Preparation of PEG-modified PAMAM dendrimers having a gold nanorod core and their application to photothermal therapy.

This study was conducted to attempt development of a new type of hybrid dendrimer consisting of a gold nanorod (GNR) core and PEG-modified PAMAM (PEG-PAMAM) dendrons by adding PEG-PAMAM G2-G4 dendrimers with a cystamine core at various timings during the GNR growing reaction. We obtained hybrids of the dendrimers and GNRs exhibiting surface plasmon resonance in the near infrared region. Whereas the PEG-PAMAM G4 dendrimer-GNR hybrid formed an aggregate in an aqueous solution, PEG-PAMAM G2 and G3 dendrimers respectively gave hybrids with average diameters of 24 nm and 31 nm. Especially, the spherical PEG-PAMAM G3 dendrimer-GNR hybrid might be regarded as a GNR-cored PEG-PAMAM dendrimer in which the GNR core was well stabilized by highly hydrated PEG-PAMAM G3 dendrons. The GNR-cored PEG-PAMAM G3 dendrimer exhibited excellent heat-generation capability under near-infrared light irradiation. Incubation with the GNR-cored PEG-PAMAM G3 dendrimer showed no damage to HeLa cells. However, dendrimer-treated cells were killed effectively by near-infrared laser irradiation, indicating excellent photothermal capability of the GNR-cored PEG-PAMAM G3 dendrimer. Furthermore, the GNR-cored PEG-PAMAM G3 dendrimer injected into mice tumor tissues significantly increased the temperature of the tumor when irradiated with near infrared light, resulting in a decreased tumor volume. These results demonstrate that GNR-cored PEG-PAMAM dendrimers might be a new nanomaterial for biomedical applications such as photothermal therapy.