# Gold Nanoparticles for Drug Delivery and Cancer Therapy
## 4 Gold Nanoparticle-Based Drug Delivery
### Ribonucleic Acids (RNAs) Delivery  
The use of RNA macromolecules as therapeutic agents for HIV, delivered directly to the target site, shows promising results. Lymphocytes that are in the body are particularly difficult to transfect. Therefore, an RNA delivery system carried in Au NPs was designed to carry out the task. A PEGylated Au NP scaffold covalently connected to thiol-modified oligoribonucleotide through a cleavable N-succinimidyl 3-(2-puridyldithio) propionate (SPDP) linker molecule was used. Cationic polymer polyethyleneimine was used to coat the Au NPs to enhance cell entry and endosomal escape. A synthetic anti-CD4 cyclic targeting peptide was linked to the Au NPs via SPDP linker molecule, which enhanced the uptake and selectivity of speared non-target cells. Approximately 45,000 RNA strands were uptaken per lymphocyte. No antiviral activity was detected, so it is a promising solution in the HIV treatment [85]. In gene and cancer therapy, RNA interference mediated gene silencing show potential. A hairpin RNA delivery system was introduced where a functionalized Au nanorod effectively condenses small hairpin RNA into stable NP. This can efficiently target specific points of human brain cancer cells. The combination effect of endosomal escape and the efficient cleavage of the disulfide-cross-linked short polyethylenimines by the high intracellular glutathione content triggers rapid cytoplasma RNA release, which produces excellent RNA interference efficiency and low cytotoxicity. High stability and prolonged blood circulation was obtained by PEGylation, which allowed for the effective accumulation of carriers in targeted tumors, resulting in outstanding intra-tumor gene silencing efficiency in brain cells, and the theory was tested on tumor-bearing mice and showed promising results [86]. In glioblastoma, delivering appropriate drug concentrations to the brain is very challenging. A new method has been proposed that explores the potential of a nose-to-brain direct transport pathway to bypass the blood brain barrier. This idea utilizes the delivery of targeted theranostic polyfunctional gold-iron oxide NP surface loaded with therapeutic micro RNA to glioblastoma. This carrier can deliver chemotherapy drug temozolomide. The drug has been tested on mice and shows promising results and potential for clinical use [87]. Triple negative breast cancer patients generally have worse clinical outcomes due to the high rate of recurrence. A new method for treating this cancer was proposed where multilayered NPs carrying metastasis suppressor microRNA (miRR780) are localized to the target cancer area. The efficient delivery of the RNA could reduce lung metastasis. In vivo studies of this approach show promising outcomes and potential in triple negative breast cancer [88]. For the treatment of ovarian cancer, Au NPs can be used to deliver DNA to the target site. The study also looks at the anticancer effect of DOX-DNA-Au NP on three ovarian cancer cell lines, namely, SK-OV-3, HEY A8, and A2780 using EZ-Cytox cell viability assay. The result shows that Dox-DNA-Au NP gives outstanding activity and can be a viable option for the cancer treatment [89].