Ammonium bicarbonate as porogen to make tetracycline-loaded porous bioresorbable membranes for dental guided tissue regeneration: failure due to tetracycline instability

The goal of this work was to manufacture a bioresorbable porous membrane aimed at both promoting osseous regeneration in oral surgery and delivering an antibiotic drug locally. The selected design consisted of a porous poly(D,L-lactic acid) matrix having a closed smooth face on one side to prevent inner migration of conjunctive and epithelial cells, and the rest of the membrane presenting open porosity to allow in-growth of osseous neotissue. The antibiotic drug was tetracycline because of its large antibacterial spectrum and its osteogenetic activity. Solvent casting/particulate leaching and gas foaming/salt leaching methods were selected to create the porosity, and ammonium bicarbonate was selected as thermosensitive water-soluble porogen because other studies reported that sodium chloride was difficult to remove totally. One-side-skinned, porous permeable membranes were successfully obtained. However, deleterious alterations of the drug were observed that were assigned to the basicity of the porogen, thus precluding any practical use in vivo.