*3.2. Preparation of Rivastigmine-Loaded NLC Formulations*

Rivastigmine-loaded NLC formulations (Table 1) were prepared by HPH and ultrasound technique, which were previously employed by Silva et al. [18,53]. Briefly, the lipid phase was heated above the solid lipid melting point and added to the aqueous phase, which was previously heated at the same temperature. Afterwards, the mixture was emulsified under high-speed stirring with an Ultra-Turrax® T25 (Janke and Kunkel GmbH, Staufen im Breisgau, Germany) at 13,400 rpm for 5 min. The oil-in-water (O/W) formed emulsion was sonicated by means of an VCX130 ultrasonic processor (Sonics, Wolfwil, Switzerland). The power output, with an amplitude of 75%, was applied for 15 min. The hot O/W nanoemulsion was transferred to glass vials and cooled to the room temperature (20 ± 0.5 ◦C) to form the NLC. A rivastigmine concentration of 0.12% (*w*/*w*) was added to the lipid phase before melting. Regarding the HPH, the procedure was similar, although the O/W emulsion was forced to pass through a piston gap homogenizer (Stansted High Pressure Homogenizer, Stansted Fluid Power Ltd., Harlow, UK) at 1750 bar and 80 ± 0.5 ◦C. The number of applied homogenization cycles ranged from 9 up to 18. The homogenizer was previously heated at 80 ± 0.5 ◦C with hot purified water and the temperature was kept constant to avoid lipid solidification.
