Swelling properties of copolymeric hydrogels of poly(ethylene glycol) monomethacrylate and monoesters of itaconic acid for use in drug delivery

Copolymeric hydrogels of poly(ethylene glycol) monomethacrylate (PEGMA) (P) have been synthesized for use in drug‐delivery. New copolymeric hydrogels were prepared by free radical solution polymerization of PEGMA and monomethyl itaconate (MMI) or monoethyl itaconate (MEI), using ethyleneglycol dimethacrylate and tetraethyleneglycol dimethacrylate, respectively, as cross‐linkers. The effect of copolymer composition on swelling behavior, thermal decomposition and drug release was studied. Three compositions of each copolymer were studied: 70P/30MMI (or MEI), 80P/20MMI (or MEI) and 90P/10MMI (or MEI). The largest equilibrium swelling degree was observed in gels containing the highest content of MMI or MEI (84.22 ± 0.22 wt % for 70P/30MEI; 79.56 ± 0.64 wt % for 70P/30MMI). The swelling process was in accordance with Fick's Second Law. Methotrexate (MTX), an anticancer agent used in the treatment of different hyperproliferative epithelial diseases, was chosen to be loaded in the gels. The drug was included by immersion of the copolymeric disks in an aqueous solution of the drug. The amount of MTX in the xerogels was between 5.34 ± 0.06 mg MTX/g (90P/10MMI) and 14.94 ± 0.91 mg MTX/g (80P/20MEI). Two stages of thermal degradation for unloaded and MTX‐loaded gels were determined; the presence of the drug in the polymeric matrices decreased the temperature of the first stage of thermal degradation. MTX release was also in accordance with Fick's Second Law. The length of total drug release (340 ± 30 min–1502 ± 81 min) could be modulated as a function of the comonomer composition of the hydrogel. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009