This study was aimed to develop a novel microemulsion that contained oleth-5 as a surfactant to enhance the oral absorption of all-trans retinoic acid (ATRA). The prepared microemulsion was evaluated for its particle size, shape, zeta potential, in vitro release, in vitro intestinal absorption, intestinal membrane cytotoxicity and stability. The obtained microemulsion was spherical in shape with a particle size of <200 nm and a negative surface charge. The in vitro release of the ATRA-loaded microemulsion was best fit with the zero-order model. This microemulsion significantly improved the intestinal absorption of ATRA. Confocal laser scanning microscopy analysis using a fluorescent dye-loaded microemulsion also confirmed the intestinal absorption result. The intestinal membrane cytotoxicity of the ATRA-loaded microemulsion did not differ from an edible oil (fish oil). Stability testing showed that the ATRA-loaded microemulsion was more stable at 25°C than 40°C.

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Ultradeformable liposomes containing penetration enhancers were created to deliver NaFl. Vesicles were investigated for their particle size, zeta potential, NaFl entrapment efficiency (%EE), loading efficiency, and in vitro skin penetration. The vesicles obtained were spherical in shape, with a particle size of less than 100 nm and a negative surface charge (-6 to -11 mV). The %EE of NaFl loaded in vesicles ranged from 37 to 48%. Ultradeformable liposomes with monoterpenes (d-limonene, 1,8-cineole and geraniol) significantly improved NaFl penetration through the skin. Confocal laser scanning microscopy analysis confirmed skin-penetration results and was used to evaluate the behavior of hydrophilic compounds penetrating through the skin.

This study aimed to develop ultradeformable liposomes (ULs) with fatty acids, namely, oleic, linoleic, and linolenic acid, to improve the skin penetration of rosmarinic acid. This study also investigated the vesicle-skin interaction and skin penetration pathway of ULs with fatty acids using the co-localization technique of multifluorescently labeled particles. The prepared ULs were characterized in terms of size, surface charge, size distribution, shape, % entrapment efficiency (% EE), and % loading efficiency (% LE). The prepared ULs with fatty acids had an average particle size between 50.37 ± 0.3 and 59.82 ± 17.3 nm with a size distribution within an acceptable range and exhibited a negative surface charge. The average % EE and % LE were 9 and 24.02, respectively. The in vitro skin penetration study found that ULs with oleic acid could significantly increase the skin penetration of rosmarinic acid compared to ULs. According to confocal laser scanning microscopy observations, this study suggested that UL vesicles attach to the skin before releasing the entrapped drug to penetrate the skin. These findings suggested that ULs with oleic acid penetrated the skin via the transfollicular pathway as a major penetration pathway.