Stabilization of polymer-based gene delivery systems

To preserve the size and transfection potential of polymer–plasmid complexes, freeze-drying and freeze-thawing were used for stabilization of these complexes. The concentration of the sugars is an important factor affecting both the size and transfection capability of the complexes after freeze-drying and freeze-thawing. However, the type of lyoprotectant (sugar) used is of minor importance. It is also shown that when damage to polymer–plasmid complexes occurs, it results from the drying process but is not due to the freezing step.