Gold nanorods have strong absorption bands in the near-infrared region, in which light penetrates deeply into tissues. The absorbed light energy is converted into heat by gold nanorods, the so-called 'photothermal effect'. Hence, gold nanorods are expected to act not only as on-demand thermal converters for photothermal therapy but also as controllers of a drug-release system responding to irradiation by near-infrared light. To achieve a controlled-release system that can be triggered by light irradiation, double-stranded DNA (dsDNA) was modified on gold nanorods. When the dsDNA-modified gold nanorods were irradiated by near-infrared light, the single-stranded DNA (ssDNA) was released from gold nanorods due to the photothermal effect. The amount of released ssDNA was dependent upon the power and exposure time of light irradiation. Release of ssDNA was also observed in tumors grown on mice after light irradiation. Such a controlled-release system of oligonucleotide triggered by the photothermal effect could expand the applications of gold nanorods that have unique optical characteristics in medicinal fields.
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