title: Stochastic sensing of single molecules in a nanofluidic electrochemical device.
abstract: We report the electrochemical detection of individual redox-active molecules as they freely diffuse in solution. Our approach is based on microfabricated nanofluidic devices, wherein repeated reduction and oxidation at two closely spaced electrodes yields a giant sensitivity gain. Single molecules entering and leaving the cavity are revealed as anticorrelated steps in the faradaic current measured simultaneously through the two electrodes. Cross-correlation analysis provides unequivocal evidence of single molecule sensitivity. We further find agreement with numerical simulations of the stochastic signals and analytical results for the distribution of residence times. This new detection capability can serve as a powerful alternative when fluorescent labeling is invasive or impossible. It further enables new fundamental (bio)electrochemical experiments, for example, localized detection of neurotransmitter release, studies of enzymes with redox-active products, and single-cell electrochemical assays. Finally, our lithography-based approach renders the devices suitable for integration in highly parallelized, all-electrical analysis systems.
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
authors.forename: Marcel A G
authors.initials: MA
authors.lastname: Zevenbergen
authors.forename: Pradyumna S
authors.initials: PS
authors.lastname: Singh
authors.forename: Edgar D
authors.initials: ED
authors.lastname: Goluch
authors.forename: Bernhard L
authors.initials: BL
authors.lastname: Wolfrum
authors.forename: Serge G
authors.initials: SG
authors.lastname: Lemay
mesh_terms: D000097:Acetonitriles / Q000737:chemistry*; D004563:Electrochemistry; D004566:Electrodes; D005296:Ferrous Compounds / Q000737:chemistry*; D000075163:Metallocenes; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods*; D010084:Oxidation-Reduction; D010316:Particle Size; D012996:Solutions; D013499:Surface Properties
chemical_list: D000097:Acetonitriles; D005296:Ferrous Compounds; D000075163:Metallocenes; D012996:Solutions; C004998:ferrocene; C032159:acetonitrile