Chitosan-based hybrid nanocomplex for siRNA delivery and its application for cancer therapy.

PURPOSE: Chitosan, a natural and biocompatible cationic polymer, is an attractive carrier for small interfering RNA (siRNA) delivery. The purpose of this study was to develop a chitosan-based hybrid nanocomplex that exhibits enhanced physical stability in the bloodstream compared with conventional chitosan complexes. Hybrid nanocomplexes composed of chitosan, protamine, lecithin, and thiamine pyrophosphate were prepared for systemic delivery of survivin (SVN) siRNA. METHODS: Physicochemical properties of the nanoparticles including mean diameters and zeta potentials were characterized, and target gene silencing and cellular uptake efficiencies of the siRNA nanocomplexes in prostate cancer cells (PC-3 cells) were measured. In vivo tumor targetability and anti-tumor efficacy by systemic administration were assessed in a PC-3 tumor xenograft mouse model by near-infrared fluorescence (NIRF) imaging and tumor growth monitoring, respectively. RESULTS: Mean diameters of the SVN siRNA-loaded hybrid nanocomplex (GP-L-CT) were less than 200 nm with a positive zeta potential value in water and were maintained without aggregation in culture media and 50% fetal bovine serum. SVN expression in PC-3 cells was reduced to 21.9% after treating with GP-L-CT. The tumor targetability and growth inhibitory efficacies of GP-L-CT supported the use of this novel hybrid nanocomplex as a cancer therapeutic and as a theranostic system for systemic administration. CONCLUSIONS: A chitosan-based hybrid nanocomplex was successfully developed for the systemic delivery of SVN siRNA, which could serve as an alternative to cationic polymeric nanoparticles that are unstable in serum.

Enhanced cellular delivery and transfection efficiency of plasmid DNA using positively charged biocompatible colloidal gold nanoparticles.

Efficient and safe nonviral gene delivery systems are a prerequisite for the clinical application of therapeutic genes. In this study, we report an enhancement of the transfection efficiency of plasmid DNA, via the use of positively charged colloidal gold nanoparticles (PGN). Plasmid DNA encoding for murine interleukin-2 (pVAXmIL-2) was complexed with PGN at a variety of ratios. The delivery of pVAXmIL-2 into C2C12 cells was dependent on the complexation ratios between PGN and the plasmid DNA, presented the highest delivery at a ratio of 2400:1. After complexation with DNA, PGN showed significantly higher cellular delivery and transfection efficiency than did the polyethylenimines (PEI) of different molecular weights, such as PEI25K (m.w. 25 kd) and PEI2K (m.w. 2 kd). PGN resulted in a cellular delivery of pVAXmIL-2 6.3-fold higher than was seen with PEI25K. The PGN/DNA complex resulted in 3.2- and 2.1-fold higher murine IL-2 protein expression than was seen in association with the PEI25K/DNA and PEI2K/DNA complexes, respectively. Following intramuscular administration, PGN/DNA complexes showed more than 4 orders of magnitude higher expression levels as compared to naked DNA. Moreover, the PGN/DNA complexes showed higher cell viability than other cationic nonviral vectors. Collectively, the results of this study suggest that the PGN/DNA complexes may harbor the potential for development into efficient and safe gene delivery vehicles.

Tocopheryl oligochitosan-based self assembling oligomersomes for siRNA delivery.

Amphiphilic α-tocopherol oligochitosan conjugates were constructed by conjugating α-tocopherol succinate to water soluble oligochitosans with various molecular weights. In aqueous medium, the tocopherol oligochitosan conjugates self-assembled to single layered oligomersomes. The sizes of α-tocopherol-oligochitosan-based oligomersomes (TCOsomes) could be controlled by chain lengths of oligochitosans. The mean sizes of TCOsomes were 220 and 377 nm as the sizes of oligochitosans were 4000 and 12,500, respectively. For all TCOsomes formed in this study, polydispersity indexes were in the ranges of 0.111-0.256. Cryo-TEM images showed clear thickening in the unilamellar layer of TCOsomes upon complexation with siRNAs. Zeta potentials decreased as the ratios of siRNA/TCOsomes increased. TCOsomes self-assembled from tocopherol-oligochitosan 4K (TCOsome(4K)) significantly enhanced the cellular uptake of siRNAs (>98%), and reduced the expression of target proteins more effectively than did Lipofectamine 2000. In tumor xenografted mice, the intratumoral administration of siMcl-1 using TCOsomes substantially silenced the expression of Mcl-1 and prevented the growth of tumor. The hematoxylin-eosin staining showed the apoptosis of cells in the tissues of the mice treated with siMcl-1/TCOsome(4K) complexes, but not with siGL2/TCOsome(4K) complexes. The self-assembling and size-controllable oligomersomes might be suitable for effective in vivo delivery of siRNAs.

Pegylated poly-l-arginine derivatives of chitosan for effective delivery of siRNA.

For delivery of siRNA, chitosan (CS) was derivatized with poly-l-arginine (PLR) and polyethylene glycol (PEG). The formation of polyplexes with siRNA was confirmed by gel retardation. The PLR-grafted CS formed nanosized particles with siRNA. PLR-grafted CS showed higher cellular delivery efficiency of siRNA than did CS, pegylated CS, PLR, or pegylated PLR. The extent of reduction in the expression of fluorescent proteins was highest following treatment of the cells using PLR derivatives of CS in complexes with specific siRNAs. Cell viability was greater in populations treated with pegylated CS-PLR than in those treated with PLR. Hemolysis of erythrocytes was reduced upon conjugation of PLR with CS. The delivery of siRNAs via pegylated CS-PLR revealed little dependence on serum. Molecular imaging techniques revealed that the intratumoral administration of red fluorescent protein-specific siRNA in complexes with pegylated CS-PLR significantly silenced the expression of red fluorescent proteins in tumor tissues in vivo. These results indicate that pegylated CS-PLR might be useful for in vivo delivery of therapeutic siRNAs.