Almond oil O/W nanoemulsions: Potential application for ocular delivery

In recent years, nanotechnology has allowed to formulate different ophthalmic vehicles to extend residence time in the eye after topical application, decreasing the number of instillations and improving patient's compliance. The goal of this study was to develop an oil-in-water (O/W) nanoemulsions (NEs), composed of almond oil as the inner oil phase and Hepes or Palitzsch buffer as the outer aqueous phase, stabilized by non-ionic surfactants (Tween 20 or Tween 80). By modifying the oil/surfactant/water ratio, the best nanoemulsion formulations in terms of chemical-physical characteristics for ocular application were selected. In particular, hydrodynamic diameter, size distribution, ζ-potential, microviscosity and polarity of the internal oil phase, along with pH, osmolarity, turbidity, stability in simulated eye tears and rheological properties were evaluated. Furthermore, mucoadhesive properties of selected samples have been measured by turbidimetric assay and mucin particle method to establish their potential interaction with mucin in simulated tear fluid. Finally, cytotoxicity studies using the Alamar Blue reduction assay in Y-79 (Human retinoblastoma cell line) cells have been performed, anticipating their compatibility and suitability for ocular administration.