title: Long-term stability of chitosan-based polyplexes.
abstract: OBJECTIVE
  There is a lack of information about the long-term stability of chitosan-based polyplexes although a large amount is known as regards transfection efficiency and physicochemical characteristics. The aim of this work is to study the transfection efficiency and physicochemical properties of chitosan-based polyplexes over time when stored at different temperatures in an acetate-buffer at pH 5.5.
  
  
  METHODS
  Aqueous samples of chitosan-based polyplexes were aged at 4 degrees C, 25 degrees C, and 45 degrees C for up to 1 year. Samples were taken at predetermined time-points and evaluated for in vitro transfection efficiency and physiochemical properties (particle size, zeta potential).
  
  
  RESULTS
  One year of storage at 4 degrees C did not result in any major changes in the properties of the polyplexes. At 25 degrees C there were minor changes in the physicochemical characteristics of the polyplexes, and the in vitro transfection efficiency was reduced at 1 year of storage. Storage at 45 degrees C altered both the in vitro transfection efficiency and the physicochemical properties of the polyplexes after a short time.
  
  
  CONCLUSIONS
  The biological and physicochemical stability of the chitosan-based polyplexes are maintained for 1 year of storage in acetate-buffer at 4 degrees C. The changes in the polyplex characteristics at elevated temperatures may be explained by degradation of both plasmid and chitosan.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, University of Oslo, Oslo, Norway.
authors.forename: Kristine
authors.initials: K
authors.lastname: Romøren
authors.forename: Astrid
authors.initials: A
authors.lastname: Aaberge
authors.forename: Gro
authors.initials: G
authors.lastname: Smistad
authors.forename: Beate J
authors.initials: BJ
authors.lastname: Thu
authors.forename: Oystein
authors.initials: O
authors.lastname: Evensen
mesh_terms: D000818:Animals; D001704:Biopolymers / Q000032:analysis / Q000737:chemistry*; D002347:Carps; D002460:Cell Line; D048271:Chitosan / Q000032:analysis / Q000737:chemistry*; D004355:Drug Stability; D004356:Drug Storage; D013997:Time Factors
chemical_list: D001704:Biopolymers; D048271:Chitosan