Gold nanoparticles have unique optical properties such as surface-plasmon and photothermal effects. Such properties have resulted in
gold nanoparticles having several clinical applications.
Gold nanorods (which are rod-shaped
gold nanoparticles) show a surface plasmon band in the near-infrared region. They have therefore been proposed as
contrast agents for bioimaging, or as heating devices for
photothermal therapy.
Polyethylene glycol-modified
gold nanorods systemically administrated into mice can be detected with integrating sphere, and the stability of the
gold nanorods in blood flow evaluated. After
intravenous injection of
gold nanorods followed by near-infrared
laser irradiation, significant
tumor damage triggered by the photothermal effect was observed. To deliver
gold nanorods to the target tissue, thermosensitive
polymer gel-coated
gold nanorods were prepared. After
intravenous injection of the gel-modified
gold nanorods and irradiation of the
tumor, a larger amount of
gold was detected in the irradiated
tumor than in the non-irradiated
tumor. This effect is due to the hydrophobic interaction between the cellular membrane or the extracellular matrix and the gel surfaces induced by the photothermal effect. Furthermore, the photothermal effect enhanced the permeability of the stratum corneum of the skin. As a result of treatment of the skin with
ovalbumin and
gold nanorods followed by near-infrared light irradiation, a significant amount of
protein was detected in the skin. The
gold nanorods therefore showed several functions as a photothermal nanodevice for bioimaging, thermal
therapy, and a drug delivery system.