Functionalized anodic aluminum oxide (AAO) membranes for affinity protein separation

An ideal affinity membrane should own well uniformities. However, most existing microporous membranes used as affinity matrices generally have wide pore size distribution and some thickness variation. In this paper, chitosan (CS)-anodic aluminum oxide (AAO) composite membrane with excellent uniformities, such as narrow pore size and porosity distribution, as well as uniform membrane thickness, was fabricated, for the first time. Cu2+-attached affinity membrane was obtained by immobilizing Cu2+ on the CS-AAO membrane. The contents of CS and Cu2+ of affinity membranes were ∼49.7 and 27.15 mg/g membrane, respectively. The Cu2+-attached affinity membranes were used to recover a model protein, hemoglobin, from hemoglobin-phosphate solution (batch manner) and from the hemolysate (dynamic manner). The protein adsorption indicated that the adsorption capacity of hemoglobin was ∼17.5 mg/g membrane, and the adsorption isotherm fitted the Freundlich model well. Elution of protein showed desorption ratio was up to 91.2% using 0.5 M imidazole aqueous solution as the desorption agent. The adsorption capacities of all the tested affinity membranes did not significantly change during the repeated adsorption-desorption operations. The result of dynamic experiment showed Cu2+-attached affinity membranes can well purify the hemoglobin from the red cell lysate.