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An electrochemical molecular beacon aptasensor for fast and sensitive assay of thrombin is developed and characterized. A bifunctional derivative of the thrombin‐binding aptamer, 15‐base long with a redox‐active ferrocene moiety and a pendant hexanethiol linker group at the termini of the aptamer strand was immobilized on Au electrode surface. The electrochemical behavior of the aptasensor was studied using cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), square‐wave voltammetry (SWV) and chronopotentiometric stripping analysis (PSA) techniques. Taken together, these experiments support the switch “on” mechanism of the system when the thrombin binds to the immobilized aptamer. The variation of response to the concentration of thrombin, the target protein, was evaluated by square‐wave voltammetry and chronopotentiometric stripping analysis in HEPES buffer solution (pH 8.0, 0.01 M). The aptasensor showed a specific response to thrombin in the range 1.0 to 35 nM with a detection limit of subnanomolar level concentrations. The reaction time, reproducibility, specificity and stability of the aptasensor were also studied.

Self‐assembled monolayers (SAM) were obtained on gold electrodes using thioctic esters of benzo[1,3]dioxinol. These SAMs present a group that can be electroactivated selectively and was used for the directed, reagentless, covalent patterning of proteins. The advantage of this moiety is that it allows electroactivation at low potentials increasing selectivity and reliability. In this study, the efficiency of this patterning system is examined. Cyclic voltammetry (CV) was used to confirm the electroactive nature of SAM modified electrodes, showing fast and complete electrochemical deprotection with one scan. The enzymes glucose oxidase (GOx) and horseradish peroxidase (HRP) were patterned on the SAM‐modified electrode through Schiff's base formation after electrochemical deprotection, confirming the selective nature of the electroactive substrate. Amperometric response was measured after the GOx immobilization showing high selective response. Real time monitoring is shown by immobilization of HRP on the SAM modified surface using electrochemical surface plasmon resonance (ESPR) after electrochemical deprotection, again showing high selective response when compared to the protected control.

An amperometric immunosensor for the detection of the herbicide atrazine has been developed. A redox polymer PVPOs(bpy)2Cl was co‐immobilized with the specific antibody on the surface of the electrode by crosslinking with PEGDGE to form an electron‐conducting hydrogel. In a competitive assay the occurrence of the antibody–antigen reaction on the surface of the sensing film was detected through the ‘electrical wiring’ of the redox centres of antigen‐labelled horseradish peroxidase and the electrode surface in the presence of H2O2at 0.1 V (vsAg/AgCl). Copyright © 1998 John Wiley & Sons, Ltd.

Glucose electrodes based on hydrogels made by crosslinking glucose oxidase and the redox polymer formed upon complexing polyvinyl imidazole (PVI) with [Os(dmo-bpy)2Cl]+/2+(dmo-bpy= 4,4′-dimethoxy-2,2′-bipyridine) on vitreous carbon electrode surfaces were investigated. The redox potential of the hydrogels was −69 mV (SCE) and their glucose electrooxidation current reached a plateau at +50 mV (SCE). Urate and acetaminophen were not electrooxidized at this potential at rates that would interfere with the glucose assays. At 32 mM glucose concentration switching of the atmosphere from argon to O2reduced the current only by 5%.