Controlled release of biomolecules from pH-sensitive hydrogels prepared by radiation polymerization

Copolymers of 2-hydroxyethyl methacrylate and methacrylic acid based hydrogels were studied as hydrogel drug delivery systems. Radiation copolymerization of 2-hydroxyethyl methacrylate and methacrylic acid (mixed with 3,3'-azobis(6-hydroxy benzoic acid)(ABHB) as an azo derivative of 5-aminosalicylic acid were carried out with various amounts of methacryloyloxyethyl esters of terephthalic acid for crosslinking. The polymer structures were characterized by FTIR, H-1 NMR, C-13 NMR spectroscopy and glass transition temperature (Tg). The hydrolysis of the drug-polymer conjugates were carried out in dialysis bags containing aqueous buffer solutions (pH 1 and 7.4) at 37degreesC. The drug-release profiles indicate that the amount of drug release depended on the degree of swelling and crosslinking.