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Name (Title):
Atsushi Tamura (Graduate student) 1 , Motoi Oishi (Assistant Professor) 1,2 ,
Yukio Nagasaki (Professor) 1,2,3
Affiliation: 1 Graduate School of Pure and Applied Sciences, University of
Tsukuba, 2 Tsukuba Research Center for Interdisciplinary Materials Science
(TIMS), University of Tsukuba, 3 International Center for Materials
Nanoarchitectonics Satellite (MANA), National Institute of Materials
Science (NIMS) and University of Tsukuba
Email: s-tamura@ims.tsukuba.ac.jp
Home Page: http://www.ims.tsukuba.ac.jp/~nagasaki_lab/index.htm
Presentation Title:
Cytoplasmic Delivery of siRNA Based on the Polyion Complex with Cross-Linked Polyamine
Nanogels Directed to Enhance the Gene Silencing Efficiency
Abstract:
RNA interference (RNAi) is a sequence
specific posttranscriptional gene silencing
pathway initiated by double strand small
interfering RNA (siRNA) with 19 to 23
nucleotide base pairs, which induces
endonucleolytic cleavage of complementary
target mRNA. This powerful gene
regulating method has a tremendous
therapeutic potential on treating various
intractable diseases including genetic
disorders and cancer. Nevertheless, the
Poster Session PB-9
Figure 1. Schematic illustration of cross-linked polyamine
nanogel and siRNA polyion complex.
naked siRNAs exhibit very low gene silencing efficiency in vitro and in vivo due to their poor
intracellular uptake, low stability against enzymatic degradation in blood stream, and rapid
clearance from renal glomeruli via systemic administration. To improve the efficiency of siRNA in
both in vitro and in vivo, hydrophilic poly(ethylene glycol) (PEG)-polyamine block or graft
copolymers were used for complexation with nucleic acid to form nano-sized PEGylated polyplexes
composed of segregated polyion complex core surrounded by PEG palisade layers to increase
biocompatibility and enzymatic tolerability. However, electrostatic interaction between siRNA and
polyamine seems to be weak under extremely dilute conditions and high ionic strength conditions,
because of the short base pairs of siRNA. In this study, PEGylated polyamine nanogels composed
of nano-sized cross-linked poly(N,N-diethylaminoethyl)- methacrylate (PEAMA) gel and
surrounding PEG palisade layers were evaluated as a new class of siRNA carrier to develop the
PEGylated polyplex system (Figure 1). The cross-linked polyamine gel does not undergo
dissociation and cleavage under the physiological condition, suggesting the PEGylated polyamine
nanogel is potential siRNA carrier for the clinical use of siRNAs by systemic administration.
Indeed, the nanogel/siRNA complex showed higher stability against polyanion exchange reaction
than that of PEG-b-PEAMA/siRNA complex. Thus, the nanogel/siRNA complex promoted the
cellular uptake of siRNA to HuH-7 (human hepatocarcinoma) cells compared with that of PEG-b-
PEAMA/siRNA complex and naked siRNA, as determined by flow cytometry. Additionally, in vitro
transfection study revealed that the specific gene silencing activities (RNAi activities) of siRNA
were remarkably enhanced by nanogels/siRNA complexes compared with PEG-b-PEAMA/siRNA
complexes. Therefore, the PEGylated polyamine nanogels would be utilized as a potential siRNA
carrier for in vivo therapeutic application.
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