Adsorptive membranes have shown great promise for bioseparations as an alternative to packed bed chromatography. Here we evaluate an adsorptive membrane (felt) made from electrospun cellulose acetate nanofibers as an ion-exchange medium for protein separations. The as-electrospun cellulose acetate nanofibers had diameters ranging from tens of nanometers to microns, and the pore sizes within the nanofiber felts were in the range from sub-microns to microns. The cellulose acetate nanofibers were hydrolyzed/deacetylated to yield regenerated cellulose nanofibers, which were then surface functionalized with diethylaminoethyl (DEAE) anion-exchange ligand. SEM imaging, along with FT-IR spectroscopy, and nitrogen content analysis were used to follow each stage of the process. For comparison, a regenerated cellulose microfiber adsorption medium, a commercially available regenerated cellulose adsorptive membrane, and bleached absorbent cotton balls, were all similarly treated and evaluated. The results indicated that the functionalized nanofiber felt had the highest static binding capacity of 40.0 mg/g for bovine serum albumin (BSA), compared to 33.5 mg/g, 14.5 mg/g, and 15.5 mg/g for the functionalized commercial membrane, cellulose microfiber medium, and cotton balls, respectively; and the DEAE nanofiber felt had over five times higher permeability of 10 mM Tris buffer, pH 8.0 than the DEAE commercial membrane. It was also found that detrimental system dispersion, as determined by calculation of the Peclet number, could be limited by increasing the number of felt layers used for the adsorption bed, without compromising pressure limitations. Dynamic adsorption of BSA, at 10% breakthrough, was higher for the DEAE nanofiber felt (26.9 mg/g) compared to the DEAE commercial membrane (20.9 mg/g). (C) 2008 Elsevier B.V. All rights reserved.