A novel TiO2-densified cellulose beads as the matrix used in expanded beds were exploited. The matrix was activated by epichlorohydrin and then coupled with diethylamine to function as an anion exchanger for the adsorption of proteins. Several factors influenced the efficiency of activation, such as the amount of epichlorohydrin, the concentration of NaOH, and the contents of TiO2 and cellulose in the matrix, were investigated. The optimal procedure for activation was found to be: mixing 20 g matrix beads in 40 mL 2.5 mol/L NaOH solution containing 8 mL epichlorohydrin for 8 h at 25 degreesC. The coupling efficiency of diethylamine with the activated matrix is close to 90% under the given conditions. The prepared adsorbent has favorable expanded bed characteristics and an accordant protein breakthrough behavior both in packed bed and in expanded bed, by possessing a dynamic adsorption capacity of 42.6 mg BSA/mL adsorbent at 10% breakthrough. The results demonstrated that the custom-made adsorbent can be applied to the expanded bed adsorption of proteins. (C) 2004 Published by Elsevier B.V.