Gold Nanorods with Silica Shell and PAMAM Dendrimers for Efficient Photothermal Therapy and Low Toxic Codelivery of Anticancer Drug and siRNA

The multifunctional nanocomposites with grafting polyamidoamine dendrimers up to third generation (G(3)) are grown onto the surface of mesoporous silica-coated gold nanorods (AuNRs@SiO2) via a divergent technique. The resultant AuNRs@SiO2-G(3) nanocomposites with uniform size and excellent stability not only enable their utilization as targeted contrast agents for photothermal cancer therapy but also serve as scaffolds for the intracellular delivery of anticancer drug and small interfering RNA (siRNA) to enhance the efficiency of cancer therapy. The controlled doxorubicin (DOX) release from AuNRs@SiO2-G(3) nanocomposites is significantly improved under lower pH condition and near-infrared laser irradiation. The Bcl-2-targeted siRNA is transfected into tumor cells and induces knockdown of the protein expression, which is confirmed by western blot assays. Furthermore, the complementary effect of chemo- and gene therapy to MCF-7 cells for improved photothermal therapy is demonstrated by MTT assay. The DOX and siRNA coloaded AuNRs@SiO2-G(3) nanocomposites show much lower cytotoxicity compared to the DOX, resulting in low toxicity to normal tissues. The multifunctional nanocomposites have potential application as nanoplatforms to integrate the photothermal-chemo-gene tumor therapy with high efficiency.