Photo-Induced Signal Chains at Enzyme Electrodes

Abstract

During the last decade photoelectrochemical devices which couple biochemical reactions to light-sensitive electrodes have gained increasing research interest. These kind of light-triggered systems have the inherent advantage that an additional tool - the light - can be used to control the reactions at a sensing electrode. This allows a light-directed read-out, but can also be used to change the energetic situation on the surface resulting in advantageous potential behavior [1].Enzymes as biocatalysts provide the advantage of a catalytic analyte conversion and specificity in this reaction. In order to couple them to light-sensitive electrodes different approaches have used.Besides the use of co-substrates or products [2], we have been focusing on the use of mediators for this interaction [3] or the establishment of a direct electron transfer of the enzyme to the light- sensitive entity [4]. Here we report on the use of two different types of polymers for establishing the electrical contact.In order to exploit the advantages of a high surface area we have constructed 3D electrodes which can be rather easily prepared by a template approach combined with spin coating as deposition method..Thus, the thickness of the electrode structure can be adjusted in a defined way [5,6].In a first approach 3D TiO2 of inverse opal character has been sensitized by a conducting polymer – sulfonated polyaniline. The polymer has here two functions: It ensures the light sensitivity in the visible range and also provides an interface at which the enzyme can exchange electrons. Advantageously the current signal can be gained at rather low potential. Furthermore, the response can be tuned by the dimensions of the 3D electrode demonstrating the scalability of the approach.As a further advancement we have used a redox polymer in order to couple FAD-dependent glucose dehydrogenase to the electrode. Here PbS QDs have been generated directly onto a 3D TiO2 electrode and characterized by TEM and photoelectrochemistry. The system allows the generation of a defined anodic photocurrent, which can be significantly enhanced by the biocatalytic conversion of glucose. Here the substrate dependent current signal starts at about -054V vs Ag/AgCl.Such electrode systems can find application in light-triggered sensing, but also for bioenergetics since the photocatalytic process can be “feeded” by electrons from the biocatalytic conversion.