Layer-by-layer electrochemical biosensor with aptamer-appended active polyelectrolyte multilayer for sensitive protein determination

Herein, we report two simple label-free electrochemical aptasensors for protein detection using layer-by-layer (LBL) self-assembled multilayers with ferrocene-appended poly(ethyleneimine) (Fc-PEI), carbon nanotubes (CNTs) and aptamer. In one sensing strategy, the Fc-PEI, CNTs and DNA aptamer are LBL assembled on the electrode surface via electrostatic interaction. In the presence of target, the aptamer on the outermost layer of the LBL self-assembled multilayer would catch the target on the electrode interface, which makes a barrier for electrons and inhibits the electro-transfer, resulting in the decreased DPV signals of Fc-PEI. Using this strategy, a wide detection range (0.3-165 ng ml(-1)) for model target thrombin is obtained, with a low detection limit of 0.14 ng ml(-1). In the similar sensing strategy for detection of lysozyme, a wide detection range (0.2 ng ml(-1) to 1.66 mu g ml(-1)) and a low detection limit (0.17 ng ml(-1)) are obtained. These results prove that the LBL sensing strategies developed possess sensitivity, selectivity, stability and generality. (c) 2010 Elsevier B.V. All rights reserved.