Monolayers of photosystem II on gold electrodes with enhanced sensor response—effect of porosity and protein layer arrangement

Abstract

Mass transport of the bulk of the analyte to the electrode and through the bioactive layer can be significantly improved by use of the nanoelectrode array and defined arrangement of protein film. This phenomenon has been studied by (i) atomic-force microscopy, (ii) electrochemical measurements of PSII activity, and (iii) digital simulations for an oriented monolayer of histidine-tagged photosystem II (PSII) immobilized on nitrilotriacetic acid (NTA)-modified gold electrodes. The output signal of the electrochemical biosensor is controlled by (i) mass transport from the bioactive layer to electrode and (ii) mass transport between the bulk of the analyte and the electrode. Mass transport through the bioactive layer was electrochemically studied for PSII self-assembled on gold screen-printed electrodes. A densely packed monolayer of PSII has a significant shielding effect toward the diffusion of redox mediator duroquinone (DQ). Mass transport to the planar electrode surface was improved by co-immobilization of bovine-serum albumin (BSA) as spacer biomolecule in the monolayer of PSII. Correlation between the electrochemical properties and surface arrangement of the resulting protein films was clearly observable and confirmed the improved mass-transport properties of structured enzyme monolayers. On the basis of this observation, the application of a bottom-up approach for improvement of electrode performance was proposed and digitally simulated for an infinite array of electrodes ranging in diameter from 50 nm to 5 microm. The nanoelectrode array, with the optimum time window selected for measurements, enables enhancement of mass transport between the bulk of the analyte and the macroelectrode by a factor of up to 50 in comparison with "classical" planar electrodes. Use of a time window enables minimization of crosstalk between individual electrodes in the array. The measurements require methods which suppress the double-layer capacity.

Recent advances in the electrochemistry and spectroelectrochemistry of membrane proteins

“…A major breakthrough in the electrochemistry of proteins was achieved with the report of glucose oxidase ' nanowiring ' onto an electrode covered with a monolayer of gold nanoparticles (Xiao et al, 2003), which clearly demonstrated that the gold NPs, thanks to their small size, can mediate the long-range electron-transfer between the electrode and the enzyme cofactors. Gold NPs have thus started to be examined as supports for membrane proteins in particular photosystems for sensing applications (Maly et al , 2005 ;Miyachi et al , 2010 ). In a preliminary study, our group has shown that gold NPs constitute an efficient support for the immobilization of several respiratory membrane proteins fragments from the thermophilic bacterium Thermus thermophilus (Meyer et al , 2011 ).…”

Photoelectron Generation by Photosystem II Core Complexes Tethered to Gold Surfaces

“…sors [9][10][11][12] and as components of a future biohydrogen production device. [13] Hydrogen generation through solid-state integration of PSII and PSI RCs with hydrogenases has been suggested, although a full device has yet to be assembled.…”

Photobioelectrochemistry: Solar Energy Conversion and Biofuel Production with Photosynthetic Catalysts

“…When they included bovine serum albumin (BSA) in the enzyme mixture during immobilization, the photocurrent increased to 108 nA/cm 2 after the BSA (which is only adsorbed) is washed away from the surface. 58 In 2008, researchers in Japan used the same immobilization technique on nanostructured Au electrodes and reported a photocurrent of 2.44 μA/cm 2 with no added mediator. 59 A very commonly used method for enzymatic electrodes is tethering with a redox polymer.…”