[Drug Release System Controlled by Photothermal Effect of Gold Nanoparticles].

Controlled drug release in response to light irradiation is an important technique for focusing drug elution to specific sites and reducing the side effects of drugs in normal tissue. In one example, we used double-stranded DNA to modify gold nanorods. When the gold nanorods were heated by irradiation with near-infrared light, single-stranded DNA was released. Thus, we successfully prepared a controlled release system that responds to near-infrared irradiation by combining heat-labile linkers such as double-stranded DNA. However, the drug-loading capacity on the surface of the nanoparticles was limited. To improve the loading efficiency, we encapsulated gold nanorods in poly(lactic-co-glycolic acid) (PLGA) nanoparticles, where PLGA acted as a drug payload. When the gold nanorod-containing PLGA nanoparticles were irradiated with a near-infrared laser, the PLGA nanoparticles were destroyed and significant drug release was observed. In another example, silver nanoplates were used as a near-infrared responsive photothermal nanodevice. Silver nanoparticles show antimicrobial activity that we expected could be controlled by light irradiation. First, we coated the silver nanoplates with gold atoms to mask the antimicrobial activity. When the gold-coated silver nanoplates were irradiated with a near-infrared pulsed laser, the shape of the silver nanoplates changed from plate-like to spherical, and silver ions were released. As a result, the antibacterial activity of the silver nanoplates was recovered. In this review, we outline examples of controlled release systems that respond to light irradiation. We believe that this review will contribute to improving the efficiency and safety of chemotherapy.