Novel mixed vesicles containing lactobacilli biosurfactants for vaginal delivery of econazole nitrate

Vulvovaginal candidiasis (VVC) is one of the most common cause of vaginitis affecting 70-75% of women at least once during their lives. The treatment of VVC involves the use of topical and oral azoles, such as econazole nitrate (EN), a broad-spectrum antifungal and lipophilic drug. The bioavailability and antifungal effects of econazole are limited by its poor water solubility [1]. In this regard, its incorporation in vesicular systems may improve its availability at the application site, thus reducing the necessary daily-dose and consequently increasing patient compliance. Phospholipid vesicles can be enriched with surfactant molecules in order to modify their functional properties and allow an efficient drug delivery. Traditionally, surfactants are produced by organic chemical reactions from petroleum feedstocks. Compared with synthetic surfactants, biosurfactants (BS) are “green products” that show several advantages such as lower toxicity and higher biodegradability [2]. BS are amphiphilic biological compounds produced extracellularly or as part of the cell membranes by a variety of microorganisms, including probiotic lactobacilli, and exhibit pronounced surface and emulsifying activities [3]. The first step of this work was to characterize BS produced by Lactobacillus gasseri BC9, isolated from the vagina of a healthy premenopausal woman, in terms of chemical structure and technological parameters. Secondly, the lipid film hydration method was employed for the formulation of EN- loaded and unloaded mixed vesicles (MV), containing BS (BS-MV) or Tween 80 (tween-MV). Vesicles were characterized in terms of morphology, size and zeta-potential. Stability, encapsulation efficiency, mucoadhesion properties and release of EN from mixed vesicles were also evaluated by in vitro studies. Moreover, the ability of MV to exert antimicrobial activity against C. albicans, the most frequent etiologic agent of VVC, was evaluated. BS produced by L. gasseri BC9 was composed by peptide-like molecules containing hydrocarbon chains, as shown by FT-IR spectrum, and possessed a high surface activity together with a low critical micelle concentration. Mixed vesicles presented a spherical shape (as confirmed by AFM images) and a diameter in the range of 226-337 nm (as confirmed by DLS measurements). Compared to tween-MV, loaded vesicles containing BS showed higher size and a lower zeta-potential value, probably due to the interaction between the drug and BS. This interaction also allowed the entrapment of a great amount of EN and sustained its release over the time. Furthermore, BS-MV showed good stability over the time and interesting mucoadhesive properties. Finally, the antimicrobial tests demonstrated the inhibitory activity against C. albicans of EN formulated in the MV. Additional investigations on mixed vesicles and their incorporation in a suitable gel vehicle should be considered to further evaluate their applicability in vaginal drug delivery. [1] Firooz A, Nafisi S, Maibach HI. Novel drug delivery strategies for improving econazole antifungal action. Int J Pharm. 2015; 495(1):599-607. [2] Vaz DA Gudiña, EJ, Alameda EJ, Teixeira JA, Rodrigues LR. Performance of a biosurfactant produced by a Bacillus subtilis strain isolated from crude oil samples as compared to commercial chemical surfactants. Colloids Surf B Biointerfaces. 2012; 89:167-74. [3] Van Hamme JD, Singh A, Ward OP. Physiological aspects. Part 1 in a series of papers devoted to surfactants in microbiology and biotechnology. Biotechnol. Adv. 2006; 24:604-620.