Bioreducible poly (β-amino esters)/shRNA complex nanoparticles for efficient RNA delivery.

RNA interference (RNAi) mediating gene silencing is a promising approach in the area of gene therapy, but it still is a major challenge to find new non-viral vectors with high transfection efficiency and low toxicity until today. In this work, three novel bioreducible poly (β-amine esters) (PAEs) with different amino monomers in the main chain were designed and synthesized by Michael addition polymerization. All PAEs could condense shRNA into complex nanoparticles with particle size (60-200nm) and positive surface charges (>+10mV). The PAEs/shRNA complex nanoparticles (PAENs) were stable under the extracellular physiological condition, while it would degrade in the reductive environment due to the cleavage of the disulfide bonds in the PAEs main chain. PAENs could achieve efficient cellular uptake and EGFP silencing in HEK-293 cells and U-87 MG cells with low cytotoxicity. The high accumulation of PAENs in tumor and high silencing efficiency of intra-tumor EGFP expression occurred when PAENs were intravenously injected into BALB/c mice bearing U-87 MG-GFP tumor. The relationship between the polymer structure and RNAi efficiency and cytotoxicity showed that the density of nitrogen atoms in PAEs backbone and the existence of disulfide bonds demonstrated the remarkable influence on in vitro and in vivo gene silencing efficiency and cytotoxicity. These experimental results suggested that the PAENs could be a promising non-viral vector for efficient RNA delivery.