Tacrolimus phospholipid based nanomicelles as a potential local delivery system for corneal neovascularization therapy

Introduction: Tacrolimus, an immunosuppressive agent, has been shown to be an effective treatment against corneal neovascularization (CNV). However, the poor solubility of this compound restricts its clinical application. The goal of this study was to incorporate tacrolimus into phospholipid-bile salt mixed micelles. Methods and Results: Tacrolimus loaded phospholipid-bile salt mixed micelles were prepared, employing three different methods of direct dispersion, thin film hydration, and remote film loading, and the effects of various formulation parameters (type of dispersion medium, phospholipid to bile salt molar ratio, lipid-to-drug (L/D) molar ratio, time of probe sonication, and type of bile salt) on the physicochemical characteristics of the mixed micelles were assessed. Remote film loading method indicated higher efficacy for drug entrapment in comparison to the other methods. Encapsulation of tacrolimus within the micelles increased remarkably by the use of sodium taurocholate (NaTC) as bile salt, higher phospholipid percentage, and increasing the total lipid level. Atomic force microscopy (AFM) studies confirmed the size and size distribution of the mixed micelles and their spherical morphology. It was observed that release of tacrolimus from the micelles was in a controlled manner, without an initial burst. Conclusions: By adjusting process and formulation factors, phospholipid-bile salt mixed micelles with high entrapment efficiency of (99.5 %) and controlled release behavior were achieved, which possess great potential to be valuable carriers for ocular delivery of tacrolimus for the treatment of CNV. Keywords: Mixed micelles, Phosphatidylcholine, Bile salt, Tacrolimus, Corneal neovascularization