Accurately measuring respiratory activity of single living cells by scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) is a powerful tool to examine the respiratory activity of living cells. However, in SECM measurements of cell respiratory activity, the signal recorded usually also includes the signal corresponding to the cell topography. Therefore, measurements of cell respiratory activity using conventional SECM techniques are not accurate. In the present work, we develop a method for accurate measurement of the respiratory activity of single living cells using SECM. First, cells are immobilized on a glass substrate modified with Collagen. Then, a Pt ultramicroelectrode tip of SECM held at -0.50 V is scanned along the central line across a living cell and a SECM scan curve, i.e., the relationship of the tip current versus the displacement (the first scan curve) is recorded with a negative peak. The peak current i(p) an this first scan curve is composed of i(p1), which corresponds to the cell respiratory activity and i(p2), which corresponds to the cell topography. In order to isolate the i(p2) component, the cell is killed by exposing it to 10 x 10(-3) mol/LKCN for 10 min. The tip is then scanned again with the same trace over the dead cell, and a second SECM scan curve is recorded. Noting that the topography of the dead cell is the same as that of the living cell, this second scan Curve with a negative peak corresponds now only to the Cell topography. Thus, i(p2) is obtained from the second SECM scan Curve. Finally, i(p), corresponding to the respiratory activity of the living cell can he accurately calculated using i(p1) = i(p) - i(p2). This method can be used to monitor real-time change in the respirator activity of single cells after exposing them to KBr, NaN3 and KCN. (C) 2008 Elsevier B.V. All rights reserved.