Characterization of the Iron Species Released by Ferritin Immobilized on Self-Assembled Monolayer Modified Gold Electrodes

Abstract

Iron is released following electrochemical reduction of immobilized ferritin. In this work, voltammetry is used to elucidate the identity of the released iron. Ferritin was covalently immobilized on 6-mercaptohexanoic acid modified gold electrodes. The current-potential curve shows an initial cathodic peak indicating the reduction of ferritin. The return scan gives an anodic peak that is probably due to the oxidation of released Fe(H₂O)₆²⁺. The second cycle shows a new cathodic wave suggesting the reduction of the iron species. Voltammetry, while stirring the cell solution, reveals that the released iron is dissolved while the oxidized form is immobilized. The cathodic peak potential of the oxidized iron species has a dependence of 120 mV/pH indicating a two-proton exchange per electron transferred, suggesting that Fe(H₂O)₆²⁺ is oxidized to Fe(OH)₂⁺. Results from voltammetric scans in the presence of hesperitin, Trolox, and maltol further suggest that the oxidized form of iron is Fe(OH)₂⁺.

Keywords:

• Ferritin
• voltammetry
• immobilized iron

Acknowledgements

The authors gratefully acknowledge the Slippery Rock University Faculty-Student Research program for support of this work.