Influence of some amino acids on the dynamic swelling behavior of radiation-induced acrylamide hydrogel

The influence of some amino acids-alanine, glycine, valine, glutamine, hist idine, phenylalanine, and tryptophan-on the swelling behavior of acrylamide (AAm) hydrogel prepared by gamma-radiation was investigated. Swelling expe riments of AAm hydrogel were made in the universal buffer solutions and the amino acid solutions at certain pHs at 37 degrees C. These selected pH val ues were pK(1), pK(2) and isoelectric point (pI) values such as ionization of alpha-carboxyl groups, ionization of alpha-amino groups, and the pls of the amino acids, respectively. The swelling of AAm hydrogel increased when pH values of solutions were increased. The value of equilibrium swelling of AAm hydrogel in the solution of universal buffer was 880% at pH 10.0, wher eas it was 670% at pH 2.0. The values of equilibrium swelling of AAm hydrog el in amino acid solutions were between 830 and 965% at pH 10.0, whereas th ey were between 635 and 775% at pH 2.0. The rate constant of swelling, init ial swelling rate, theoretical maximum swelling, diffusional exponent, netw ork parameter, and diffusion coefficient were calculated by swelling kineti cs. Diffusions of the amino acid solutions into the hydrogel were generally found as non-Fickian in character. The diffusion coefficients of the hydro gel were between 0.91 x 10(-6) and 2.41 x 10(-6) cm(2)/s.