3.2. Characterization of Liposomes

The average hydrodynamic diameter and polydispersity index (PDI) of the liposome dispersions were determined by dynamic light scattering using a Malvern Zetasizer Nano (Malvern Instruments Ltd., Worcestershire, UK) at 25 °C using an argon-ion laser (488 nm) operating at 10.4 mW using non-invasive backscatter optics (NIBS). A total of 20 mL of the sample was diluted into 3 mL of PBS pH 7.4 in a cuvette to make the liposomes sufficiently dilute for analysis. For data analysis, the viscosity and refractive index of water were used. The system was calibrated with a polystyrene dispersion containing particles of 100 nm. The PDI is a measure of variation in particle size within a liposome population and varies from 0 (complete monodispersity) to 1 (large variations in particle size) and was calculated according to the method of Zhao et al. [23].