Characterizing functionalized electrode surfaces with unique spectroelectrochemical methods for biosensor development

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Electrochemical processes form the basis of many new technologies (eg. batteries, fuel cells, solar cells) as well as approaches to bioanalytical sensing. The portability and small footprint of these sensors Electrochemical based biosensors rely on the modification of the electrode surface with biologically active species (eg lipids, nucleic acids or enzymes) that can specifically interact with compounds of interest in the sample, and then transduce this interaction into a signal that can be measured accurately. This requires a high level of control over the preparation of the sensor surface. A biosensor must have a sufficient number of probes on the surface which are accessible by the targets in solution so that when specifically interacting, will create a change in the measured signal. Controlling the probe density, probe distribution, reducing the non-specific interactions (noise) by controlling the surface structures will enable improvement of the functionalized surfaces with extension to development of new biosensor transduction motifs. Characterizing the electrochemical interface has been the focus of our research efforts for many years. We have developed a unique in-situ fluorescence microscopic method for analyzing these interfaces while controlling the electrochemical potential. This is accomplished by using a fluorophore labelled adsorbate. The fluorescence measured depends on the separation of the fluorophore from the electrode surface with fluorescence quenched when closer than 5nm. Our method enables a detailed understanding of the structure of these modified surfaces, from large scales (sub mm) to molecular sized regimes (10s of nm) and how this depends on the surface crystallography and the functionalization method (multiple step adsorption, co-adsorption, potential-controlled adsorption, chemical modification of the functionalized surface). We continue to advance our in-situ characterization method to include confocal microscopy with fluorescence lifetime imaging. These new analysis methods will be used in creating complex surfaces; from multi-component surfaces, to quantum dot decorated surfaces. Our long term goal is to devise methods for creating biosensor surfaces which are optimally functional guided by the use of advanced in-situ characterization techniques. This is the foundational principle which we will use to influence the creation of well defined biosensors and, more broadly all types of functionalized surfaces.