Layer-by-Layer Self-Assembly of Glucose Oxidase with a Poly(allylamine)ferrocene Redox Mediator

Abstract

We report the redox mediation of glucose oxidase (GOx) in a self-assembled structure of cationic poly(allylamine) modified by ferrocene (PAA-Fc) and anionic GOx deposited electrostatically layer-by-layer on negatively charged alkanethiol-modified Au surfaces. Successive PAA-Fc and GOx layers were deposited by alternate immersion of the thiol-modified Au in the respective polyelectrolyte and enzyme solutions. The uptake of thiol, redox polymer, and GOx on the surface was monitored by quartz crystal microbalance. Cyclic voltammetry shows nearly ideal surface waves of ferrocene in the polymer with charge independent of sweep rate; the redox surface concentration was obtained from integration of the ferrocene/ferricinium voltammetric peaks. The redox charge increases in step with the number of PAA-Fc layers deposited. Enzyme catalysis for the oxidation of β-d-glucose was achieved with a multilayer PAA-Fc/GOx assembly, with each GOx layer contributing equally to the catalytic response. Only a small fraction of the active assembled GOx molecules are “electrically wired” by the ferrocene polymer although all of the enzyme could be oxidized by soluble ferrocenesulfonate when added to solution.

Long-range electron transport in Geobacter sulfurreducens biofilms is redox gradient-driven

“…Cyclic voltammetry (19,(34)(35)(36)(37) and spectroelectrochemical measurements (38)(39)(40)(41)(42)(43) of actively respiring Geobacter biofilms are consistent with long-range electron transport mediated by sequential electron transfer reactions through a network of bound redox cofactors comprised of ECM c-type cytochromes terminating with electron transfer to the anode surface. This proposed process, analogous to diffusive electron transport observed for redox polymers containing discrete redox moieties (20,(44)(45)(46)(47)(48), is an extension of the normal mode of electron transport in biological systems involving redox proteins (2) to longer length scales (up to 18 μm in the case of biofilms described here).…”

SERS in PAH-Os and gold nanoparticle self-assembled multilayers

“…The layer-by-layer ͑LbL͒ electrostatic adsorption deposition has become the prefered technique used to generate these self-assembled films due to a series of fundamental advantages: 4 ͑i͒ The different component ͑polymer, enzyme, or nanoparticle͒ concentrations can be better quantified during the deposition process, ͑ii͒ a well-defined spatial distribution of the components can be achieved and mass transport limitations can be minimized in nanometer-scale ultrathin films, ͑iii͒ the subnanometric geometry control also allows to generate a more directional and effective electronic transport than in disorder structures, and ͑iv͒ the self-assembled layer interdiffusion makes possible a true molecular wiring. Hodak et al 5 introduced redox enzymes deposited with a polycationic redox mediator in ordered multilayers using this technique and the redox mediation of glucose oxidase in self-assembled structures formed with the enzyme and poly͑allylamine͒ modified with Os͑byp͒ 2 ClPyCHO ͑PAH-Os͒ has been studied. 6,7 The assembly of derivatized gold nanoparticles with polyelectrolyte self-assembled multilayers has been studied by Song et al,8 in particular as regard the directional electron transport.…”

L-Proline sensor based on layer-by-layer immobilization of thermostable dye-linked L-proline dehydrogenase and polymerized mediator

“…Total iron content in the PAA polymer was estimated to be approxymately 20% spectrophotometrically at 440 nm using a calibration curve forferrocene carboxylic acid [24]. Both PAA-Fc and L-proDH were immobilized on Au electrode by LBL method.…”

“…The polymerized mediator was synthesized from poly(allylamine) and ferrocene carboxaldehyde according to the procedure reported by Hodak et al [24]. Eight milligrams ferrocene carboxaldehyde was dissolved in 5 ml methanol and added dropwise within 1 h to 30 ml of methanolic solution containing 40 mg poly(allylamine) and 0.26 ml triethylamine.…”

“…Various kinds of enzymes have been immobilized by LBL, and enzymes encapsulated in these integrated multilayer films showed superior chemical stability in long storage period and relative thermostability [22,23]. On the other hand, a biosensing system based on the alternated assembly of enzyme and polymerized mediator were developed, which made it possible to construct a reagentless sensor system [24][25][26][27][28]. In our previous work, LBL method has been used in the construction of a bienzyme biosensor [29].…”