University of Gothenberg and Chalmers University
Department of Chemistry
Location - Pancoe Auditorium
Hosted by Chad Mirkin
Electrochemical methods provide a powerful approach to investigate neurotransmitter release and storage from and in single cells. Additionally, the fly model (Drosophila melanogaster) provides a unique system to examine neurotransmitter release and drug dependence mechanisms in a small, but complete system. Mass spectrometry imaging with ion beams allows spatial resolution of a few micrometers to 50 nanometers in favorable cases. We have been using secondary ion mass spectrometry (SIMS) with a unique 40-kV argon cluster ion source and the NanoSIMS to measure the lipids across the fly brain and catecholamine in nanometer vesicles, respectively. Here, we have focused on the effect of a drug on lipid composition in the brain and on measuring transmitter in subregions of nanometer vesicles. Electrochemical cytometry is a new method we have developed to separate nanometer vesicles, lyse them on an electrode surface, and amperometrically detect the active contents of each vesicle in a high throughput manner. We began with a hybrid capillary-microfluidic device surrounding the electrode to rapidly determine levels of aminergic transmitters in vesicles. More recently, we have developed a new method of electrochemical cytometry to measure the total content of single neurotransmitter vesicles. The electrochemical response to single adrenal chromaffin vesicles filled with hormone transmitters as they impact a 33-um diameter disk-shaped carbon electrode will be shown. The vesicles appear to adsorb onto the electrode surface and sequentially spread out over the electrode surface trapping their contents against the electrode. These contents are then oxidized and a peak results for each vesicle that bursts. A large number of current transients can be observed if the concentration of vesicles is high relative to the area of the electrode. We have also been able to accomplish this type of cytometry in the cytoplasm of living PC12 and adrenal cells. Comparison of the contents of these biological vesicles to the release of catecholamine from single cells supports the concept that only a fraction of transmitter is released during exocytosis
Dr. Andrew Ewing is a Professor at Chalmers University of Technology and the University of Gothenburg, Sweden, and Honorary Professor at Beijing University of Science and Technology and Nanjing University of Science and Technology, China. He received his BS from St. Lawrence University and PhD from Indiana University. After his postdoctoral training at the University of North Carolina, he joined the faculty at Penn State University for 25 years, where he was Department Head in Chemistry and J. Lloyd Huck Chair in Natural Sciences. Dr. Ewing’s research focuses on the neuronal process of exocytosis. His group has pioneered small-volume chemical measurements at single cells, electrochemical detection for capillary electrophoresis, novel approaches for electrochemical imaging of single cells, and new electrochemical strategies to separate individual nanometer vesicles from cells and quantify their contents. They have also pioneered the development and application of mass spectrometry imaging for subcellular and neurochemical analysis. His nearly 300 publications have been cited approximately 14,500 times. Recently, he has received the Charles N. Reilley Award in Electroanalytical Chemistry, the American Chemical Society Award in Electrochemistry, the Norblad-Ekstrand Medal of the Swedish Chemical Society, and the SACP Analytical Chemistry Award. He is a member of the Gothenburg Academy of Arts and Sciences and the Royal Swedish Academy of Sciences, Chemistry Class and has supervised 48 PhDs and over 20 postdoctoral associates.