Preparation, characterization and preliminary in vivo safety evaluation of cationic nano-emulsions containing α-lipoic acid after ocular administration in NZW rabbits

Oxidative stress has a considerable role in prevalence probability of many widely common eye problems including cataract, diabetic retinopathy and age-related macular degeneration. It has been revealed that using oral antioxidants could prevent or delay the incidence of these problems. α-Lipoic acid (ALA) is an endogenous molecule with an excellent antioxidant properties which makes its oral and topical usage suitable as supplement. The special characteristics of cationic nano-emulsions (NEs) makes them an optimum carrier for ocular drug delivery. These nanoparticles provide a high drug loading efficiency for water insoluble substances like ALA and improves the penetration through electrostatic interactions with negatively charged ocular surface. 

In this study, ALA loaded cationic NEs were prepared and characterized by size, release profile, loading efficiency and their physicochemical properties. After thermodynamic stability evaluations, the animal studies conducted to examine the safety of final preparation in rabbit. 

Results demonstrated a drug loading efficiency of 61% for ALA and the size of cationic NEs increased from 132 nm to 289 nm after ALA entrapment. The prepared nanoparticles showed acceptable physicochemical properties and released up to 10% of loaded ALA during 6 h. the final preparation passed thermodynamic stability tests and was safe in ocular irritancy studies. 

In this study the developed cationic NE formulation of ALA demonstrated to be useful for further evaluations in future.