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Abstract
CD8+ T cells play an important role in anti-tumor immunity response. However, tumor could often evade immune surveillance by deactivating antitumor T cell responses. Ionomycin (ION)/phorbol 12-myristate 13-acetate (PMA) combination is commonly used to activate T cell in vitro. Research shows that ION (a Ca2+ carrier through cell membrane) mainly activates the calcineurin-NFAT signally pathway, while PMA activates protein kinase C (PKC) and NF-κB pathway. This stimulator cocktail mimics the full activation by T cell receptor signaling and co-stimulation of T cell. However, no evidence showed that ION/PMA could bring clinical benefits when applied in vivo due to its systematic toxicity and off-targets effect. Herein, we designed a CaCO3-based nanoparticle and optimized its structure so that it can be easily dispersed in aqueous solution with PEG conjugated to the outer layer for longer circulation time in system. We also conjugated αPD-1 to the nanoparticles after screening common markers for CD8+ T cells to ensure the targeting ability. PMA is loaded into the nanoparticles due to the hydrophobic interaction. This CaCO3-based nanoparticle (PDCNP-Ab) could bring Calcium and PMA into T cell specifically through its targeting ability and thus activate T cell and enhance its anti-tumor immunity. This salt-based nanoparticle is also non-toxic to the body system and can be easily excreted.Our results demonstrate successful synthesis of the nanoparticles with desired size and controlled release profile. PDCNP-Ab specifically binds and internalizes into T cells, leading to increased intracellular calcium ion concentration, confirming successful nanoparticle delivery. We observed significant upregulation of activation markers, including CD69, TNF-α, and IFN-γ, on OT-1 cells, indicating T cell activation. Analysis of tumor-infiltrating T cell profiles in vivo reveals that PDCNP-Ab can transform the immunosuppressive tumor microenvironment into an immunostimulatory one. Importantly, PDCNP-Ab exhibits potent tumor inhibition efficacy as a monotherapy, in combination with radiation therapy, or in conjunction with cell therapy in both local and metastatic tumor models. These nanoparticles hold great promise for clinical applications aimed at enhancing T cell immunity against tumors.