title: Development of a novel method for formulating stable siRNA-loaded lipid particles for in vivo use.
abstract: OBJECTIVE
  A simple yet novel method was developed to prepare stable PEGylated siRNA-loaded lipid particles which are suitable for in vivo use.
  
  
  METHODS
  PEGylated siRNA-loaded lipid particles were formulated by hydration of a freeze-dried matrix. The effect of various formulation parameters on the size and homogeneity of resulting particles was studied. Particles prepared using this method were compared to those prepared using an established post-insertion procedure for the entrapment efficiency, stability, in vitro biological activity as well as in vivo biodistribution.
  
  
  RESULTS
  Using this hydration method, a particle size of less than 200 nm can be obtained with high siRNA entrapment efficiency (>90%) and high gene-silencing efficiency. Following intravenous administration into mice, these particles achieved a similar degree of accumulation in subcutaneous tumours but displayed less liver uptake compared to the post-insertion formulations. Importantly, in contrast to post-insertion preparations, particles made by hydration method retained 100% of their gene-silencing efficiency after storage at room temperature for 1 month.
  
  
  CONCLUSIONS
  This paper describes a simple method of formulating PEGylated siRNA-loaded lipid particles. Given the ease of preparation, long term stability and favourable characteristics for in vivo delivery, our work represents an advance in lipid formulation of siRNA for in vivo use.
authors.affiliation: Diamantina Institute for Cancer, Immunology and Metabolic Medicine, University of Queensland, Princess Alexandra Hospital, Ipswich Rd, Buranda, QLD 4102, Australia.
authors.forename: Sherry Y
authors.initials: SY
authors.lastname: Wu
authors.forename: Lisa N
authors.initials: LN
authors.lastname: Putral
authors.forename: Mingtao
authors.initials: M
authors.lastname: Liang
authors.forename: Hsin-I
authors.initials: HI
authors.lastname: Chang
authors.forename: Nigel M
authors.initials: NM
authors.lastname: Davies
authors.forename: Nigel A J
authors.initials: NA
authors.lastname: McMillan
mesh_terms: D000818:Animals; D004337:Drug Carriers / Q000737:chemistry*; D004339:Drug Compounding; D004355:Drug Stability; D005260:Female; D006367:HeLa Cells; D006801:Humans; D007275:Injections, Intravenous; D008055:Lipids / Q000737:chemistry*; D051379:Mice; D008810:Mice, Inbred C57BL; D009369:Neoplasms / Q000378:metabolism; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D013499:Surface Properties; D013678:Technology, Pharmaceutical / Q000379:methods*; D014018:Tissue Distribution
chemical_list: D004337:Drug Carriers; D008055:Lipids; D034741:RNA, Small Interfering; D011092:Polyethylene Glycols