2.13. In Vitro Permeation Studies of MUP through Strat-M® Membrane and Porcine Skin

In vitro permeation studies through Strat-M membrane were carried out using Franz diffusion cells [8]. Briefly, the diffusion was carried out over an area of 2.5 cm² and a 15 mL volume of the receiver chamber. The experiment was carried out at a temperature of 37 ± 1 °C, with magnetic stirring at 100 rpm for 24 h. The receiver chamber was filled with medium composed of methanolic phosphate buffered saline in a ratio of 1:1 at pH 7.4. The nanoemulgel was placed in the donor chamber, and an aliquot (0.5 mL) was withdrawn from the receiver chamber and substituted with the same volume of fresh medium at a regular interval of 1 h for 24 h. HPLC analysis of samples was carried out without dilution.

Porcine ear skin (full thickness) was supplied by a local abattoir and was used fresh after excision or kept frozen at −18 °C for future use within one month.

In vitro skin permeation studies were carried out as outlined previously [8], using the same parameters mentioned in Section 2.13.1, except the diffusion area was 3.14 cm². The experiment was stopped after 8 and 24 h, and the formulation residues were removed from the skin before tape stripping, with and without cyanoacrylate, to determine drug within the skin [41].