A MEMS based amperometric detector for E-Coli bacteria using self-assembled monolayers

We developed a system for amperometric detection of Escherichia coli (E. co li) based on the integration of microelectromechanical systems (MEMS), self -assembled monolayers (SAMS), DNA hybridization, and enzyme amplification. Using MEMS technology, a detector array was fabricated which has multiple e lectrodes deposited on a Si wafer and was fully reusable. Using SAMs, a mon olayer of the protein streptavidin was immobilized on the working electrode (Au) surface to capture rRNA from E. coli. Three different approaches can be used to immobilize streptavidin onto Au, direct adsorption of the protei n on bare Au, binding the protein to a biotinylated thiol SAM on Au, and bi nding the protein to a biotinylated disulfide monolayer on Au. The biotinyl ated thiol approach yielded the best results. High specificity for E. coli was achieved using ssDNA-rRNA hybridization and high sensitivity was achiev ed using enzymatic amplification with peroxidase as the enzyme. The analysi s protocol can be conducted with solution volumes on the order of a few mic roliters and completed in 40 min. The detection system was capable of detec ting 1000 E. coli cells without polymerase chain reaction with high specifi city for E. coli vs. the bacteria Bordetella bronchiseptica. (C) 2001 Elsev ier Science B.V. All rights reserved.