Spectroelectrochemical sensing of tris (2,2 bipyridyl) ruthenium (II) dichloride hexahydrate in low ionic strength samples and the spectroelectrochemical characterization of aeruginosin A

The need for sensors that can be used to selectively detect analytes in the presence of direct interferences cannot be over emphasized. Thus, the first part of this dissertation focuses on spectroelectrochemically sensing tris (2,2 bipyridyl) ruthenium (II) dichloride hexahydrate ([Ru(bpy) 3]2+)---a model analyte, in low ionic strength samples containing other 'multiple ions'. Spectroelectrochemical sensors used in this research are rugged and highly selective to the analyte of interest and possess three modes of selectivity in one device. First, the analyte partitions into a charge-selective film which is coated on an indium tin oxide (ITO) optically transparent electrode. At the electrode surface, reversible electrochemistry at a specific potential window for the analyte is initiated resulting in one redox form absorbing light at a specific wavelength and the other form non-absorbing. The amount of analyte trapped in the film is measured by attenuated total reflection absorbance spectroscopy for optical detection. In the course of this study, the extent of ion-exchange competition occurring between the analyte and ions of supporting electrolyte and how this competition ultimately affects the sensor's signal was determined. The spectroelectrochemical sensor's high point is its selectivity and this property was proven in detecting [Ru(bpy) 3]2+ in natural (Hanford, WA well water and Bothell, WA river water) and treated water (Cincinnati, OH tap water) samples. Calibration curves were obtained for [Ru(bpy)3]2+ in well, river and tap water with detection limits of 108, 139 and 264 nm, respectively. A standard addition method was employed to determine the concentration of [Ru(bpy) 3]2+ spiked in the Hanford well water. The unknown concentration of [Ru(bpy)3]2+ determined by spectroelectrochemical experiments was 0.39 +/- 0.03 microM versus the actual concentration of 0.40 microM. Overall, the results from the spectroelectrochemistry with the water samples were very promising.;The second part of this dissertation was based on a collaboration with the UC sensors group and Dr. Daniel J. Hassett and Dr. Shengchang Su (Department of Molecular Genetics, Biochemistry and Microbiology at the College of Medicine, University of Cincinnati), Dr. Raymond E. Boissy and Amanda Greatens (Department of Dermatology at the College of Medicine, University of Cincinnati) and Dr. Larry Sallans (Center for Mass Spectrometry, Department of Chemistry, University of Cincinnati).;Pseudomonas aeruginosa bacteria produces multiple pigments during routine in vitro culture and in vivo during colonization of burn wounds and in the airways of cystic fibrosis (CF) patients. This study determined the redox, spectroelectrochemical and biological characterization of aeruginosin A, one of the secreted pigments. Results from this study show that aeruginosin A exhibits reversible electrochemistry, and its spectroelectrochemistry show that its strongest fluorescence is seen in its parent or oxidized form. However, it was discovered that aeruginosin A has no adverse effects on Staphylococcus aureus, Escherichia coli or human keratinocytes.