Skin permeation experiment

Locally fabricated horizontal Franz diffusion cells, having a surface area of 4.91 cm², were utilized to perform such an experiment for APO suspended in propylene glycol (control) as well as the optimized formulation (F2). Each sample (equivalent to 3.10 ± 0.115 mg APO) was introduced to the stratum corneum (SC), comprising the donor chamber of the excised rat skin, while the dermal side faced the receptor one that was filled with 50 mL phosphate buffer (PB (pH 7.4)) and shaken at 100 rpm in a shaking incubator (GFL Gesellschaft für Labortechnik, Burgwedel, Germany) maintained at 37 ± 0.5 °C. Such assessment was carried out in triplicate.

At preplanned time intervals (0.5, 1, 2, 3, 4, 6, 8, and 24 h) and to keep up a steady volume during the experiment, aliquots of 3 mL were collected from the receptor compartment and resubstituted with the same volume of PB (pH 7.4). The huddled aliquots were filtered by 0.45 µm membrane filters (EMD Milli-pore, Billerica, MA, USA) and quantified spectrophotometrically for permeated drug amounts using UV–Vis spectrophotometer at 278 nm. To eliminate whichever interference deriving either from rat skin or formula constituents, the same protocol was fulfilled utilizing plain CPT/CS hybrid NPs, as blank, corresponding to the investigated medicated formula (F2).