Near-Infrared Light Irradiation of Porphyrin-Modified Gold Nanoparticles Promotes Cancer-Cell-Specific Cytotoxicity

The use of nanoparticles has been investigated as a new cancer treatment. These can induce specific cytotoxicity in cancer cells. In particular, Au nanoparticles (AuNPs) have unique characteristics. The maximum absorption spectrum of AuNPs can be adjusted to modify their size or shape to absorb near-infrared light that can penetrate into tissue without photodamage. Thus, the combination of AuNPs and near-infrared light can be used to treat cancer in deep-seated organs. To obtain effective cancer-specific accumulation of AuNPs, we focused on porphyrin and synthesized a porphyrin-attached Au compound: Au-HpD. In this study, we investigated whether Au-HpD possesses cancer-specific accumulation and cytotoxicity. Intracellular Au-HpD accumulation was higher in cancer cells than in normal cells. In order to analyze the cytotoxicity induced by Au-HpD, cancer cells and normal cells were co-cultured in the presence of Au-HpD; then, they were subjected to 870 nm laser irradiation. We observed that, after laser irradiation, cancer cells showed significant morphological changes, such as chromatin condensation and nuclear fragmentation indicative of cell apoptosis. This strong effect was not observed when normal cells were irradiated. Moreover, cancer cells underwent cell apoptosis with combination therapy.