Atopic dermatitis is a chronic, non-infectious inflammatory skin disease accompanied by itching and recurrent eczematous lesions. Treatment is aimed at controlling and preventing inflammation and itching of the skin, also, regular, and proper skin care is of key importance. The first choice for the local treatment of atopic dermatitis are corticosteroids incorporated into classic pharmaceutical dosage forms such as creams and ointments. Therefore, the objective of our study was to contribute to the improved treatment of atopic dermatitis by incorporating betamethasone dipropionate into modern delivery systems, namely lyotropic liquid crystals. The latter are extremely favorable for dermal application due to their specific microstructure. In addition, the choice of excipients was crucial, with flaxseed or hemp oil being chosen as the oil phase due to its high content of essential fatty acids with anti-inflammatory action being beneficial for atopic skin, while the emulsifier phase consisted of biocompatible surfactants that promote the formation of lyotropic liquid crystals, namely lecithin in combination with Tween 80 or Montanov 68. Water was chosen as the hydrophilic phase. Within the experimental work, the areas of liquid crystal were determined based on organoleptical evaluation for four different combinations of oil phase and mixtures of surfactants by (pseudo)ternary phase diagrams construction. Selected samples (with and without incorporated betamethasone diproprionate) on the dilution line (i.e., at different water proportions) with a constant ratio of surfactants and oil phase 6/4 were used for further microstructure evaluation by polarization microscopy. For samples with Tween 80, the formation of lamellar liquid crystals was confirmed along the entire dilution line, while for Montanov 68 the formation of lamellar mesophases was confirmed only for specific samples depending on the proportions of the aqueous phase. The oil phase as well as the incorporation of the active substance did not affect the formation of lamellar liquid crystals. In the framework of further rheological analysis, we found that the incorporation of the active substance is reflected in the changed values of viscosity and dynamic modules in the case of samples with Tween 80. However, there were no significant changes in the samples with Montanov 68. Evaluation of the microstructure was performed at room temperature (25 °C), skin temperature (32 °C) and body temperature (37 °C), and the microstructure was maintained even at higher temperatures as confirmed by polarization, while temperature-dependent changes in viscosity were detected in case of certain samples.
To conclude, the newly developed lyotropic liquid crystals are suitable for the incorporation of betamethasone diproprionate and represent a promising drug delivery system for the treatment of atopic dermatitis.
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