Evaluation of transdermal delivery of nanoemulsions inex vivoporcine skin using two-photon microscopy and confocal laser-scanning microscopy

Abstract

This study experimentally evaluates the self-targeting ability of asiaticoside-loaded nanoemulsions compared with nontargeted nanoemulsions in ex vivo experiments with porcine skin samples. Homebuilt two-photon and confocal laser-scanning microscopes were employed to noninvasively examine the transdermal delivery of two distinct nanoemulsions. Prior to the application of nanoemulsions, we noninvasively observed the morphology of porcine skin using two-photon microscopy. We have successfully visualized the distributions of the targeted and nontargeted nanoemulsions absorbed into the porcine skin samples. Asiaticoside-loaded nanoemulsions showed an improved ex vivo transdermal delivery through the stratum corneum compared with nonloaded nanoemulsions. As a secondary measure, nanoemulsions-applied samples were sliced in the depth direction with a surgical knife in order to obtain the complete depth-direction distribution profile of Nile red fluorescence. XZ images demonstrated that asiaticoside-loaded nanoemulsion penetrated deeper into the skin compared with nontargeted nanoemulsions. The basal layer boundary is clearly visible in the case of the asiaticoside-loaded skin sample. These results reaffirm the feasibility of using self-targeting ligands to improve permeation through the skin barrier for cosmetics and topical drug applications.

Size-dependent penetration of nanoemulsions into epidermis and hair follicles: implications for transdermal delivery and immunization

“…It should be noted that nanoemulsions are different to microemulsions, because the latter are referred to thermodynamically stable isotropic liquids formed by mixing oil, water, and surfactants together [28]. Due to the fluidic microstructure, high solubilizing capacity for lipophilic drugs and excellent skin affinity, nanoemulsions show superior transdermal efficiency to rigid nanoparticles [3, 29]. In addition, the compositions of nanoemulsions, i.e.…”

“…Due to similarity in compositions, it is basically impossible to discriminate nanoemulsions from dermal lipids. Although fluorescence labelling provides important information on the dermal penetration of nanoemulsions [29, 34–36, 41], the images merely demonstrate the distribution of the label which may diffuse out of the nanoemulsions while moving through the skin [33]. Furthermore, dermatopharmacokinetic analysis of the nanoemulsion components across the skin depth was adopted to answer the question [33].…”