| Abstract: |
Based on its standard reduction potential, oxidized ferrocenemethanol (FcCH2OH+) may act as an alternate electron acceptor to oxygen during cellular metabolism. By locally oxidizing ferrocenemethanol (FcCH2OH) at a microelectrode, we probed the metabolic activity of individual HeLa cells using a scanning electrochemical microscope. For some cells, FcCH2OH+ penetrated the cell membrane and was reduced, leading to an enhanced current known as positive feedback. For other cells, FcCH2OH diffusion was blocked by the cell membrane, leading to a lower current known as negative feedback. Cells exhibiting both positive and negative feedback fluoresced green (live) upon exposure to calcein am, which indicates esterase activity in living cells. These measurements therefore appear to distinguish live, metabolically active cells from live, metabolically inactive cells. Since cells with uncompromised membranes may retain esterase activity and an early stage of apoptosis is cessation of metabolic activity, electrochemical metabolic activity measurements may be an early indicator of programmed cell death. |
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