Smart vaginal bilayer films of Tenofovir based on Eudragit® L100/natural polymer for the prevention of the sexual transmission of HIV

[Display omitted] •Vaginal mucoadhesive bilayer films are obtained from Eudragit® L100/natural polymer.•Eudragit® L100 hinders the destructuring of the natural polymer layer in vaginal films.•Tragacanth gum-based bilayer films show high ex vivo mucoadhesion.•Eudragit® L100 acts in Tenofovir release: fast in seminal fluid, slow in vaginal fluid. In the absence of an effective vaccine, vaginal microbicides are essential for preventing the sexual transmission of HIV to women. Antiretroviral vaginal films have emerged as promising choices, especially those offering mucoadhesivity and controlled drug release. Tenofovir-loaded bilayer films based on Eudragit® L100 (EL100) and a biopolymer – gum arabic, karaya gum, pectin or tragacanth gum – were developed in a single-stage process. Cytotoxicity studies in three human cell lines indicated no toxicity of the excipients at the concentrations tested. Raman spectroscopy and SEM confirmed the formation of the two layers and their anchoring. Texture analysis showed no major differences between the batches. The swelling of the film is conditioned by its biopolymer nature and by the amount of EL100, which acts as structuring agent thus enhancing swelling. Tragacanth gum-based batches showed high mucoadhesion regardless the amount of EL100. The controlled release of Tenofovir in simulated vaginal fluid was faster in the presence of simulated seminal fluid due to the dissolution of EL100. Films containing 400 mg of EL100 and tragacanth gum are promising candidates for future studies, as they could sexually safeguard women from HIV for at least one week and ensure greater protection during intercourse.