Uptake and release of Dexamethasone using pH-responsive poly (2-hydroxyethyl methacrylate-co-2-(diisopropylamino) ethyl methacrylate) hydrogels for potential use in ocular drug delivery

Abstract

pH-responsive hydrogels prepared by copolymerization between 2-hydroxyethyl methacrylate (HEMA) and 2-(diisopropylamino)ethyl methacrylate (DPA) appear to be a promising system for controlling Dexamethasone 21-disodium phosphate (DXP) release behaviors for ophthalmological treatments. The incorporation and subsequent release of DXP by HEMA-DPA copolymers have been evaluated in different pH mediums and in vitro conditions. Optical and morphological characteristics, as well as wettability, drug-matrix interactions and drug-release properties, were assessed. Drug incorporation was maximum at pH 6.5 and at an initial drug concentration of 200 mg/L. Additionally, increasing the DPA content and cross-linker ratio increased the amount of loaded DXP. The amount of DXP released was approximately 70%, and the entire release process took 20–40 h. Moreover, the copolymers showed changes in the release rate in response to small pH variations (between 7.0 and 7.8). Additionally, DXP release by the copolymers far exceeded the estimated concentration of the drug absorbed in the eyes by drop administration.