2.2.3. Characterization of the Liposomes

The average particle size, zeta potential, and polydispersity index (PDI) of the liposomes were evaluated with the dynamic light scattering technique using a Zeta-sizer Nano ZS (Malvern, Worcestershire, UK). The microstructure of the liposomes was observed using an optical microscope (4XC-W, Jinanchenda, Jinan, China).

The encapsulation efficiency (EE) was measured according to the literature with some modifications [15]. Solutions of various concentrations (0.5, 1.0, 1., 2.0, and 2.5 μL/mL) of the anthocyanin were dissolved in a buffer solution (pH 6.86), and the absorbance was measured at 620 nm. The standard curve of the anthocyanin was analyzed as the equation Y = 0.221x + 0.010 (R<sup>2</sup> = 0.9981). Then, a certain amount of BALs was immersed in a buffer solution and centrifuged at 8000 rpm for 20 min. Free anthocyanins were isolated from the supernatant, and their absorbance was measured at 620 nm. Then, the concentration of free anthocyanins was calculated with the standard curve. Finally, the EE of the anthocyanin was obtained as follows:

$$\text{EE}(\%) = \frac{\text{Total antibocycles} - \text{Free antibocycles}}{\text{Total anthropians}} \tag{1}$$
