Synthesis and characterization of pH-and salt-sensitive hydrogel based on chemically modified poultry feather protein isolate

Hydrogels were synthesized from poultry feather protein by crosslinking ethylene diamine tetraacetic dianhydride (EDTAD)-modified feather protein isolate (FPI) with glutaraldehyde (Glu). Different molar ratios of EDTAD/FPI were used to obtain FPI of different degrees of acylate modification. Differential scanning calorimeter measurements of glass transition temperature suggested that hydrogel formation was based on the hydrogen bond between EDTAD-modified FPI segments. The swelling properties of modified FPI hydrogel were investigated in deionized water and in solutions of different salt contents (i.e., ionic strengths) and pH. An optimal swelling ratio (SR) of 63 g/g was obtained when molar ratios of EDTAD/FPI and Glu/FPI were 0.12 and 0.008, respectively. SR decreased substantially with increase in ionic strength, and at a given ionic strength, SR increased with solution pH in 4.0 to 10.0 range. The water transport mechanism of the hydrogel was also pH dependent and was controlled by Fickian diffusion and polymer relaxation. At higher pH value, the water transport profile became more dependent on polymer relaxation than at lower pH. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010