Abstract
Purpose::
The stabilisation of the preocular tear film can be carried out with polymeric agents or through the administration of pharmaceutical nanosystems (liposomes). Treatments directed to replace a disturbed lipid layer result of therapeutic benefits for dry eye patients. This work focuses on the development of a new formulation which constituents are similar to the ones present in the tear film.
Methods::
Phospholipon 90G containing more than 95% of phosphatidilcholine (PC) purified from soy lecithin was purchased from Phospholipid GmbH (Cologne, Germany). Cholesterol, vitamine E (a-tocopherol) and trehalose were purchased from Sigma Chemical Co. (St. Louis, Missouri). Hyaluronic acid Ophthalmic grade (Mw 400.000-800.000Da) from Abaran Materias Primas (Madrid, Spain). Liposomes were prepared from PC, cholesterol and vitamin E (8:1:0.08). After extrusion they were dispersed in a hypotonic solution (equivalent to ClNa 0.6%) of hyaluronic acid. The final concentration of liposomes in the vehicle was 20mg/ml. Tonicity of formulation was adjusted with trehalose. The study of the mean particle size and distribution of liposomes was performed by photon correlation spectroscopy. Tolerance of the formulations was evaluated in human corneal-limbal epithelial cells. Cytotoxicity studies were assessed by the mitochondrial-dependent reduction of the tetrazolium salt 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide to formazan. Studies were carried out at short (15minutes) and long term (2 and 4 hours) exposures.
Results::
The size of liposomes was always lower than 1 micron. The vesicles suspended in the hypotonic solution of hyaluronic acid rendered an osmolarity value of 205 mOsm/L. Cell viability of the formulation resulted higher than 80 % in all cases (short and long exposures).
Conclusions::
The new formulation based on liposomes and hyaluronic acid presents adequate properties to be employed as a tear film substitute. Active substances can be added to liposomes in order to improve their properties.
Keywords: cornea: tears/tear film/dry eye • drug toxicity/drug effects • cornea: epithelium