Label-free electrochemical detection of enzymatic activity using peptide microarrays

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The sequencing of the human genome has provided a wealth of valuable information regarding the genetic basis of disease. However, the existence of a mere 30.000 human genes that encode an equal number of proteins cannot explain the complexity of human life and disease. Protein function is tightly regulated by a vast number of modifications and by interactions with other molecules. A comprehensive understanding of cellular function, in both healthy and diseased cells, requires knowledge of the functional state of proteins. Because enzymes are proteins with a crucial role in many physiological processes and diseases, the measurement of multiple enzymatic activities in biological samples and their correlation with cellular function can improve the understanding disease. Therefore, methods for the straightforward measurement of enzyme activity profiles are in high demand.In this project we will develop a new method for the measurement of multiple enzymatic activities simultaneously using microarrays. The new technology will rely on a simple and cheap detection method, label-free electrochemical spectroscopy, which will enable its application in the development of point-of-care diagnostics.In this project we will focus on proteases, enzymes that cleave the amide bonds of proteins (and shorter peptides). This process often leads to the activation or inactivation of the substrate proteins. Misregulation of protease activity is linked to many diseases such as cancer and cardiovascular disease. Furthermore, viruses such as HIV and Hepatitis C encode proteases that they use to successfully infect their hosts. Therefore, the measurement of specific protease activity profiles in biological samples such as blood may assist the early diagnosis of such diseases, and help monitor progress during treatment.The project will involve the synthesis of protease substrates and their immobilisation on gold electrodes. We will measure the cleavage of the immobilised substrates by electrochemical spectroscopy. Once the conditions for the electrochemical detection of protease activity have been established, we will immobilise a number of protease substrates on a microarray and measure multiple protease activities simultaneously. In future projects, this methodology will be used as the basis for microarray-based diagnostics that profile protease activities in biological samples (e.g., blood or cell lysates).