Nano-immunotherapy combining PD-L1 blockade with Ca2+-mediated immune activation

Acid-responsive aPD-L1@CaP/A23187 enhances PD-L1 checkpoint blockade. • CaP nanoparticles encapsulate aPD-L1 and release it selectively in acidic TME. • Ca²⁺ from CaP synergizes with A23187 to boost Ca²⁺ influx and immune signaling. • The formulation elevates intracellular Ca²⁺, promotes DC maturation, and M1 polarization. • In vivo, it increases tumor accumulation, inhibits growth, reverses TME, and induces immune memory. Immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 axis have revolutionized cancer therapy, but their efficacy is restricted by the highly immunosuppressive tumor microenvironment and is often accompanied by systemic toxicities.To overcome these limitations, we developed a novel acid-responsive nanoplatform, aPD-L1@CaP/A23187, integrating anti–PD-L1 antibodies (aPD-L1) with calcium phosphate (CaP) nanoparticles and the Ca 2+ ionophore A23187. CaP nanoparticles encapsulated aPD-L1 with high efficiency and stability, enabling tumor-specific release under acidic conditions while minimizing systemic distribution. Simultaneously, Ca 2+ released from CaP synergized with A23187 to promote transmembrane Ca 2+ influx, thereby activating downstream Ca 2+ signaling pathways in immune cells. In vitro, this formulation increased intracellular Ca 2+ levels, induced dendritic cell maturation, and polarized macrophages toward the pro-inflammatory M1 phenotype. In vivo, aPD-L1@CaP/A23187 achieved ∼7.4-fold higher tumor enrichment than free antibody, exhibited potent tumor suppression in TC-1 tumor–bearing mice. Mechanistic studies revealed enhanced dendritic cell activation, robust CD8 + T cell infiltration and granzyme B secretion, reduced Treg proportions, and M1 macrophage polarization, collectively reversing the immunosuppressive tumor microenvironment. Importantly, treatment also induced durable effector memory T cell responses in a distant tumor model, providing protection against tumor recurrence and metastasis. These findings highlight the Ca 2+ -assisted nanoplatform offers a broadly applicable strategy for next-generation cancer immunotherapy.