Rolling circle transcription-based polymeric siRNA nanoparticles for tumor-targeted delivery.

RNA, one of the major biological macromolecules, has been considered as an attractive building material for bottom-up fabrication of nanostructures in the past few decades due to advancements in RNA biology, RNA chemistry and RNA nanotechnology. Most recently, an isothermal enzymatic nucleic acid amplification method termed rolling circle transcription (RCT), which achieves a large-scale synthesis of RNA nanostructures, has emerged as one of fascinating techniques for RNAi-based therapies. Herein, we proposed a newly designed RCT method for synthesis of polymeric siRNA nanoflower, referred to 'RCT and annealing-generated polymeric siRNA (RAPSI)': (1) Amplification of the antisense strand of siRNA via RCT process and (2) annealing of chimeric sense strand containing 3'-terminal DNA nucleotides that provide enzyme cleavage sites. To verify its potentials in RNAi-based cancer therapy, the newly designed RAPSI nanoflower was further complexed with glycol chitosan (GC) derivatives, and systemically delivered to PC-3 xenograft tumors. The resultant RAPSI nanoparticles exhibited the improved particle stability against polyanion competition or nuclease attack. When the RAPSI nanoparticles reached to the cytoplasmic region, active mono siRNA was liberated and significantly down-regulated the expression of target VEGF gene in PC-3 cells. Excellent tumor-homing efficacy and anti-tumor effects of the RAPSI nanoparticles were further demonstrated. Overall, the proposed RCT-based polymeric siRNA nanoflower formulation can provide a new platform technology that allows further functional modifications via an advanced annealing method for systemic cancer RNAi therapy.

Reducible Polyethylenimine Nanoparticles for Efficient siRNA Delivery in Corneal Neovascularization Therapy.

The aim of this study is to establish the safe and effective ocular delivery system of therapeutic small interfering RNA (siRNA) in corneal neovascularization therapy. The major hurdle present in siRNA-based corneal neovascularization (CNV) therapy is severe cytotoxicity caused by repetitive drug treatment. A reducible branched polyethylenimine (rBPEI)-based nanoparticle (NP) system is utilized as a new siRNA carrier as a hope for CNV therapy. The thiolated BPEI is readily self-crosslinked in mild conditions to make high molecular weight rBPEI thus allowing the creation of stable siRNA/rBPEI nanoparticles (siRNA-rBPEI-NPs). In the therapeutic region, the rBPEI polymeric matrix is effectively degraded into nontoxic LMW BPEI inside the reductive cytosol causing the rapid release of the encapsulated siRNA into the cytosol to carry out its function. The fluorescent-labeled siRNA-rBPEI-NPs can release siRNA into the entire corneal region after subconjuctival injection into the eye of Sprague Dawley rats thus confirming the proof of concept of this system.