Formulation and characterization of transfersomes for ocular delivery of tonabersat.

Transfersomes (TFS) are deformable vesicles, known for their ability to enhance transdermal drug penetration. This study aimed to evaluate whether TFS can also enhance ocular delivery of poorly soluble tonabersat. TFS were prepared using Phospholipon^® 90G with Tween^® 80 as the edge activator. The effect of formulation parameters (edge activator and cryoprotectant concentrations) on TFS characteristics were evaluated using a full factorial design. The optimized TFS eyedrop was characterized for particle size, zeta potential, deformability, entrapment efficiency (EE), drug content, pH, osmolality and TFS stability over 3 months at different storage conditions. Furthermore, drug penetration into the cornea, conjunctiva, eyelid, and sclera-choroid after topical application was studied ex vivo using a tonabersat solution in medium chain triglycerides as the control. The optimized TFS formed spherical unilamellar vesicles with a mean diameter <130 nm, EE >80%, and were stable at -20 and 5 ± 3 °C for up to 3 months. The TFS eyedrop resulted in significantly greater ocular penetration than the control without affecting the barrier properties of the tested tissues. Drug penetration into different ocular tissues was compared, shedding light on the penetration mechanism of TFS. Overall, this study demonstrates that TFS provide a promising alternative for the ocular delivery of tonabersat.