Design and Characterization of an Ocular Topical Liposomal Preparation to Replenish the Lipids of the Tear Film

PURPOSE. Dry eye (DE) includes a group of diseases related to tear film disorders. Current trends for DE therapy focus on providing lipid components to replace the damaged lipid layer. Formulations that contain aqueous and mucin-like compounds may have additional therapeutic benefits for DE patients. The aim of this work was to design and evaluate novel formulations having the potential to become topical treatment for DE. METHODS. Unpreserved liposomal formulations composed of phosphatidylcholine (PC), cholesterol, and alpha-tocopherol (vit E) were prepared by the thin-film hydration technique. Formulations were characterized in terms of liposome size, pH, surface tension, osmolarity, and viscosity. In vitro tolerance assays were performed on macrophage, human corneal, and conjunctival cell lines at short-and long-term exposures. In vivo ocular tolerance was studied after instillation of the formulation. RESULTS. The mean liposome size was less than 1 mu m and surface tension < 30 mN/m for all formulations. The final liposomal formulation (PC-cholesterol-vit E in a ratio of 8: 1: 0.8) had physiological values of pH (6.45 +/- 0.09), osmolarity (289.43 +/- 3.28 mOsm), and viscosity (1.82 +/- 0.02 mPa.s). Cell viability was greater than 80% in the corneal and conjunctival cells. This formulation was well tolerated by experimental animals. CONCLUSIONS. The unpreserved liposomal formulation has suitable properties to be administered by a topical ophthalmic route. The liposome-based artificial tear had good in vitro and in vivo tolerance responses. This formulation, composed of a combination of liposomes and bioadhesive polymers, may be used successfully as a tear film substitute in DE therapy.