Purpose: 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.