Small interfering RNA (siRNA) has recently illustrated therapeutic potential for malignant disorders. However,
the clinical application of siRNA-based therapeutics is significantly retarded by the paucity of successful delivery
systems. Recently, multifunctional gold nanoparticles (AuNPs) as non-viral delivery carriers have shown promise
for transporting chemotherapeutics, proteins/peptides, and genes. In this study, AuNPs capped with polyethylenimine (PEI) and PEGylated anisamide (a ligand known to target the sigma receptor) have been developed
to produce a range of positively charged anisamide-targeted PEGylated AuNPs (namely Au-PEI-PEG-AA). The
anisamide-targeted AuNPs effectively complexed siRNA via electrostatic interaction, and the resultant complex
(Au110-PEI-PEG5000-AA.siRNA) illustrated favourable physicochemical characteristics, including particle size,
surface charge, and stability. In vitro, anisamide-targeted AuNPs selectively bound to human prostate cancer PC3 cells, inducing efficient endosomal escape of siRNA, and effective downregulation of the RelA gene. In vivo, prolonged systemic exposure of siRNA was achieved by anisamide-targeted AuNPs resulting in significant tumour growth suppression in a PC3 xenograft mouse model without an increase in toxicity. In addition, a
combination of siRNA-mediated NF-κB knockdown using anisamide-targeted AuNPs with Paclitaxel produced a
synergistic therapeutic response, thus providing a promising therapeutic strategy for the treatment of prostate
cancer.