Development, Optimization, and In Vitro/In Vivo Evaluation of Azelaic Acid Transethosomal Gel for Antidermatophyte Activity

Abstract

Treatment of dermatophytosis is quite challenging. This work aims to investigate the antidermatophyte action of Azelaic acid (AzA) and evaluate its efficacy upon entrapment into transethosomes (TEs) and incorporation into a gel to enhance its application. Optimization of formulation variables of TEs was carried out after preparation using the thin film hydration technique. The antidermatophyte activity of AzA-TEs was first evaluated in vitro. In addition, two guinea pig infection models with Trichophyton (T.) mentagrophytes and Microsporum (M.) canis were established for the in vivo assessment. The optimized formula showed a mean particle size of 219.8 ± 4.7 nm and a zeta potential of -36.5 ± 0.73 mV, while the entrapment efficiency value was 81.9 ± 1.4%. Moreover, the ex vivo permeation study showed enhanced skin penetration for the AzA-TEs (3056 µg/cm²) compared to the free AzA (590 µg/cm²) after 48 h. AzA-TEs induced a greater inhibition in vitro on the tested dermatophyte species than free AzA (MIC₉₀ was 0.01% vs. 0.32% for T. rubrum and 0.032% for T. mentagrophytes and M. canis vs. 0.56%). The mycological cure rate was improved in all treated groups, specially for our optimized AzA-TEs formula in the T. mentagrophytes model, in which it reached 83% in this treated group, while it was 66.76% in the itraconazole and free AzA treated groups. Significant (p < 0.05) lower scores of erythema, scales, and alopecia were observed in the treated groups in comparison with the untreated control and plain groups. In essence, the TEs could be a promising carrier for AzA delivery into deeper skin layers with enhanced antidermatophyte activity.

Keywords: Microsporum canis; Trichophyton mentagrophytes; antidermatophyte; azelaic acid; guinea pig model; thin film hydration; transethosomes.

Figure 1

3D-response surface plots showing the effect of the independent variables on PS (A,B), ZP (C,D), and EE% (E,F). (A,C,E) where the used SAA is Labrafil, (B,D,F) where the used SAA is SDC.

Figure 2

Characterization of the optimized formula; (A) Transmission electron microscopy of the optimized AzA-TEs; (B) FTIR spectra of the free AzA, plain formula, and optimized AzA-TEs.

Figure 3

In vitro and ex vivo characterizations of the optimized formula; (A) In vitro drug release of the free AzA and the optimized AzA-TEs; (B) Ex vivo fluxes of the free AzA and the optimized AzA-TEs.

Figure 4

Means of erythema (A), scales (B), and alopecia (C) scores in Microsporum canis and Trichophyton mentagrophytes infected guinea pigs in different groups. * p < 0.05 (plain gel); † p < 0.05 (AZA gel); ^® p < 0.05 (itraconazole); ¶ p < 0.05 (AzA-TEs gel) versus untreated positive controls. p-value was estimated using exact Wilcoxon test.

Figure 5

M. canis (A) and T. mentagrophytes (B) infected guinea pig models at day 14 post-treatment. G1: infected untreated control group; G2: infected and treated with 10 mg/kg itraconazole once daily through oral gavage; G3: AzA-TEs gel-treated group (5 mg/kg); G4: AzA gel, and G5: plain-gel-treated groups topically twice a day.