Non-woven polymer membrane prepared by electrospinning technique is a potential material for affinity membrane application. In this work, electrospun polyacrylonitrile (PAN) nanofiber membranes were surface modified and studied as a novel affinity membrane, using bromelain as a research model. Firstly, chitosan (CS) was tethered onto the electrospun membrane surface to form a dual-layer biomimetic membrane through the use of glutaraldehyde (GA). The dye Cibacron Blue F3GA (CB) as a ligand was then covalently immobilized on the CS-coated membranes. The changes of chemical structures were characterized by element analysis, SEM, ATR-FT-IR and DSC. The content of CB attached onto the membrane was 370 mu mol/g membrane, and the CB-attached PAN nanofibers membrane showed a capturing capacity of 161.6 mg/g towards bromelain. The adsorption isotherm fitted the Freundlich model well. This work demonstrated that the electrospun PAN nanofiber membrane has potential for affinity membrane applications in wastewater treatment system. (C) 2010 Elsevier B.V. All rights reserved.