Preparation and characterization of a pH-responsive poly(HEMA-IA) hydrogel for oral quercetin delivery

Hydrogels sensitive to pH changes were prepared with the aim of transporting quercetin (QC) to the intestine, in order to improve its bioavailability and take advantage of its bioactive potential. The hydrogels were obtained from 2-hydroxyethyl methacrylate (HEMA), itaconic acid (IA), and ethylene glycol dimethacrylate (EGDMA) as crosslinker via free radical polymerization. The prepared hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance spectroscopy (SSNMR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), and their swelling behavior at different pH values was also evaluated. The QC was incorporated into the hydrogels by adsorption, showing a dependence on IA content but mainly on the amount of crosslinker. The release studies were carried out in media simulating gastric fluid (pH 2.2) and intestinal fluid (pH 7.4). The results showed a sustained and pH-dependent release profile, with higher release under intestinal conditions. The release kinetics were fitted to the Korsmeyer–Peppas model, indicating an anomalous (non-Fickian) transport mechanism. These results indicate that the developed hydrogels are suitable for transporting QC to the intestine, favoring its release in this medium.