Perspective use of bio-adhesive liquid crystals as ophthalmic drug delivery systems.

The success of many drugs in ophthalmic treatments is hindered by their physico-chemical properties and the limited precorneal retention time. Here, lyotropic liquid crystals are proposed as a new ophthalmic drug delivery system. Acyclovir was chosen as model drug for its solubility and its controlled release from cubic phase was achieved. We demonstrated the effortless application of lamellar phase on corneal surface and its ability to convert itself in cubic phase in situ. While the complex viscosity of lamellar phase was affected by temperature (5.1 ± 1.4 kPa·s at 25 °C and 0.12 ± 0.001 Pa·s at 35 °C, respectively), the cubic phase shown no changes in viscosity values and shear thinning behaviour at both temperatures and even in presence of the drug The degradation kinetic of drug-loaded cubic phase was slightly slower than the empty formulation, recording 27.92 ± 1.43% and 33.30 ± 3.11% of weight loss after 8 h. Ex vivo studies conducted on porcine eyeballs and isolated cornea confirmed the instantaneous transition to cubic phase, its ability to resist to gravity force, and forced dripping of simulated tear fluid. Histopathological investigation showed how treated cornea did not report changes in epithelial and stroma structures. In summary, lyotropic liquid crystals could represent an advantageous ophthalmic drug delivery system.