2.8. Ex Vivo Skin Penetration Studies

Ex vivo curcumin penetration from the different DLs-in-chitosan hydrogels was evaluated using the full thickness human skin in Franz diffusion cells (diffusion area of 1.77 cm², PermeGear, Bethlehem, PA, USA) [26]. The human skin originated from the excised skin panni obtained from female patients who underwent abdominoplasty, after they gave written consent (see Section 2.6). The experiments were conducted in agreement with the Declaration of Helsinki principles. The human skin for the ex vivo penetration studies was prepared as described in Section 2.6. The slices of human skin used in the skin penetration studies had a thickness of 1.10 to 1.30 mm. All DLs-in-chitosan hydrogel formulations (1.2 mL) were added in the donor chamber, whereas the receptor chamber was filled with 12.0 mL of Albunorm (5%, v/v) solution in PBS. As a control, curcumin in PG-in-hydrogel served as a control. The experiments were conducted for 8 h and sampling of the receptor medium (500 µL) was performed every hour. To maintain the sink conditions, the withdrawn receptor medium was replaced by an equal volume of fresh Albunorm^® (5%, v/v) solution in PBS. The penetrated curcumin was quantified as described in Section 2.2 using a standard curve of curcumin in Albunorm^®/PBS (1:1, v/v). Experiments were performed in three replicates.