Dendrimer-Modified Gold Nanorods as High Efficient Controlled Gene Delivery Release System under Near-Infrared Light Irradiation

Gold nanorod-based gene delivery system potentially represents a powerful nanotechnology for cancer therapy. Here we for the first time reported the use of polyamidoamine (PAMAM) dendrimer modified-gold nanorods (dGNR) as a high efficient gene delivery system for the targeted silencing of survivin via RNA interference for breast cancer therapy. Gold nanorods were functionalized with thiol-terminated polyamidoamine dendrimer; survivin shRNA plasmid was constructed and conjugated with dGNR. The resultant survivin-shRNA-GNR nanocomposites were incubated with human breast cancer MCF-7 cells, irradiated with 140 mJ/pulse of laser light of 1,064 nm for 15 s, and then continued to culture for 1 to 3 days. These cells were collected and analyzed by MTT, quantitative reverse transcription-PCR, Western blotting, fluorescent microscopy, and high-resolution transmission electron microscopy. 25 nude mice models with breast cancer were established; the nanocomposites of survivin-shRNA-dGNR were injected into the tumor tissues at gradually increased dose, and then were irradiated with 140 mJ/pulse of laser light of 1,064 nm for 15 s one time per week. The nude mice were raised for two months, and then were sacrificed. The tumor tissues were picked out, and their sizes were measured. Results showed that PAMAM dendrimer-functionalized gold nanorods were successfully synthesized; they could enter into MCF-7 cells within 30 min, release survivin shRNA plasmids with high efficiency, enhance the expression of transferred survivin genes in tumor cells under near-IR laser irradiation, and cause remarkable down-regulation of survivin gene and protein, inhibite cell growth in dose-and time-dependent means, and induce cell apoptosis. EGFP fluorescent signals in the tumor localization of nude mice. The tumor sizes in nude mice became smaller and smaller as the dose of the injected nanocomposites increased. In conclusion, PAMAM dendrimer-functionalized gold nanorods may be a high efficient gene delivery release system for survivin-shRNA vector under near-infrared light irradiation; the constructed survivin-shRNA-dGNR composites can effectively inhibit the growth of breast cancer cells, and have potential applications in breast cancer therapy and molecular imaging.