Bufalin CaCO<sub>3</sub> Nanoparticles Triggered Pyroptosis\nthrough Calcium Overload via Na<sup>+</sup>/Ca<sup>2+</sup> Exchanger\nReverse for Cancer Immunotherapy

Bufalin is a promising active ingredient in traditional\nChinese\nmedicine but has shown limited anticancer applications due to its\ntoxicity. Here, we report BCNPs@gel, a bufalin-containing CaCO<sub>3</sub> nanoparticle hydrogel, for enhancing cancer treatment through\ninducing cellular pyroptosis. Under the tumor microenvironment’s\nlow pH conditions, bufalin and Ca<sup>2+</sup> are released from the\ndelivery system. Bufalin serves as a direct anticancer drug and a\nNa<sup>+</sup>/K<sup>+</sup>-ATPase inhibitor by forcing the Na<sup>+</sup>/Ca<sup>2+</sup> exchanger to reverse its function, which\ntransfers Ca<sup>2+</sup> into cytoplasm and ultimately causes Ca<sup>2+</sup> overload-triggered pyroptosis. Meanwhile, we found that\nbufalin can upregulate PD-L1 in tumor cells. In combination with the\nPD-1 antibody, the delivery system showed a greater performance during\nthe cancer treatment. BCNPs@gel enhances antitumor efficiency, reduces\nsystemic side effects, extends antitumor mechanism of bufalin, and\nprovides new strategies for inducing pyroptosis and calcium overload\nin cancer immunotherapy via Na<sup>+</sup>/K<sup>+</sup>-ATPase inhibitor.\nThis work provides an application model for numerous other traditional\nChinese medicine ingredients.