Scanning Photoelectrochemical Microscopy and its Application to Biological Systems

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Electrochemistry with its ability to record currents in the femto-ampere range, which relates to only a few thousand electrons transferred per second in a redox process, represents an ideal tool to detect, monitor and quantify specific molecules interacting with a biological sample. Specialized micro- and nano-probes, such as micro-optical-ring (MOR) electrodes, consisting of optical fibers within an electrode sheath, allow localized irradiation and concurrent measurement of the electrochemical response of a sample. These probes have shown their usefulness in non-biological applications, but the opportunity no one has taken is the application of MOR electrodes to monitor radiation sensitive redox processes in biological systems on the micro- and nanoscale. The described program lies at the intersection of electrochemistry, analytical chemistry and biology and aims to better understand fundamental mechanisms related to the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in biological cells under various environmental conditions. Complex biological systems are often difficult to investigate electrochemically, due to the large number of electrochemically active substances. Using SPECM, redox reactions can be monitored by their spectroscopic signature to differentiate between electrochemical contributions from different species. Moreover, targeted stimulation of single biological entities is challenging to achieve. The specific local illumination of single biological cells through MOR electrodes while measuring their electrochemical response will provide fundamental insight into the radiation induced production of ROS/RNS. This research aims to better understand the time response and efficiency of cellular coping and reaction mechanisms in the presence of stimulants and inhibitors, such as antioxidants. Students emerging from this program will be equipped with multidisciplinary skills and a knowledge base to succeed in their future academic or industrial career endeavors.