Controlled release of biomolecules from pH-sensitive network polymers prepared by radiation polymerization.

Copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) based hydrogels containing 5 and 10% of a cross-linking agent were studied as drug delivery systems. Terephthalic acid was covalently linked with HEMA, abbreviated as CA. Radiation copolymerization of HEMA and MAA, mixed with a particulate glibenclamide with the various ratios CA as crosslinking agent were carried out at the room temperature. The structure of the CA was confirmed by FTIR, H NMR and C NMR spectroscopy. The compositions of the cross-linked three-dimensional polymers were determined by FTIR spectroscopy. Glass transition temperature (T) of the network polymers was determined calorimetrically. The hydrolysis of drug-polymer conjugates was carried out in cellophane membrane dialysis bags containing an aqueous buffer solution (pH 7.4 and pH 1) at 37 degree C. The drug-release profiles indicate that amount drug release depends on their degree of swelling and cross-linking.