[Show abstract][Hide abstract] ABSTRACT: Small interfering RNA (siRNA) has tremendous potential as a therapeutic agent for diverse diseases; however, due to its susceptibility to degradation and poor cellular uptake, the low efficiency of administration has been the most important limiting factor for clinical applications of siRNA. Herein, we synthesized alkyl chain modified low-molecular-weight polyethylenimines (LMW PEIs) and found that hydrophobically modified PEIs displayed enhanced efficiency in siRNA-mediated knockdown of target genes. To elucidate the mechanism for increased delivery, we characterized the polymers' physicochemical properties and bioactivity via nuclear magnetic resonance (NMR), gel retardation assay, dynamic laser scattering (DLS) analysis, confocal laser scanning microscopy and flow cytometry. The hydrophobic modification reduced siRNA binding affinity but facilitated the formation of nanoparticles in contrast to the original PEI. The PEIs with eight and thirteen alkyl tails were able to self-assemble into nanoparticles and yielded higher cellular uptake, which leaded to even similar efficiencies of 80-90% knockdown as Lipofectamine™ 2000 control. These results suggested that the status of polymers in aqueous solution, which depended on the degree of hydrophobic modification, played an important role in the uptake of siRNA. Therefore, we provided new information on the role of hydrophobic content in the enhanced gene silencing activity.
No preview · Article · Apr 2013 · International Journal of Pharmaceutics
[Show abstract][Hide abstract] ABSTRACT: A non-viral siRNA carrier composed of mono-methoxy-poly (3-hydroxybutyrate-co-4-hydroxybutyrate)-block-polyethylene glycol-block-linear polyethyleneimine (lPEI, 1800 Da) (mP3/4HB-b-PEG-b-lPEI) was synthesized and evaluated for siRNA delivery. Our study demonstrated that siRNA could be efficiently combined with mP3/4HB-b-PEG-b-lPEI (mAG) copolymer and were protected from nucleases degradation. The combined siRNA were released from the complexes easily under heparin competition. The particle size of mAG/siRNA complexes was 158 nm with ζ-potential around 28 mV and AFM image displayed spherical and homogeneously distributed complexes. The mAG block copolymer displayed low cytotoxicity and efficient cellular uptake of Cy3-siRNA in A549 cells by flow cytometry and confocal microscopy. In vitro transfection efficiency of the block copolymer was assessed by siRNA against luciferase in cultured A549-Luc, HeLa-Luc, HLF-Luc, A375-Luc and MCF-7-Luc cells. A higher transfection efficiency and lower cytotoxicity was obtained by mAG block copolymer in five cell lines. Furthermore, a remarkable improvement in luciferase gene silencing efficiency of mAG complex (up to 90%-95%) in HLF-Luc and A375-Luc cells was observed than that of Lipofectamine(TM) 2000 (70%-82%). Additionally, the mAG/p65-siRNA complex also showed better capability than Lipofectamine(TM) 2000/p65-siRNA complex to drastically reduced p65 mRNA level down to 10%-16% in HeLa, U251 and HUVEC cells at an N/P ratio of 70.
No preview · Article · Jan 2013 · Acta biomaterialia
[Show abstract][Hide abstract] ABSTRACT: A class of non-viral siRNA vectors consisting of biodegradable poly(hydroxyalkanoates) (PHA) grafted onto branched poly(ethyleneimine) (bPEI, 25 kDa) was synthesized and evaluated for siRNA delivery. The mPHA-g-bPEI copolymers were synthesized through Michael addition between acrylated mono-methoxy-poly(hydroxyalkanoates) (mPHA-acrylated) and bPEI with various block length poly(hydroxyalkanoates) from 1300 to 2900 Da. Our research showed that mPHA-g-bPEI copolymers could effectively bind siRNA, protect it from degradation by nucleases and efficiently release the complexed siRNA in the presence of low concentrations of polyanionic heparin. The particle size of mPHA-g-bPEI/siRNA complexes was <200 nm with ζ-potential between 33 and 43 mV. mPHA-g-bPEI copolymers displayed low cytotoxicity compared to unmodified bPEI and efficient cellular uptake of Cy3-siRNA in A549 cells by flow cytometry and confocal microscopy. siRNA delivery efficiency of the copolymers was assessed by siRNA against luciferase in cultured A549-Luc and MCF-7-Luc cells. Those mPHA-g-bPEI copolymers revealed a higher transfection efficiency and lower cytotoxicity than bPEI in two cell lines. Furthermore, a remarkable knockdown of luciferase expression of mPHA-g-bPEI (mAP2) complex (up to 85%) in vitro was found to be equivalent to that of commercially available transfection agent Lipofectamine™ 2000.
[Show abstract][Hide abstract] ABSTRACT: Extensive applications and frequent long-term use of pesticides can affect behavioural mechanisms and physiological and biochemical aspects of insects, leading to resistance. However, insect control strategies involving a different mode of action would be valuable for managing the emergence of insect resistance. In this context, the development of RNA interference technology has brought a turning point in the creation of new biopesticides.
Full-length cDNA of Rieske iron-sulfur protein (RISP) was cloned and characterised from Plutella xylostella L. Three siRNAs specific to RISP sequences were designed and chemically synthesised, and fed to P. xylostella larvae by coating cabbage leaves. This resulted in specific gene silencing of RISP, and consequently brought significant mortality of P. xylostella larvae compared with the control treatment. Silencing of RISP leads to significantly lower transcript levels of RISP compared with the control. In addition, the amount of ATP in the surviving larvae was lower than in the control. However, surviving larvae gradually recovered to normal transcript and protein levels.
This is the first demonstration of the potential use of chemically synthesised siRNA in the development of new biopesticides as a mitochondrial electron transport inhibitor.
No preview · Article · May 2011 · Pest Management Science