Freeze-dried bioadhesive vaginal bigels for controlled release of Tenofovir

Nowadays, million women live with the human immunodeficiency virus (HIV) worldwide and many of them are dying per year, particularly in Sub-Saharan Africa. The development of systems that can be accessed by this population group to prevent the sexual transmission of the virus is therefore necessary. The aim of this work was the formulation of freeze-dried bioadhesive vaginal bigels releasing Tenofovir in a controlled manner. Systems containing three different proportions of guar gum hydrogel and sesame oil were prepared, adding Span®60 or Span®60 and Tween®60 as surfactants. Drug and excipients were evaluated by cytotoxicity assays, showing no toxicity at the concentrations tested neither for the drug nor any of the excipients. Fresh formulations were characterised through texture analyses and confocal laser microcopy. The system with the lowest guar gum hydrogel/sesame oil proportion and containing Span®60 and Tween®60 (batch ST1) had the highest consistency and adhesion capacity according to texture analyses. Furthermore, a genuine bigel microstructure was observed. After freeze-drying, swelling, bioadhesion and drug release tests were performed on the resulting systems. ST1 showed the longest bioadhesion time and the most controlled release, as well as a low swelling grade, becoming an interesting option for preventing HIV sexual transmission in women.