(547d) Responsive and Targeted Nanoparticles for Intracellular Delivery

We develop a method for prostate-specific small interfering RNA (siRNA) delivery using responsive nanoparticles by functionalization of poly (lactic-co-glycolic acid) (PLGA) and poly (ethylene glycol) (PEG) based copolymer. Here we demonstrate the successful siRNA packaging, targeting and cytoplasm delivery of siRNA into two prostate cancer cell lines: LNCaP and 22RV1. The new delivery system shows the potential to regulate the androgen receptor protein to improve prostate cancer treatment.

Specifically, we chemically modify the PLGA-PEG diblock copolymer backbone to overcome the low siRNA encapsulation ability caused by the hydrophobic nature of PLGA. The PLGA-PEG diblock copolymer is further modified by adding functionalities for preferential escape from the endosome. These chemical modifications eventually lead to the efficient nanoparticle release into the cytoplasm. The nanoparticles are further surface functionalized by conjugation with A10 aptamer, which improves cell uptake via endocytosis by targeting prostate specific membrane antigen on both LNCaP and 22RV1 prostate cancer cells. The siRNA-nanoparticle endosomal escape is visualized by confocal fluorescent microscopy. To assess siRNA delivery efficiency, protein assays were used to demonstrate a decrease in protein expression consistent with activation of the RNAi pathway. In the case of the model GAPDH gene, the KDalert GAPDH assay shows the decrease of GAPDH protein levels. This result is further confirmed by Western blots, which show the decrease of the androgen receptor protein levels relative to loading control. Concurrently, real time PCR using TaqMan Gene Expression Assay probes relevant for the target gene shows relative lower amount of target mRNA relative to beta-actin in the treated cell populations.

Our results demonstrate that the new targeted and responsive PLGA-PEG based nanoparticles are efficient carrier for siRNA delivery and gene silencing in prostate cancer, which may result in favorable development of clinically relevant targeted therapies.