title: Development of lyophilized gemini surfactant-based gene delivery systems: influence of lyophilization on the structure, activity and stability of the lipoplexes.
abstract: OBJECTIVE
  Cationic gemini surfactants have been studied as non-viral vectors for gene therapy. Clinical applications of cationic lipid/DNA lipoplexes are restricted by their instability in aqueous formulations. In this work, we investigated the influence of lyophilization on the essential physiochemical properties and in vitro transfection of gemini surfactant-lipoplexes. Additionally, we evaluated the feasibility of lyophilization as a technique for preparing lipoplexes with long term stability.
  
  
  METHODS
  A gemini surfactant [12-7NH-12] and plasmid DNA encoding for interferon-γ were used to prepare gemini surfactant/pDNA [P/G] lipoplexes. Helper lipid DOPE [L] was incorporated in all formulation producing a [P/G/L] system. Sucrose and trehalose were utilized as stabilizing agents. To evaluate the ability of lyophilization to improve the stability of gemini surfactant-based lipoplexes, four lyophilized formulations were stored at 25˚C for three months. The formulations were analyzed at different time-points for physiochemical properties and in vitro transfection.
  
  
  RESULTS
  The results showed that both sucrose and trehalose provided anticipated stabilizing effect. The transfection efficiency of the lipoplexes increased 2-3 fold compared to fresh formulations upon lyophilization. This effect can be attributed to the improvement of DNA compaction and changes in the lipoplex morphology due to the lyophilization/rehydration cycles. The physiochemical properties of the lyophilized formulations were maintained throughout the stability study. All lyophilized formulations showed a significant loss of gene transfection activity after three months of storage. Nevertheless, no significant losses of transfection efficiency were observed for three formulations after two months storage at 25 ˚C.
  
  
  CONCLUSIONS
  Lyophilization significantly improved the physical stability of gemini surfactant-based lipoplexes compared to liquid formulations. As well, lyophilization improved the transfection efficiency of the lipoplexes. The loss of transfection activity upon storage is most probably due to the conformational changes in the supramolecular structure of the lipoplexes as a function of time and temperature rather than to DNA degradation.
authors.affiliation: Drug Design and Discovery Research Group, College of Pharmacy and Nutrition, University of Saskatchewan, 110 Science Place, Saskatoon, Canada.
authors.forename: Waleed
authors.initials: W
authors.lastname: Mohammed-Saeid
authors.forename: Deborah
authors.initials: D
authors.lastname: Michel
authors.forename: Anas
authors.initials: A
authors.lastname: El-Aneed
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Verrall
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Low
authors.forename: Ildiko
authors.initials: I
authors.lastname: Badea
mesh_terms: D000818:Animals; D019556:COS Cells; D002412:Cations / Q000737:chemistry; D002460:Cell Line; D002626:Chemistry, Pharmaceutical / Q000379:methods; D002522:Chlorocebus aethiops; D004247:DNA / Q000008:administration & dosage / Q000737:chemistry* / Q000235:genetics*; D004355:Drug Stability; D004356:Drug Storage; D005079:Excipients / Q000737:chemistry; D005612:Freeze Drying / Q000379:methods*; D018014:Gene Transfer Techniques; D005822:Genetic Vectors / Q000737:chemistry / Q000235:genetics; D007371:Interferon-gamma / Q000737:chemistry; D008055:Lipids / Q000737:chemistry*; D010316:Particle Size; D010957:Plasmids / Q000737:chemistry / Q000235:genetics; D013395:Sucrose / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*; D014162:Transfection / Q000379:methods; D014199:Trehalose / Q000737:chemistry
chemical_list: D002412:Cations; D005079:Excipients; D008055:Lipids; D013501:Surface-Active Agents; D013395:Sucrose; D007371:Interferon-gamma; D004247:DNA; D014199:Trehalose