Swelling behavior of gamma-irradiation cross-linked elastomeric polypentapeptide-based hydrogels

Abstract

The dynamic and equilibrium swelling behavior are reported for four gamma -irradiation crosslinked elastic protein-based polymers comprised of repeating pentapeptide sequences. The elastomeric polypentapeptides, previously prepared using recombinant DNA technology, are (GVGVP)(251), (GVGIP)(260), (GVGVP GVGVP GEGVP GVGVP GVGVP GVGVP)(35)](GVGVP), and (GVGVP GVGTFP GEGFP GVGVP GVGFP GFGFP)(35)](GVGVP), where G = glycine, V = valine, P = proline, I = isoleucine, F = phenyalanine, and E = glutamic acid. These polymers had been gamma -irradiation cross-linked into elastic matrices using doses ranging from 6 to 34 Mrad. Fick's law was able to explain their initial dynamic swelling behavior. Thermal history was found to be a variable affecting dynamic swelling, The equilibrium swelling ratio was dependent on both temperature and pH (for the E-containing polymers) and analyzed using the Flory-Huggins interaction parameter. The interaction parameter could be related with the T-t mechanism developed for polypeptides. Different continuities found in the phase transitions of these polymers and poly(N-isopropylacrylamide) were discussed in terms of cooperative units.