RUI: Selenium-modified Electrodes: From Surface Reactivity to Biosensing Developments

Barnard College, New York NY

Investigators

Abstract

With support from the Chemical Measurement and Imaging program in the Division of Chemistry, Professor Marisa Buzzeo of Barnard College and her team of undergraduate research students study how biological molecules communicate via the transfer of electrons. The tunable chemical reactivity that is accessible by the transfer of electrons is harnessed by Nature in a wide range of important biochemical processes. Photosynthesis and cellular respiration, for example, rely on the exquisite sensitivity and selectivity with which electrons are transferred between molecules. The Buzzeo group is focusing on the chemical properties of the essential trace element selenium, a natural antioxidant, to gain a deeper understanding of its unique role in biological electron transfer events. Their studies provide fundamental information regarding the reactivity distinctly afforded by the presence of this element. Findings from their work also have the potential to result in selective sensing of selenium- and sulfur-containing molecules, including in clinical settings. This project provides multiple interdisciplinary research opportunities for students at Barnard College, a liberal arts undergraduate institution for women, and bolsters the participation of underrepresented groups in the physical sciences via community-based outreach activities involving high school students from disadvantaged backgrounds and individuals with disabilities. The aim is to expose both groups to chemical concepts, applications, and careers that would otherwise appear unattainable or inaccessible. The accurate measurement of redox potentials is imperative for detailed understanding of how species participate in electron-transfer reactions. Electrochemical studies of chalcogen-containing molecules are hindered by unwanted oxidation and adsorption on electrode surfaces. New electrode materials have been identified that demonstrate great promise for the aqueous measurement of chalcogen-containing redox-active molecules. It has been shown that the intrinsic reactivity between selenium and gold yields a stable and reproducible electrode surface modification that makes accessible diffusional electron transfer of solution-based chalcogen analytes. The Buzzeo group is working to characterize selenium-modified electrodes by a combination of spectroscopic and electrochemical techniques. Specifically, they are measuring the electrochemical behavior of biological selenium and sulfur species on selenium-modified gold substrates to obtain fundamental thermodynamic parameters, and using the optimized selenium-modified surfaces to develop a portable electrochemical biosensor for cystine, a known culprit in kidney stone formation. Aided by collaborations across several departments and institutions, the work entails characterization of both surface and solution speciation to build a molecular-level description of the selenium-gold adsorbate layer. Sensing capabilities are assessed through comprehensive electroanalytical study of selenium- and sulfur-containing amino acids, peptides, and ligands. Together these pursuits will yield fundamental knowledge about selenium-gold surface reactivity and will enable measurement of physiologically relevant redox-active species. The work offers Barnard undergraduates research training at the interface of physical, inorganic, analytical, and biological chemistry. Additionally, the work includes educational activities involving high school students from disadvantaged backgrounds and individuals with disabilities to promote a more diversified STEM workforce. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.