In situ electrodepo sited nanoparticles for facilitating electron transfer across self-assembled monolayers in biosensor design

Gold nanoparticles (AuNPs) were synthesized in situ and electrodeposited onto An substrate. The AuNPs modified interface facilitates electron transfer across self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA). After activation of surface carboxyl groups with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide, the interface displayed good stability for immobilization of biomolecules. These modification processes were characterized by contact angle measurement, cyclic voltammetry and electrochemical impedance spectra. The immobilized acetyleholinesterase (AChE), as a model, showed excellent activity to its substrate, leading to a stable AChE biosensor. Under the optimal experimental conditions, the inhibition of malathion on AChE biosensor was proportional to its concentration in two ranges, from 0.001 to 0.1 mu g mL(-1) and from 0.1 to 25 mu g mL(-1), with detection limit of 0.001 mu g mL(-1). The simple method showed good reproducibility and acceptable stability, which had potential application in biosensor design. (c) 2007 Elsevier B.V. All rights reserved.