pH-Responsive Zinc Ion Regulating Immunomodulatory Nanoparticles for Effective Cancer Immunotherapy

Herein, we introduce a novel approach involving the utilization of a human serum albumin-coated zeolite imidazolate framework-8 containing a photosensitizer (HPZ) that exhibits targeted recognition of the tumor microenvironment, enabling the rapid elevation of zinc ion concentrations while facilitating the controlled release of an encapsulated photosensitizer (PS). At a physiological pH of 7.4, HPZ demonstrates a size of approximately 170 nm, significantly decreasing to less than 10 nm under pH 6.5 acidic conditions. Acid-induced decomposition of HPZ triggers a rapid increase in zinc ion concentration, eliciting potent cytotoxic effects against colorectal, breast, and pancreatic cancers. Additionally, upon laser irradiation, the encapsulated PS within HPZ initiates the generation of reactive oxygen species, synergistically augmenting the cytotoxicity induced by zinc ions. Intravenous administration of HPZ in a CT26 tumor-bearing mouse model resulted in a notable expansion of CD3⁺CD4⁺ helper T cells and CD3⁺CD8⁺ cytotoxic T cells, accompanied by a reduction in the CD4⁺CD25⁺Foxp3⁺ regulatory T-cell population. These changes led to significant inhibition of tumor growth, highlighting the efficacy of HPZ in this experimental model. Importantly, HPZ exhibits favorable safety characteristics, displaying no toxicity toward vital organs and inducing no weight loss. Thus, HPZ holds immense promise as a standalone treatment or in combination with diverse anticancer immunotherapies, underscoring its potential in the field of anticancer immunotherapy.