Protecting Effect of Excipients in Freeze-Drying Liposomes Prepared by Ethanol-Injection

The production methods of liposomes is moving from the traditional techniques to the microfluidic and continuous crossflow injection approaches. These techniques allow to obtain quickly unilamellar vesicles avoiding the downsizing step, but require the use of a solvent, generally ethanol, that is usually removed. Lyophilization of these liposome dispersions would avoid this step, increasing concomitantly the shelf-life of the product. Nevertheless, the sublimation of ethanol, which does not freeze completely, may affect the quality of the freeze-dried product and, therefore, the reconstitution of the liposome dispersion. In the current Rapid Fire the feasibility of freeze-drying hydro-alcoholic liposomal dispersions is discussed, focusing the attention on residual ethanol content and possible protectant. In particular, the effect of threalose, poly(vinyl pyrrolidone) K12 and a combination thereof on the quality attributes of lyophilized products will be presented.