Design of a Novel PEGylated Liposomal Vector for Systemic Delivery of siRNA to Solid Tumors

Abstract

A small interfering RNA (siRNA) delivery system using dioleylphosphate-diethylenetriamine conjugate (DOP-DETA)-based liposomes (DL) was assessed for systemic delivery of siRNA to tumors. DL carrying siRNA capable of inducing efficient gene silencing with low doses of siRNA were modified with polyethylene glycol (PEG-DL/siRNA) for systemic injection of siRNA. The biodistribution of DL and siRNA in the PEG-DL/siRNA was studied by using radiolabeled DL and fluorescence-labeled siRNA, respectively. DL in the PEG-DL/siRNA showed a high retention in the plasma, accumulation in the tumor, and low accumulation in the liver and spleen after intravenous injection. The in vivo effects of PEGylation were observed only when distearoylphosphatidylethanolamine (DSPE)-PEG but not distearoylglycerol (DSG)-PEG were used. This result suggests that the electrostatic interaction between lipid molecules on the surface of PEG-DL/siRNA was a critical determinant for the in vivo effect of PEGylation. When PEG-DL/siRNA (0.1 mg/kg siRNA) was intravenously injected into tumor-bearing mice, in vivo gene silencing was observed in subcutaneous tumors. These results indicate that PEG-DL/siRNA designed in this study is a promising formulation for systemic use of siRNA.

Effects of PEG anchors in PEGylated siRNA lipoplexes on in�vitro gene‑silencing effects and siRNA biodistribution in mice

“…in particular, PeG-cS coating of sirna lipoplexes did not inhibit gene-silencing effects by sirna lipoplexes regardless of the cationic lipid type, suggesting that PeG coating via electrostatic interaction may be easily detached from sirna lipoplexes compared with those by incorporation of PeG-lipid derivatives into the liposomal membrane via a lipid anchor. regarding the PeG-dSPe, the electrostatic interaction between the phosphate group of PeG-dSPe and amine group of cationic lipids can remain stably on the surface of sirna lipoplexes (10). From these results, the inhibition of the gene-silencing effects by PeGylation was largely affected by the anchor of PeG derivatives in PeGylated sirna lipoplexes.…”

“…inclusion of PeG-lipid with longer saturated diacyl chains into sirna lipoplexes increased the plasma concentration of lipoplexes after intravenous injection (9), indicated that the length and saturation of the acyl chain in PeG-lipid derivatives strongly affected the stability of PeGylated sirna lipoplexes in the blood circulation after intravenous injection. PeGylated sirna lipoplexes with PeG-dSPe showed excellent blood circulation compared with those incorporating PeG-dMG (10). in addition, PeG-dMG dissociated rapidly from PeGylated lipid nanoparticle-encapsulated sirna, but PeG-dSG dissociated slowly (11).…”

Recent advances in siRNA delivery mediated by lipid-based nanoparticles

“…We previously showed in mice that long circulation of siRNA-loaded pH-sensitive liposomes modified with PEG was observed only when DSPE-PEG but not distearoylglycerol (DSG)-PEG was used. Our results suggest that the electrostatic interaction between lipid molecules on the surface of the liposomes is a critical determinant for the in vivo effect of PEGylation [ 115 ].…”

Environment‐Responsive Lipid/siRNA Nanoparticles for Cancer Therapy

“…[ 117 ] A high density of the amino groups in the lipid could facilitate endosomal escape through the proton‐sponge effect and mediate substantial knockdown of target mRNA. [ 118 ] The knockdown efficiency of DCP‐TEPA liposome/siRNA complexes was determined by the amine to phosphate ratio (N/P ratio), as shown by in vitro experiments where DCP‐TEPA polycation liposomes were complexed with GFP‐labelled siRNA in HT1080 human fibrosarcoma cells. However, PEGylation of the DCP‐TEPA/siRNA complexes caused dissociation of siRNA.…”

“…Dioleylphosphate‐diethylenetriamine (DOP‐DETA) with two ionizable amino groups was developed from a triamine to aid in siRNA encapsulation and to facilitate lipid‐cell membrane interaction as well as lipid‐endosome interaction. [ 118 ] DOP‐DETA with unsaturated oleyl tails contributes to higher membrane fluidity and induced membrane fusion. [ 118 ] DOP‐DETA was formulated with DPPC/cholesterol and siGFP in LNPs that produced high knockdown efficiency in HT1080‐EGFP human fibrosarcoma cells.…”