Angewandte Chemie International Edition

Cover image for Vol. 56 Issue 35

Editor: Peter Gölitz, Deputy Editors: Neville Compton, Haymo Ross

Online ISSN: 1521-3773

Associated Title(s): Angewandte Chemie, Chemistry - A European Journal, Chemistry – An Asian Journal, ChemistryOpen, ChemPhotoChem, ChemPlusChem, Zeitschrift für Chemie

For full article and contact information, see Angew. Chem. Int. Ed. 2001, 40 (5), 139-143

No. 05/2001

Feeling up Cells

Locally resolved detection
of cell signals with microelectrodes

No matter how small, a living cell does not have a uniform structure. Instead, it has "organs", called organelles, which are assigned various tasks. Even the "shell" of the cell, its membrane, is not uniform. Functional building blocks, such as ion channels, can be distributed unevenly over the membrane. To be able to observe the physiological activities of an individual living cell at specific locations is the challenge researchers in Bochum have set themselves.

With the help of microelectrodes it has already been possible to examine a number of biological phenomena, such as the distribution of ion channels or the shuttling of messenger substances, in individual cells. In order to do this, the microelectrode must be brought very close to the cell – either manually or with piezo-driven micromanipulators. The electrode is moved toward the cell until it touches the membrane and is then pulled back to an exact distance. This is not a satisfactory method, as the electrode can get contaminated, the cellular processes can be disrupted or the cell can be destroyed. Also, the reproducibility leaves a lot to be desired.

Wolfgang Schuhmann and his team have developed a highly promising alternative. They use a scanning electrochemical microscope equipped with a specially manufactured superfine carbon fiber electrode. The crucial thing is that the electrode is made to vibrate: as the distance between the electrode and the cell surface decreases, shear forces dampen the vibrations. The changes in the vibrations can be measured with the help of a laser. This allows the researchers to keep the distance from the cell – about 0.0001 mm – controlled and constant.

When the researchers scan the cell surface with their novel apparatus while recording the deflection of the electrode, they obtain a topological picture of the living cell – without disturbing it. The electrode can thus be placed in a precise location on the cell. Active agents can then be introduced through a glass capillary, and the cell’s reaction, such as the release of neurotransmitters, can be monitored with the electrode. After a rest phase the measurement can be repeated at another location on the cell.

"Our next goal is to further decrease the diameter of the electrode, because this limits the local resolution," says Schuhmann. "We also hope to use this to learn about metabolic reactions in cell substructures."