Cu-Ferrocene-Functionalized CaO2 Nanoparticles to Enable Tumor-Specific Synergistic Therapy with GSH Depletion and Calcium Overload.

The conversion of endogenous H2 O2 into toxic hydroxyl radical (• OH) via catalytic nanoparticles is explored for tumor therapy and received considerable success. The intrinsic characteristics of microenvironment in tumor cells, such as limited H2 O2 and overexpressed glutathione (GSH), hinder the intracellular • OH accumulation and thus weaken therapeutic efficacy considerably. In this study, fine CaO2 nanoparticles with Cu-ferrocene molecules at the surface (CaO2 /Cu-ferrocene) are successfully designed and synthesized. Under an acidic condition, the particles release Ca2+ ions and H2 O2 in a rapid fashion, while they can remain stable in neutral. In addition, agitated production of • OH occurs following the Fenton reaction of H2 O2 and ferrocene molecules, and GSH is consumed by Cu2+ ions to avoid the potential • OH consumption. More interestingly, in addition to the exogenous Ca2+ released by the particles, the enhanced • OH production facilitates intracellular calcium accumulation by regulating Ca2+ channels and pumps of tumor cells. It turns out that promoted • OH induction and intracellular calcium overload enable significant in vitro and in vivo antitumor phenomena.