Abstract: Provides is a therapeutic technology that combines the phototoxic and immune-stimulating ability of photodynamic therapy with the widespread effectiveness of the immune system to reduce the viability of such as cancer cells and tumors. The nanoparticle compositions of the disclosure combine an immunostimulant with a photosensitizer using a nanoparticle delivery platform. For example, zinc pthalocyanine, which is a long-wavelength absorbing photosensitizer, integrated into a polymeric nanoparticle core made up of poly(D,L-lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-b-PEG). The outside surface of the core can be coated with metallic nanoparticles, which are then modified with CpG-ODN. Metastatic mouse breast carcinoma cells showed significant photocytotoxicity of the hybrid after irradiation with a 660 nm LASER light and this activity was remarkably better than either treatment alone.