Synthesis and swelling behaviors of poly(2-hydroxyethyl methacrylate-co-itaconic acid) and poly(2-hydroxyethyl methacrylate-co-sodium itaconate) hydrogels as potential drug carriers

Poly(2-hydroxyethyl methacrylate-co-itaconic acid) poly(HEMA-co-IA) and poly(2-hydroxyethyl methacrylateco-sodium itaconate) poly(HEMA-co-SI) hydrogels were prepared by free-radical copolymerization method at room temperature for 24 h. N,N-methylenebisacrylamide (MBA) was used as crosslinker, and ammonium persulfate (APS) together with tetramethylethylenediamine (TEMED) was used as initiator and accelerator, respectively. To evaluate the potential of hydrogels for oral delivery of bioactive compounds, they were characterized in terms of swelling (q) in similar conditions the gastrointestinal tract (stomach pH 2.2 and intestinal pH 7.4 buffer solutions) at 37 degrees C. The hydrogels with 10 and 15 mol % IA show good pH sensitivity, and the swelling of the hydrogel with 10 mol % IA changes from q = 0.8 pH 2 to q = 3.7 pH 7. On the contrary, all hydrogels with SI have a poor response to pH, the swelling of the hydrogel with 10 mol % SI changes from q = 0.9 pH 2 to q = 1.2 pH 7. In addition, poly(HEMA-co-SI) hydrogels describe a swelling behavior known as "overshooting", which is explained through cation exchange (Na+ and H+). The structural, morphologic, and thermal characterization of the hydrogels was carried out using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA), respectively.