Gold Nanoparticles\nfor Photothermal and Photodynamic\nTherapy

Cancer cells exposed to 13 nm gold nanoparticles and\nirradiated\nwith cw laser light at 532 nm are shown to undergo cell death via\ntwo competing causes. When cells contain relatively high quantities\nof gold nanoparticles and/or receive a high dose of light, photothermal\neffects dominate, which are independent of the cellular location of\nthe gold nanoparticles and affect all cells in the irradiated area\ndue to the rapid diffusion of heat. In contrast, at lower doses of\nnanoparticles and light, the photogeneration of singlet oxygen triggers\ncell death only in cells that contain a sufficient number of nanoparticles.\nThe parallel occurrence of both effects will need to be considered\ncarefully when designing practical therapy applications. In particular,\nthe photodynamic effect should allow for a cell-type-specific treatment\nmodality that can distinguish between cancer and normal cells using\nsuitable targeting ligands on the nanoparticle surface, providing\na highly selective route for cancer therapy.