The photosensitizer (PS) methylene blue (MB) is confined in the close vicinity of an Au nanorod, by incorporating it into SiO2 during Au-core/SiO2-shell nanoparticle (NP) growth. Upon light irradiation of the Au@(SiO2-MB) NPs, generation of reactive oxygen species and their transport to the cytoplasm are directly responsible for significantly decreased cell viability. We have excluded the independent role of the photothermal effect and demonstrated the major role of the plasmonic effect in enhancing drug efficacy using Au@(SiO2-MB) NPs. The “spatial vicinity” required for Au and the PS, and the “energy match” between PS absorption and Au surface plasmon resonance are two critical factors to enable the plasmonic effect, which leads to enhanced drug efficacy.
