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Electrochemical characterization of globotriose-containing self-assembled monolayers on nanoporous gold and their binding of soybean agglutinin.

ABSTRACT: Self-assembled monolayers (SAMs) of ?-D-Gal-(1?4)-?-D-Gal-(1?4)-?-D-Glc-mercaptooctane (globotriose, Gb3-C8-SH) were prepared both as single-component SAMs and as mixed SAMs with either octanethiol (OCT) or 8-mercapto-3,6-dioxaoctanol (HO-PEG2-SH), on flat gold and on nanoporous gold (NPG) electrodes. The binding of soybean agglutinin (SBA) to the globotriose (Gb3) unit in the SAMs was then studied using electrochemical impedance spectroscopy (EIS), which is a label free method found to be quite sensitive to SAM composition and to the differences in SAM structure on NPG versus on flat Au. The affinity of SBA to the mixed SAM of HO-PEG2-SH and Gb3-C8-SH on NPG is found to be greater on NPG than on flat gold, and indicates a potential advantage for NPG as a substrate. The SAMs of HO-PEG2-SH were found to resist protein adsorption on either NPG or flat gold. The non-specific adsorption of SBA to OCT SAMs on flat Au was observed in EIS by the increase in charge transfer resistance; whereas, the increase seen on the NPG surface was smaller, and suggests that EIS measurements on NPG are less affected by non-specific protein adsorption. Atomic force microscopy (AFM) images of the SBA binding to mixed SAM of HO-PEG2-SH and Gb3-C8-SH on NPG showed a greater number of proteins on top of the OCT containing SAMs.

SUBMITTER: Pandey B

PROVIDER: S-EPMC3615452 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature

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Electrochemical characterization of globotriose-containing self-assembled monolayers on nanoporous gold and their binding of soybean agglutinin.

Pandey Binod B Tan Yih Horng YH Parameswar Archana R AR Pornsuriyasak Papapida P Demchenko Alexei V AV Stine Keith J KJ

Carbohydrate research 20121013

Self-assembled monolayers (SAMs) of α-D-Gal-(1→4)-β-D-Gal-(1→4)-β-D-Glc-mercaptooctane (globotriose, Gb3-C8-SH) were prepared both as single-component SAMs and as mixed SAMs with either octanethiol (OCT) or 8-mercapto-3,6-dioxaoctanol (HO-PEG2-SH), on flat gold and on nanoporous gold (NPG) electrodes. The binding of soybean agglutinin (SBA) to the globotriose (Gb3) unit in the SAMs was then studied using electrochemical impedance spectroscopy (EIS), which is a label free method found to be quite ...[more]

PMID: 23545324

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Project description:The background: The monolayers self-assembled on the gold electrode incorporated transition metal complexes can act both as receptor ("host" molecules) immobilization sites, as well as transducer for interface recognitions of "guest" molecules present in the aqueous solutions. Their electrochemical parameters influencing the sensing properties strongly depend on the transition metal complex structures. The objectives: The electrochemical characterization of the symmetric terpyridine-M2+-terpyridine and asymmetric dipyrromethene-M2+-terpyridine complexes modified with ssDNA probe covalently attached to the gold electrodes and exploring their ssDNA sensing ability were the main aims of the research presented. The methods: Two transition metal cations have been selected: Cu2+ and Co2+ for creation of redox-active monolayers. The electron transfer coefficients indicating the reversibility and electron transfer rate constant measuring kinetic of redox reactions have been determined for all SAMs studied using: Cyclic Voltammetry, Osteryoung Square-Wave Voltammetry, and Differential Pulse Voltammetry. All redox-active platforms have been applied for immobilization of ssDNA probe. Next, their sensing properties towards complementary DNA target have been explored electrochemically. The results: All SAMs studied were stable displaying quasi-reversible redox activity. The linear relationships between cathodic and anodic current vs. san rate were obtained for both symmetric and asymmetric SAMs incorporating Co2+ and Cu2+, indicating that oxidized and reduced redox sites are adsorbed on the electrode surface. The ssDNA sensing ability were observed in the fM concentration range. The low responses towards non-complementary ssDNA sequences provided evidences for sensors good selectivity. The conclusions: All redox-active SAMs modified with a ssDNA probe were suitable for sensing of ssDNA target, with very good sensitivity in fM range and very good selectivity. The detection limits obtained for SAMs incorporating Cu2+, both symmetric and asymmetric, were better in comparison to SAMs incorporating Co2+. Thus, selection of the right transition metal cation has stronger influence on ssDNA sensing ability, than complex structures.

Dataset Information

Electrochemical characterization of globotriose-containing self-assembled monolayers on nanoporous gold and their binding of soybean agglutinin.

Publications

Electrochemical characterization of globotriose-containing self-assembled monolayers on nanoporous gold and their binding of soybean agglutinin.

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