Background: Prostate cancer is the major cause of cancer death in men and the androgen receptor (AR) has been shown to play a critical role in the progression of the disease. Our previous reports showed that knocking down the expression of the AR gene using a siRNA-based approach in prostate cancer cells led to apoptotic cell death and xenograft tumor eradication. In this study, we utilized a biodegradable nanoparticle to deliver the therapeutic AR shRNA construct specifically to prostate cancer cells. Materials & methods: The biodegradable nanoparticles were fabricated using a poly(DL-lactic-co-glycolic acid) polymer and the AR shRNA constructs were loaded inside the particles. The surface of the nanoparticles were then conjugated with prostate-specific membrane antigen aptamer A10 for prostate cancer cell-specific targeting. Results: A10-conjugation largely enhanced cellular uptake of nanoparticles in both cell culture- and xenograft-based models. The efficacy of AR shRNA encapsulated in nanoparticles on AR gene silencing was confirmed in PC-3/AR-derived xenografts in nude mice. The therapeutic property of A10-conjugated AR shRNA-loaded nanoparticles was evaluated in xenograft models with different prostate cancer cell lines: 22RV1, LAPC-4 and LNCaP. Upon two injections of the AR shRNA-loaded nanoparticles, rapid tumor regression was observed over 2 weeks. Consistent with previous reports, A10 aptamer conjugation significantly enhanced xenograft tumor regression compared with nonconjugated nanoparticles. Discussion: These data demonstrated that tissue-specific delivery of AR shRNA using a biodegradable nanoparticle approach represents a novel therapy for life-threatening prostate cancers. Original submitted 29 September 2011; Revised submitted 9 January 2012; Published online 14 May 2012