title: Novel RGD-lipid conjugate-modified liposomes for enhancing siRNA delivery in human retinal pigment epithelial cells.
abstract: BACKGROUND
  Human retinal pigment epithelial cells are promising target sites for small interfering RNA (siRNA) that might be used for the prevention and/or treatment of choroidal neovascularization by inhibiting the expression of angiogenic factor; for example, by downregulating expression of the vascular endothelial growth factor gene.
  
  
  METHODS
  A novel functional lipid, DSPE-PEG-RGD, a Arg(R)-Gly(G)-Asp(D) motif peptide conjugated to 1, 2-distearoyl-sn-glycero-3-phosphoethanolamine- N-[maleimide (polyethylene glycol)-2000], was synthesized for the preparation of siRNA-loaded RGD-PEGylated liposomes to enhance uptake of encapsulated siRNA in retinal pigment epithelial cells. Various liposomes, with 1 mol% and 5 mol% PEGylated lipid or 1 mol% and 5 mol% RGD-PEGylated lipid, were fabricated.
  
  
  RESULTS
  Characterization of the liposomes, including siRNA entrapment efficiency, average particle size and ζ-potential, were determined to be as follows: >96%, 129.7 ± 51 to 230.7 ± 60.7 nm, and 17.3 ± 0.6 to 32 ± 1.3 mV, respectively. For the in vitro retinal pigment epithelial cell studies, the RGD-PEGylated liposomes had high delivery efficiency with siRNA delivery, about a four-fold increase compared with the PEGylated liposomes. Comparison of the various liposomes showed that the 1 mol% RGD-modified liposome had less cytotoxicity and higher siRNA delivery efficiency than the other liposomes. The antibody blocking assay confirmed that uptake of the 1 mol% RGD-PEGylated liposome was via integrin receptor- mediated endocytosis in retinal pigment epithelial cells.
  
  
  CONCLUSIONS
  The results of this study suggest that RGD-PEGylated liposomes might be useful for siRNA delivery into retinal pigment epithelial cells by integrin receptor-medicated endocytosis.
authors: Graduate Institute of Life Sciences, National Defense Medical Center, Neihu, Taipei, Taiwan.
authors: Cheng-Wei
authors: CW
authors: Chen
authors: Da-Wen
authors: DW
authors: Lu
authors: Ming-Kung
authors: MK
authors: Yeh
authors: Chia-Yang
authors: CY
authors: Shiau
authors: Chiao-Hsi
authors: CH
authors: Chiang
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004705:Endocytosis / Q000187:drug effects; D006651:Histocytochemistry; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008081:Liposomes / Q000008:administration & dosage / Q000737:chemistry* / Q000493:pharmacokinetics; D008856:Microscopy, Fluorescence; D009842:Oligopeptides / Q000008:administration & dosage / Q000737:chemistry* / Q000493:pharmacokinetics; D010316:Particle Size; D010714:Phosphatidylethanolamines / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics; D011092:Polyethylene Glycols / Q000737:chemistry; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000737:chemistry* / Q000493:pharmacokinetics; D055213:Retinal Pigment Epithelium / Q000378:metabolism*
chemical_list: D039302:Integrin alphaVbeta3; D008081:Liposomes; D009842:Oligopeptides; D010714:Phosphatidylethanolamines; D034741:RNA, Small Interfering; C038089:1,2-distearoylphosphatidylethanolamine; D011092:Polyethylene Glycols; C047981:arginyl-glycyl-aspartic acid