Immobilization of Redox Enzymes on Nanoporous Gold Electrodes: Applications in Biofuel Cells

Abstract

Nanoporous gold (NPG) electrodes were prepared by dealloying sputtered gold:silver alloys. Electrodes of different thicknesses and pore sizes areas were prepared by varying the temperature and duration of the dealloying procedure; these were then used as supports for FAD‐dependent glucose dehydrogenase (GDH) (Glomorella cingulata) and bilirubin oxidase (BOx) (Myrothecium verrucaria). Glucose dehydrogenase was immobilized by drop‐casting a solution of the enzyme with an osmium redox polymer together with a crosslinked polymer, whereas bilirubin oxidase was attached covalently through carbodiimide coupling to a diazonium‐modified NPG electrode. The stability of the bilirubin‐oxidase‐modified NPG electrode was significantly improved in comparison with that of a planar gold electrode. Enzyme fuel cells were also prepared; the optimal response was obtained with a BOx‐modified NPG cathode (500 nm thickness) and a GDH‐modified anode (300 nm), which generated power densities of 17.5 and 7.0 μW cm−2 in phosphate‐buffered saline and artificial serum, respectively.

Controlling Redox Enzyme Orientation at Planar Electrodes

“…A few recently reported examples demonstrated the ability to transfer the determined molecular basis for DET from a planar to a more complex-structured electrode. The physicochemical properties of the SAM-modified gold electrodes obtained in the case of M. verrucaria BOD were transposed to functionalized nanoporous gold [197], as well as to functionalized carbon nanotubes films [30]. The requirement of an aromatic linker to anchor LAC via the Cu T1 was confirmed on films made of gold nanoparticles [198].…”

Rational Design of Enzyme‐Modified Electrodes for Optimized Bioelectrocatalytic Activity

“…In the last decades, numerous strategies have been proposed to immobilize BOD on various electrodes allowing efficient DET . To name a few, DET was achieved by BOD adsorption on electrodes functionalized with carboxyl groups, or by pulse‐assisted techniques . In all these cases, the electron transfer between enzyme and electrode was facilitated compared to conventional adsorption, but in order to increase the stability of such an electroenzymatic device, it is preferable to immobilize BOD by using covalent binding.…”

Tackling the Challenges of Enzymatic (Bio)Fuel Cells

“…Moreover, the confinement effects of the porous electrodes are of advantage in the efficient coupling of enzymes 282,283 and redox polymers modified surface 283 , in comparison to planar electrodes ( Figure 7). Porous gold electrodes featuring good electrical conductivity, chemical stability and biocompatibility can be fabricated by dealloying 282,284,285 , Au nanoparticle (AuNP) assembly 75,[286][287][288][289] , anodization 290 , or hard- [291][292][293] and soft-294 template methods.…”

“…An optimal DET current for BOD was observed on porous gold electrodes with a pore size of ca. 20 nm which was large enough to accommodate the enzyme while providing a high surface area for sufficient enzyme loading 283 .…”

“…The self-charged system achieved a P max of 608 μW cm -2 when the capacitor was discharged, 90% higher than the value for series-connected EFCs. In the discharge step, the accumulated charge can be released at a fixed resistance 384 or current density 283 . Based on such a methodology, Kizling 364 , which could be self-charged and discharged by a range of current densities as high as 4 mA cm -2 for 0.01 s with a P max of 0.87 mW cm -2 (absolute maximum power: 10.6 mW), 10 times higher than that of the EFC itself.…”