Voltammetric behavior of selenocystine at modified gold substrates

Abstract

The voltammetric response of seleno-L-cystine has been studied at gold substrates under physiological conditions. The reactivity of diselenides is utilized to generate a modified electrode surface, which in turn allows for electroanalysis of solution-based selenium species. Stable and reproducible voltammetry is observed for selenocystine reduction at pH 7 on selenium-modified gold substrates (E mid =-486 mV vs. Ag/AgCl) and is consistent with a diffusionally controlled process. Modification of the gold surface is readily achieved via electrochemical cycling in the presence of a diselenide source at conventional scan rates. These studies afford voltammetric characterization of the selenocystine / selenocysteine redox couple under physiologically relevant conditions and highlight the potential utility of selenium-modified substrates for electroanalysis of chalcogen-containing species.

Electrochemical Study of Selenocystine Reactivity and Reduction at Metallic Surfaces

“…Figure shows a comparison of cyclic voltammograms recorded for increasing selenocystine concentrations (0.2–2 mM) in phosphate buffered saline (PBS, pH 7). For each concentration, the electrode has been reductively cycled (−0.2 to −0.7 V vs. Ag/AgCl) for 100 consecutive scans in the selenium‐containing solution to reach a steady signal . The dependence of peak current on concentration is linear (Figure S1), consistent with the measured redox process corresponding to the reduction and oxidation of bulk selenium analyte.…”

“…The voltammetric response of selenocystine on gold features a quasi‐reversible redox couple centered at −486 mV vs. Ag/AgCl . Figure shows a comparison of cyclic voltammograms recorded for increasing selenocystine concentrations (0.2–2 mM) in phosphate buffered saline (PBS, pH 7).…”

“…Previous work from our laboratory illustrated that the adsorbate layer that results from the reactivity of the diselenide with gold is not redox‐active in our potential window of interest . Here we evaluated alternate conditions under which we could establish a reproducible and stable Se−Au surface modification.…”

“…Building on preliminary results, we further explored the sensitivity of the selenium‐gold adsorbate to the selenium source. Selenium dioxide (SeO 2 ) was employed as the reactive chalcogen‐containing species instead of selenocystine.…”

“…Initial studies from our laboratory demonstrated the utility of gold electrodes for the voltammetric analysis of the selenocysteine (SeCys)/selenocystine (SeC) redox couple at physiological pH . Spontaneous reactivity of selenocystine with gold yields conductive modified electrodes that allow for the observation of diffusional voltammetry of bulk selenium analyte.…”