New biodegradable hydrogels based on an acryloylated polyaspartamide cross-linked by gamma irradiation

Alpha, beta-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA), a synthetic biocompatible macromolecule, was functionalized with glycidyl methacrylate (GMA) in order to introduce in its side chains residues having double bonds and ester groups. The copolymer (PHG), obtained from PHEA and GMA, had a degree of derivatization of 29 mol%. PHG aqueous solutions are cross-linked by gamma radiation at 0 degrees C either in the presence or absence of N,N'-methylenebisacrylamide (BIS) giving rise to new hydrogel systems. In both cases gelation occurs at quite low doses (0.26 and 0.4 kGy, respectively). The obtained networks were characterized by FT-IR spectrophotometry which confirmed that the cross-linking process involves the vinyl groups of the polymer chains. Swelling measurements evidenced the high affinity of aqueous media at different pH-values towards PHG hydrogels. The sol fractions of the irradiated samples, properly purified, were characterized by FT-IR and 1H-NMR analyses and reduced viscosity measurements. Finally, in vitro chemical or enzymatic hydrolysis studies suggested that the prepared samples undergo a partial degradation at pH 1 and 10 or after incubation with enzymes such as esterase, pepsin, and alpha-chymotrypsin.