Nepafenac-loaded cyclodextrin/polymer nanoaggregates: A new approach to eye drop formulation

Abstract

The topical administration route is commonly used for targeting therapeutics to the eye; however, improving the bioavailability of drugs applied directly to the eye remains a challenge. Different strategies have been studied to address this challenge. One of them is the use of aggregates that are formed easily by self-assembly of cyclodextrin (CD)/drug complexes in aqueous solution. The aim of this study was to design a new eye drop formulation based on aggregates formed between CD/drug complexes. For this purpose, the physicochemical properties of the aggregates associated with six CDs and selected water-soluble polymers were analysed. Complex formation was studied using differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and 1 H nuclear magnetic resonance spectroscopy ( 1 H-NMR). Results showed that HPβCD performed best in terms of solubilization, while γ CD performed best in terms of enhancing nanoaggregate formation. Formation of inclusion complexes was confirmed by DSC, FT-IR and 1 H-NMR studies. A mixture of 15% (w/v) γ CD and 8% (w/v) HPβCD was selected for formulation studies. It was concluded that formulations with aggregate sizes less than 1 μm and viscosity around 10-19 centipoises can be easily prepared using a mixture of CDs. Formulations containing polymeric drug/CD nanoaggregates represent an interesting strategy for enhanced topical delivery of nepafenac.