Fabrication and in vitro evaluation of novel pH-sensitive poly (2-methoxyethyl methacrylate-co-itaconic acid) microgels

The present work focused on the synthesis and evaluation of cross-linked poly(2-methoxyethyl methacrylate-co-itaconic acid) [p(MEMA-co-IA)] microgels for controlled and extended drug delivery, in an attempt to improve the bioavailability of the drugs and to get maximum therapeutic benefits. A series of p(MEMA-co-IA) microgels were prepared by modified free-radical suspension polymerization using ethylene glycol dimethacrylate as cross-linker. Characterization was performed through FTIR, TGA, DSC, XRD, DLS and SEM. pH responsiveness was evaluated by equilibrium swelling studies in phosphate buffer solutions of different pH values (pH 1.2, 4, 6.5, and 7.4) with constant ionic strength. To demonstrate the potential use of microgels for drug delivery, esomeprazole magnesium trihydrate (EMT) was loaded as model drug and in vitro dissolution studies were performed. FTIR and thermal analysis confirmed the formation of cross-linked p(MEMA-co-IA) microgels. XRD indicated dispersion of drug into the network at molecular level. SEM illustrated smooth, round and uniformly distributed microspheres. A remarkably higher swelling at higher pH values (pH 6.5 and 7.4) compared to pH 1.2 demonstrated the pH-responsive nature of the microgels. All the formulations showed pH-dependent drug release following Higuchi with non-fickian mechanism of drug diffusion. In light of the results obtained from this study, it was concluded that p(MEMA-co-IA) microgels have potential to release drug in controlled manner responsive to pH of the external environment.