title: Enzyme-catalyzed bio-pumping of electrons into au-nanoparticles: a surface plasmon resonance and electrochemical study.
abstract: The enzyme glucose oxidase (GOx) is reconstituted on a flavin adenin dinucleotide (FAD, 1) cofactor-functionalized Au-nanoparticle (Au-NP), 1.4 nm, and the GOx/Au-NP hybrid is linked to a bulk Au-electrode by a short dithiol, 1,4-benzenedithiol (2), or a long dithiol, 1,9-nonanedithiol (3), monolayer. The reconstituted GOx/Au-NP hybrid system exhibits electrical communication between the enzyme redox cofactor and the Au-NP core. Because the thiol monolayers provide a barrier for electron tunneling, the electron transfer occurring upon the biocatalytic oxidation of glucose results in the Au-NPs charging. The charging of the Au-NPs alters the plasma frequency and the dielectric constant of the Au-NPs, thus leading to the changes of the dielectric constant of the interface. These are reflected in pronounced shifts of the plasmon angle, theta(P), in the surface plasmon resonance (SPR) spectra. As the biocatalytic charging phenomenon is controlled by the concentration of glucose, the changes in the theta(P) values correlate with the concentration of glucose. The biocatalytic charging process is characterized by following the differential capacitance of the GOx/Au-NP interface and by monitoring the potential generated on the bulk Au-electrode. The charging of the GOx/Au-NPs is also accomplished in the absence of glucose by the application of an external potential on the electrode, that resulted in similar plasmon angle shifts. The results allowed us to estimate the number of electrons stored per Au-NP at variable concentrations of glucose in the presence of the two different thiol linkers.
authors.affiliation: Institute of Chemistry, The Farkas Center for Light-induced Processes, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Oleg
authors.initials: O
authors.lastname: Lioubashevski
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Chegel
authors.forename: Fernando
authors.initials: F
authors.lastname: Patolsky
authors.forename: Eugenii
authors.initials: E
authors.lastname: Katz
authors.forename: Itamar
authors.initials: I
authors.lastname: Willner
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology; D002384:Catalysis; D004563:Electrochemistry; D004583:Electrons; D005949:Glucose Oxidase / Q000378:metabolism*; D006046:Gold / Q000737:chemistry* / Q000378:metabolism*; D015394:Molecular Structure; D036103:Nanotechnology; D010316:Particle Size; D020349:Surface Plasmon Resonance
chemical_list: D006046:Gold; D005949:Glucose Oxidase