Engineering Ophthalmic Nanoemulsion Platforms: Design Principles and Translational Applications in Ocular Drug...

Due to physiological constraints that negatively affect the efficiency of conventional ocular preparations, such as fast tear turnover, poor corneal penetration, as well as short in-precornereal resident times, ocular drug delivery has long been a technical challenge. Nanoemulsion strategies based on engineering principles have been identified as a promising solution to overcome these challenges for improved solubilization, ocular bioavailability, as well as drug preparation stability. An eye preparation nanoemulsion consists of water, an oil phase, surfactants, as well as a cosurfactant, forming a kinetically stable colloidal system characterized by a mean particle diameter measuring less than 200 nm. The design principles and translation properties of ocular nanoemulsion systems are discussed in this review. Formulation components and the manufacturing methods, along with the stability problems and recent advances, are discussed. The suitability of the systems to both high-energy production methods (such as spontaneous emulsification, ultrasonication, and high-pressure homogenization) and the stability of the ocular nanoemulsions and recent advances on novel methods such as stimuli-sensitive, mucoadhesive, or positive nanoemulsions will be discussed. Despite these advantages, however, some challenges such as stability for a extended period, complexity, and cost of production still exist. In conclusion, customized ocular nanoemulsion delivery systems are quite viable and flexible research strategies for successful ocular drug delivery.