A sandwich-type electrochemical immunosensor for the ultrasensitive detection of the salbutamol (SAL) antigen based on sodium dodecylbenzene sulfonate-functionalized graphene sheets (SDBS-GS), Pd nanoparticles in functionalizecl SBA-15 (Pd@SBA-15) and ionic liquid (IL) is described. The primary SAL antibody (Ab(1)) can be covalently attached to the sulfonic groups of SOBS-GS through the amines of Ab(1) with an acyl chloride cross-linking reaction. Pd@SBA-15 was prepared by adsorption of H2PdCl4 onto the SBA-15 surface; the adsorbed H2PdCl4 was then reduced to Pd nanoparticles with sodium borohydride. Pd@SBA-15 was conjugated to the secondary SAL antibody (Ab(2)) through glutaraldehyde. IL was added to the mixture of Pd@SBA-15 and Ab(2) to promote electron transport. The synergistic effect between IL and Pd@SBA-15 retained the bioactivity of Ab(2). The sensitivity of the sandwich-type immunosensor using Pd@SBA-15/Ab(2)/IL for the detection of SAL was much higher than those that used either SBA-15/Ab(2) or Pd@SBA-15/Ab(2). Under optimal conditions, the electrochemical immunosensor exhibited a wide working range from 0.02 to 15.0 ng/mL with a detection limit of 7 pg/mL. The precision, reproducibility and stability of the immunosensor were acceptable. The proposed strategy could be easily extended to fabricate immunosensors for other tumor markers. (C) 2012 Elsevier Ltd. All rights reserved.