Development and evaluation of nanostructured systems for cutaneous delivery of H2S-releasing corticosteroids for skin inflammatory diseases.

Psoriasis is an immune-mediated chronic inflammatory disease that causes major psychosocial impact. Topical corticosteroids represent the standard pharmacological treatment for mild-to-moderate disease, but their local and systemic adverse effects reinforce the need for treatment innovations. Here we developed lamellar phase-based formulations for topical delivery of a hybrid dexamethasone and hydrogen sulfide (H2S) donor molecule (Dexa-TBZ), aiming to potentiate the effects of the glucocorticoid with H2S. They offer the possibility to obtain precursor formulations free of water that originate lamellar phases upon water addition, preventing drug hydrolysis during storage. Two groups of formulations were developed varying the surfactants and oil phase types and content. Systems containing 20 and 70 % of water formed, respectively, bulk lamellar phase and a more fluid formulation consisting of dispersed droplets (< 1000 nm) stabilized by lamellar phase. Both presented pseudoplastic behavior. Dexa-TBZ was incorporated at 1 %, remaining stable for 8 h. Drug content decreased to ∼80 % after 1 week in precursor formulations free of water, but remained stable after that. Without causing changes to the cutaneous barrier function ex vivo or to the histological structure of the skin in vivo, the formulation containing phosphatidylcholine as surfactant and 70 % of water promoted 1.8- and 2.7-fold increases in Dexa-TBZ penetration in the stratum corneum and epidermis+dermis, respectively, compared to a control solution, demonstrating their potential applicability as topical delivery systems.