Bioelectrocatalysis of Fructose Dehydrogenase at Polyanilline-Modified Electrodes

Polymers can provide a suitable chemical environment for the immobilization of biomolecules in an active form on surfaces. Furthermore they can be used to wire redox proteins and enzymes with electrodes. For this purpose mainly redox polymers with well-defined redox centres and conductive polymers with intrinsic electron conductivity are applied. Polyanillines are belonging the latter class of polymers. Their properties can be easily tuned by the substitution pattern on the monomeric units. Recently we have shown that sulfonated polyanillines are suitable partners in the interaction with the enzyme PQQ-dependent glucose dehydrogenase [1]. On the basis of efficient electron exchange  different enzyme electrodes can be constructed [2-4].

In this study we have investigated whether it is possible to connect the multi-domain enzyme fructose dehydrogenase FDH with electrodes using the same group of polymers. The interaction of a sulfonated and methoxy-substituted polyanilline with FDH is studied in solution using UV/Vis spectroscopy. It can be demonstrated that electron transfer from the substrate reduced enzyme to the polymer is feasible, but also that this interaction is enhanced by the presence of calcium ions. Subsequently the reaction has been investigated by electrochemical means with all partners in solution verifying the spectroscopic results. In a next step of development the enzyme has been fixed on planar ITO electrodes by means of a polymer layer. Such an enzyme electrode exhibits effective, substrate-induced bioelectrocatalysis starting at rather low potential (~0mV vs Ag/AgCl). The efficiency can be significantly enhanced when macroporous ITO electrodes are used. They have pore size diameters of ~ 300nm and allow incorporation of higher amounts of polymer and enzyme. A current enhancement of ~ 35 is found compared to the flat ITO. The study demonstrates that sulfonated polyanillines can be considered as valuable matrices in connecting redox enzymes with electrodes.

[1] D. Sarauli; C.G. Xu; B. Dietzel; B. Schulz; F. Lisdat,  Acta Biomater. 2013, 9, 8290

[2] I. Schubart; G. Göbel; F. Lisdat,  Electrochimica Acta 2012, 82, 224

[3] D. Sarauli, C.G. Xu, B. Dietzel, B. Schulz, F. Lisdat, Journal of Materials Chemistry B 2 (21) 2014 3151-3404

[4] D. Sarauli, K. Peters, Xu, B. Schulz, D. Fattakhova-Rohlfing, F. Lisdat, ACS Appl. Mater. Interfaces 2014, 6, 17887