Bufalin CaCO₃ Nanoparticles Triggered Pyroptosis through Calcium Overload via Na⁺/Ca²⁺ Exchanger Reverse for Cancer Immunotherapy

Bufalin is a promising active ingredient in traditional Chinese medicine but has shown limited anticancer applications due to its toxicity. Here, we report BCNPs@gel, a bufalin-containing CaCO₃ nanoparticle hydrogel, for enhancing cancer treatment through inducing cellular pyroptosis. Under the tumor microenvironment's low pH conditions, bufalin and Ca²⁺ are released from the delivery system. Bufalin serves as a direct anticancer drug and a Na⁺/K⁺-ATPase inhibitor by forcing the Na⁺/Ca²⁺ exchanger to reverse its function, which transfers Ca²⁺ into cytoplasm and ultimately causes Ca²⁺ overload-triggered pyroptosis. Meanwhile, we found that bufalin can upregulate PD-L1 in tumor cells. In combination with the PD-1 antibody, the delivery system showed a greater performance during the cancer treatment. BCNPs@gel enhances antitumor efficiency, reduces systemic side effects, extends antitumor mechanism of bufalin, and provides new strategies for inducing pyroptosis and calcium overload in cancer immunotherapy via Na⁺/K⁺-ATPase inhibitor. This work provides an application model for numerous other traditional Chinese medicine ingredients.