumor cells, block autophagy, and ultimately lead to tumor cell death. Furthermore, zinc supplementation by AZP enhances the activation of the cyclic GMP-AMP synthase and stimulator of interferon genes (cGAS-STING) pathway. Meanwhile, the combined treatment induces immunogenic cell death of cancer cells, which promotes the release of tumor-associated antigens and activates robust anti-tumor immune responses. Notably, intratumoral injection of the AZP adjuvant combined with irradiation effectively eradicates in situ tumors. When further combined with PD-1 antibody, this regimen can induce anti-tumor immunity, significantly inhibiting tumor growth, metastasis, and recurrence in a murine model without causing obvious toxicity.

Conclusion

The AZP nanoplatform exhibits excellent therapeutic efficacy, providing a rational design strategy for a potent adjuvant that integrates photothermally enhanced chemodynamic therapy and metalloimmunotherapy for the treatment of solid tumors.