Direct Retrieval of Biomechanical and Hydrodynamic Parameters for Drug Carrier Liposomes Using Conventional Extrusion Processes.

Physical parameters such as membrane elasticity and solution viscosity in a liquid medium play crucial roles in the effectiveness of drug delivery. Liposome formulations, used in both research and clinical contexts, are usually designed to achieve desired chemical stability, particle size, and drug encapsulation efficiency. However, meeting such requirements may not suffice in order to succeed in in vivo tests, which can be frustrated due to poor evaluation of biomechanical conditions. In this work, we introduce simple biomechanical evaluation protocols that make use of conventional pressure-based liposome extrusion as well as dynamic light scattering results to extract elastic (mechanical) and hydrodynamic (viscosity) properties of colloidal solutions of liposomes. We describe a sequence of analytical steps that need to be carried out in order to obtain macroscopic results that are directly comparable to those of other methods. Two distinct and complementary procedures are presented: the first uses a systematic variation of extrusion pressure, giving access to the viscosity of the solution, and the second being a statistical evaluation of the particle size distribution obtained by dynamic light scattering, providing elasticity constants for liposomal systems. Both methods carry the advantage of generating results for the liposome suspension that will be applied to real systems, thereby offering a more realistic and integrative characterization compared with microscopic techniques that usually present incomplete statistical coverage.