Synthesis, characterization, and swelling behaviors of wheat gluten/poly (sodium acrylate) porous composite hydrogel produced by yeast fermentation

Wheat gluten (WG) reacted with acrylic acid (AA) in the promotion of 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) to produce WG-AA chains. Following, yeast decomposed the starch that existed in WG to produce CO₂, which used as pore template to prepare a novel porous WG/poly(sodium acrylic)(PNaA) composite hydrogel(WG/PNaA) via free-radical graft copolymerization of sodium acrylate and WG-AA chains in the aqueous solution. FTIR spectra demonstrate that AA is grafted onto the WG chains, and the composite hydrogel is formed successfully in the presence of cross-linker N,N'-methylene discrylamide (MBA). Field emission SEM (FESEM) also displays that incorporating the proper amount of yeast into the hydrogel matrix can form porous interlinked channels within the composite hydrogel network. The porous WG/PNaA composite hydrogel shows greater equilibrium swelling capacity both in distilled water and in 0.9% NaCl solution, and the Schott's second-order swelling dynamic constant K_is is improved to 5 times compared with non-yeast exited hydrogel. Ritger's semi-empirical equation analysis also confirms that the water transport mechanism of the porous WG/PNaA composite hydrogel is non-Fickian diffusion type (n=0.5642), which means, the porous structure of the composite hydrogel is benefit to the water molecules spread quickly at the beginning swelling. The swelling-deswelling behaviors of the porous WG/PNaA composite hydrogel in distilled water-0.9% NaCl solution and in pH 2.2 and pH 7.4 phosphate buffer solution were assessed and the results show that the composite hydrogel exhibits excellent salt, pH-dependent swelling responsiveness after 5 times repeated swelling, which providing a potential application in the field of drug controlled-release.