The role of aggregation and ionization in the chemical instability of Amphotericin B in aqueous methanol.

Amphotericin B (AmB) is a potent antimicrobial agent used in clinical practice. Nevertheless, the mechanism of its aqueous instability remains not yet fully understood, especially the role that its aggregation state plays in this process. Therefore, the current study used an aqueous methanol media to evaluate the AmB instability as a function of pH-, organic solvent- and concentration-dependent ionization and aggregation. To reach this goal, the aggregation status and instability were determined using UV-vis spectroscopy, LC-MS and HPLC. Moreover, not only the hydrolytic degradation products were identified by UV-vis spectroscopy and LC-MS, but also, the degradation rate constants were estimated by nonlinear regression. The results indicated that monomeric AmB was the predominant species under pH conditions, wherein the substrate was cationic (pH < 4) or anionic (pH > 9). On the other hand, aggregated AmB form was the predominant species for the zwitterionic substrate (at methanol concentration < 30 %(v/v)). Anionic substrate degraded by specific base-catalyzed lactone hydrolysis. Oxidation accounted for the loss of zwitterionic substrate. Aggregated zwitterionic AmB exhibited lower stability than monomeric zwitterionic AmB under neutral pH conditions. These studies are a step forward in comprehending the degradation kinetics of AmB in aqueous medium. In fact, along with our previous research on AmB instability in oils, it leads to a better understanding of the AmB stability in complex systems with an oil-water interface, such as disperse lipid systems.

A Functional Wound Dressing as a Potential Treatment for Cutaneous Leishmaniasis.

Cutaneous leishmaniasis (CL) is a parasitic disease characterized by progressive skin sores. Currently, treatments for CL are limited to parenteral administration of the drug, which presents severe adverse effects and low cure rates. Therefore, this study aimed to develop poly(vinyl-alcohol) (PVA) hydrogels containing Amphotericin B (AmB) intended for topical treatment of CL. Hydrogels were evaluated in vitro for their potential to eliminate promastigote forms of Leishmania spp., to prevent secondary infections, to maintain appropriate healing conditions, and to offer suitable biocompatibility. AmB was incorporated into the system in its non-crystalline state, allowing it to swell more and faster than the system without the drug. Furthermore, the AmB release profile showed a continuous and controlled behavior following Higuchi´s kinetic model. AmB-loaded-PVA-hydrogels (PVA-AmB) also showed efficient antifungal and leishmanicidal activity, no cytotoxic potential for VERO cells, microbial impermeability and water vapor permeability compatible with the healthy skin's physiological needs. Indeed, these results revealed the potential of PVA-AmB to prevent secondary infections and to maintain a favorable environment for the healing process. Hence, these results suggest that PVA-AmB could be a suitable and efficient new therapeutic approach for the topical treatment of CL.