Metal-based Chemosensors for Carbohydrates and Biologically Important Ligands

Chemosensors based on indicator displacement were developed for the optical detection of different analytes in aqueous solution. The sensing of carbohydrates, including glucose, in aqueous solution at pH 7.4 was achieved by a fluorescent indicator displacement assay (IDA) based on a palladium complex. The assay is easy to perform as it just requires mixing of a commercially available dye and a simple Pd complex. The sensitivity of the assay is similar to what is typically found for boronic acid-based systems, but its selectivity profile towards different carbohydrates is quite distinct. Furthermore the same complex was employed for the successful differentiation of various diols. A palladium-based sensor is a novelty as almost all carbohydrate sensors exclusively utilize boronic acids as binding site. Various palladium complexes were evaluated and the usability for carbohydrate sensing was found to be strongly dependent on the ligands. Ruthenium-arene complexes are known to have potent anticancer properties. There is an interest in a quick and simple method to give information about the stability towards ligand exchange of these complexes in aqueous solutions. Indicator displacement assays, which can give information about the binding strength of different ligands to a ruthenium-arene complex, were investigated in water at pH 7.4. Various biomolecules (different amino acids, maltol etc.) could be differentiated by a colorimetric (naked eye) IDA. Additionally, a correlation between the binding strength of the bidentate ligand and the amount of indicator displaced was found. Matrix metalloproteinase (MMPs) are endoproteinases and their dysfunction can result in various health problems (e.g. arthritis). In order to provide a quick and simple tool for the evaluation of new MMP inhibitors, colorimetric IDAs were developed. For calibration of the system, MMP inhibitors were synthesized and their IC50 values for different MMP isoforms determined. Although the new MMP inhibitors have very similar structures a differentiation by an indicator displacement array was achieved. The IC50 values were, with a couple exceptions, rather high and similar. None of the new MMP inhibitors exhibited specific inhibition of one of the studied MMP isoforms.