Eudragit® L100/chitosan composite thin bilayer films for intravaginal pH-responsive release of Tenofovir

[Display omitted] •Eudragit® L100/chitosan blend forms bilayer films in 2-propanol after evaporation.•Higher Eudragit® L100 and plasticizer content improves the mechanical properties.•Mucoadhesion is not influenced by the amount of Eudragit® L100 or plasticizers.•The pH-responsive drug release is explained by the layer based on Eudragit® L100.•Higher Eudragit® L100 and plasticizer content allows a more controlled release. The high rate of HIV new infections and AIDS-related deaths each year make prevention tools still necessary today. Different dosage forms – including films – for vaginal administration of antiretroviral drugs have been developed for this purpose. Six batches of Tenofovir-loaded films were formulated based on Eudragit® L100 (EL100) and chitosan, containing triethyl citrate and glycerol. In all the cases films structured in two layers – the upper layer mainly attributed to EL100 and the lower layer to chitosan – were revealed by SEM. A higher content in EL100 and plasticizers improves the mechanical properties and control over drug release in the vaginal medium without affecting mucoadhesion. The EL100-based layer acts as a structuring agent that controls Tenofovir release for days in the vaginal medium while it occurs in a few hours in the presence of seminal fluid. Bilayer films with the highest tested content of EL100 and plasticizers would be the most suitable as vaginal microbicides as they are easier to administer due to their excellent mechanical properties and they offer more comfortable posology and enhanced protection against HIV during intercourse due to their pH-responsive release of Tenofovir.