In-situ study of electrochemical interfaces modified by adsorbed organic molecules; characterizing heterogeneous adsorbate coverage with application to biosensors

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In-situ characterization of electrochemical surfaces modified by adsorbed organic molecules is accomplished using a number of different approaches. We have developed a unique method that combines fluorescence microscopy and electrochemistry. This method is proving useful for characterizing the heterogeneity of surface coating, enabling the study of these surfaces with more detail thereby raising some important questions. The creation of advanced biosensors relies on the modification of surfaces to provide a functional interface that can sense the analyte in solution. A number of interesting motifs have been developed that rely upon the orientation of the adsorbed molecules on the sensor surface. These molecules (eg DNA) can include redox active moieties that provide a simple electrochemical signal (current) that can be used for signal transduction. In some cases, the current decreases upon binding, and this has been observed in buffers and complex media. Recent studies of the DNA modified gold surface with our in-situ fluorescence microscopic method has revealed that these surface, created following current literature procedures, are not homogeneous and are, in fact quite heterogeneous. This surprising result has resulted in a number of questions that this research proposal aims to answer. Are these surfaces as presented in simplified cartoons? Does our method highlight these imperfections, something that is hard to determine using the current analytical methods? Can we change the procedures used to make these sensors to eliminate or minimize these undesirable features? In collaboration with two electrochemical research groups in Europe, we will expand the types of molecules that we will assemble onto the electrode surface (aptamers, peptides, DNA). We aim to understand these sensor surfaces and with our unique in-situ characterization tool, determine the characteristics of the system that contribute to these heterogeneous regions, and assess the impact on sensor response. We also intend to use this method to continue our studies into creating a model of a biomembrane supported on an electrode, and to investigate the nature of the forces that govern the movement of molecules that are electrochemically desorbed.