Targeted Delivery of siRNA to the Tumor

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Last Modified
  • March 20, 2019
Creator
  • Li, Shyh-Dar
    • Affiliation: Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics
Abstract
  • We have developed a surface-modified LPD (liposome-polycation-DNA) nanoparticle formulation by mixing cationic liposomes, a polycationic peptide and nucleic acids (mixture of DNA and siRNA) at a fixed ratio, followed by post-inserting a PEGylated lipid. This self-assembled nanoparticle formulation was around 100 nm in diameter with 90% encapsulation efficiency for siRNA. The nucleic acid was complexed with the peptide into a compact core, which was coated with two lipid bilayers. The inner lipid bilayer was stabilized by the charge-charge interaction between the cationic lipids and the compact core. Upon addition of a PEGylated lipid, the outer lipid bilayer was stripped off and the lipid anchor was inserted into the outer leaflet of the inner bilayer, resulting in approximately 10.6 mol% modification of PEG (polyethylene glycol) on the surface of the nanoparticles. The high degree of PEGylation completely shielded the charge of the nanoparticles with the zeta potential close to neutral (-5.6 ± 4.5 mV) and abolished the reticuloendothelial uptake in the isolated liver. When i.v. injected into tumor bearing mice (s.c. human lung cancer xenograft model in the nude mice), the nanoparticles delivered 70-80% injected siRNA/g into the tumor, while the normal organs only showed a moderate uptake (10-20% injected siRNA/g). After the conjugation of a targeting ligand, anisamide, at the distal end of the PEG, the intracellular delivery of siRNA into the sigma receptor expressing tumor was significantly enhanced. This led to efficient EGFR silencing, significant apoptosis induction and tumor growth inhibition at the dose of 1.2 mg siRNA/kg for three consecutive injections. The experimental murine lung metastasis model was established by i.v. injecting the mouse melanoma cells, which were stably transduced with a luciferase gene by retrovirus, into the mice. An improved metastatic tumor delivery of siRNA was discovered by using the nanoparticles. When combinatorial siRNA sequences were delivered, the oncogenes (MDM2, c-myc and VEGF) in the lung metastasis were silenced simultaneously, leading to 70-80% tumor load reduction and 30% prolongation in animal lifespan. The nanoparticle formulation showed minimal to no otoxicity in both animal models. The results promise the potential use of this formulation clinically.
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  • In Copyright
Advisor
  • Huang, Leaf
  • Cho, Moo J.
  • Blancafort, Pilar
  • Xiao, Xiao
  • Mumper, Russell J.
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2008
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  • This item is restricted from public view for 2 years after publication.
Date uploaded
  • April 26, 2017

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