Tocotrienol-Rich Fraction Nanoemulsion: A Novel Approach for Ocular Drug Administration

Tocotrienol-rich fraction (TRF), a substance extracted from palm oil, contains tocotrienol, which was shown to delay cataract development and progression in an experimental cataract model. Other than that, TRF also reduced retinal neurodegenerative changes in diabetic retinopathy animal models. However, TRF is an oily substance, which makes it difficult to apply topically to the eye, which is the most favorable route of administration for ocular tissue. Topical ocular drug delivery is less invasive and more targeted, thus producing fewer systemic adverse effects. Nanoemulsion is one of the promising colloidal drug delivery systems for topical ocular use. In this study, we aimed to investigate the optimum ratio of surfactant, oil, and water needed to develop a TRF nanoemulsion formulation that was suitable for ocular use. The solubility of TRF in different types of surfactants was also investigated. Ternary phase diagrams (TPDs) were constructed using three different surfactant systems (Poloxamer 188, Tween 80, and a combination of Tween 80 and Span 80). The result showed 1 % w/w TRF was soluble in Tween 80 and a combination of Tween 80 and Span 80 solution, but not in Poloxamer 188. Observations on isotropic, turbid, or multilayer formulations were plotted on TPD. Among the TPD constructions, the TPD consisting of Miglyol 812 with TRF (oil phase)/Tween 80/ Water system (aqueous phase) was selected due to the large isotropic region. Five formulations (TRF 1, TRF 2, TRF 3, TRF 4, and TRF 5) were chosen based on the TPD selected, and the formulations were prepared by the low-energy emulsification method. The physicochemical characterization of their size, polydispersity index (PDI), zeta potential, and pH of these formulations was evaluated. Among the formulations prepared, TRF 5 was the most stable formulation with droplet size, PDI, zeta potential, and pH values of 11.44 nm, 0.062, -7.75 mV, and 6.57, respectively. Further studies are needed to determine the ocular toxicity, penetration, and pharmacokinetics of this formulation.