CaO2 Nanomedicines: A Review of Their Emerging Roles in Cancer Therapy

Abstract Nanomedicines based on nanoscale metal peroxides have multifunctional properties for cancer theranostics, such as producing bioactive small molecules (e.g., metal ions, H2O2, O2, and OH-). Among various metal peroxides, calcium peroxide (CaO2) nanomedicines are widely studied due to their easy synthesis and biocompatibility. CaO2 nanoparticles can treat cancers through three main mechanisms: (1) producing O2 to alleviate tumor hypoxia and enhance O2-dependent therapies (e.g., chemotherapy, photodynamic therapy, and immunotherapy); (2) generating H2O2, the precursor of ·OH that triggers cancer chemodynamic therapy; and (3) releasing Ca2+ that induces calcium overload and calcification, which impair tumor survival (ion-interference therapy). This review summarizes the recent examples of CaO2 nanoparticle-based cancer therapeutic strategies and discusses the challenges and future directions of CaO2 nanomedicines.