Fabrication and Characterization of DNA/QPVP‐Os Redox‐Active Multilayer Film

Abstract

Calf thymus DNA was immobilized on functionalized glassy carbon, gold and quartz substrates, respectively, by the layer-by-layer (LBL) assembly method with a polycation QPVP-Os, a quaternized poly(4-vinylpyridine) partially complexed with osmium bis(2,2'-bipyridine) as counterions. UV-visible absorption and surface plasmon resonance spectroscopy (SPR) showed that the resulting film was uniform with the average thickness 3.4 nm for one bilayer. Cyclic voltammetry (CV) showed that the total surface coverage of the polycations increases as each QPVP-Os/DNA bilayer added to the electrode surface, but the surface formal potential of Os-centered redox reaction shifts negatively, which is mainly attributed to the intercalation of redox-active complex to DNA chain. The electron transfer kinetics of electroactive QPVP-Os in the multilayer film was investigated by electrochemical impedance experiment for the first time. The permeability of Fe(CN) 3À 6 in the solution into the multilayer film depends on the number of bilayers in the film. It is worth noting that when the multilayer film is up to 4 bilayers, the CV curves of the multilayer films display the typical characteristic of a microelectrode array. The nanoporous structure of the multilayer film was further confirmed by the surface morphology analysis using atomic force microscopy (AFM).

Anion-Exchange-Based Amperometric Assay for Heparin Using Polyimidazolium as Synthetic Receptor

“…Figure B shows the typical CVs obtained at bare GC electrodes in 0.10 M PBS containing 1 mM Fe(CN) 6 3– . A pair of well-defined peaks was observed at +0.26 V (black curve), which was ascribed to the redox process of solution-phased Fe(CN) 6 3– . The addition of Pim into the Fe(CN) 6 3– solution results in an obvious decrease in the redox peak currents on the bare electrode (red curve), due to the formation of aggregation in the aqueous solutions, while the subsequent addition of heparin to this solution leads to the increase of peak currents (blue curve).…”

The rapid formation of functional monolayers on silicon under mild conditions

“…For strongly adsorbed electroactive species the relationship between the circuit elements (C dl , double-layer capacitance; C ads , adsorption pseudo-capacitance; R ct , charge transfer resistance) 73 of and the kinetic parameters characterizing a redox system has been described in the literature. [74][75][76][77][78] Using the refined R ct and C ads values, we obtained a k et value of 8 AE 2 s À1 . This value indicates ET kinetics that are comparable to that of aliphatic films 20 of comparable length.…”