title: In situ Observation of Direct Electron Transfer Reaction of Cytochrome c Immobilized on ITO Electrode Modified with 11-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}undecylphosphonic Acid Self-assembled Monolayer Film by Electrochemical Slab Optical Waveguide Spectroscopy.
abstract: To immobilize cytochrome c (cyt.c) on an ITO electrode while keeping its direct electron transfer (DET) functionality, the ITO electrode surface was modified with 11-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}undecylphosphonic acid (CH3O (CH2CH2O)3C11H22PO(OH)2, M-EG3-UPA) self-assembled monolayer (SAM) film. After a 100-times washing process to exchange a phosphate buffer saline solution surrounding cyt.c and ITO electrode to a fresh one, an in situ observation of visible absorption spectral change with slab optical waveguide (SOWG) spectroscopy showed that 87.7% of the cyt.c adsorbed on the M-EG3-UPA modified ITO electrode remained on the ITO electrode. The SOWG absorption spectra corresponding to oxidized and reduced cyt.c were observed with setting the ITO electrode potential at 0.3 and -0.3 V vs. Ag/AgCl, respectively, while probing the DET reaction between cyt.c and ITO electrode occurred. The amount of cyt.c was evaluated to be about 19.4% of a monolayer coverage based on the coulomb amount in oxidation and reduction peaks on cyclic voltammetry (CV) data. The CV peak current maintained to be 83.4% compared with the initial value for a M-EG3-UPA modified ITO electrode after 60 min continuous scan with 0.1 V/s between 0.3 and -0.3 V vs. Ag/AgCl.
authors.affiliation: Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Matsuda
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Okabe
authors.forename: Ayako
authors.initials: A
authors.lastname: Omura
authors.forename: Miki
authors.initials: M
authors.lastname: Nakano
authors.forename: Koji
authors.initials: K
authors.lastname: Miyake
mesh_terms: D000327:Adsorption; D000818:Animals; D045304:Cytochromes c / Q000737:chemistry*; D004563:Electrochemistry; D004566:Electrodes; D004579:Electron Transport; D004800:Enzymes, Immobilized / Q000737:chemistry*; D010757:Phosphorous Acids / Q000737:chemistry*; D013057:Spectrum Analysis; D017971:Tin Compounds / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D010757:Phosphorous Acids; D017971:Tin Compounds; C570063:phosphonic acid; C109984:indium tin oxide; D045304:Cytochromes c