In particular, the group wants to find out more about the cellular mechanisms that lead to an increase in the stiffness of endothelial cells and believes that the electrical potential difference across the plasma membrane might be involved.

Integrated microscopy

To investigate the hypothesis, the team has devised an experimental approach that combines fluorescence-based electrical membrane potential- and atomic force microscope (AFM)-based stiffness measurements. In practise, the set-up is realized by integrating an AFM and an epifluorescence microscope.

Using this technique, the researchers can simultaneously measure the dynamics of the membrane potential and the mechanical stiffness in a living endothelial cell. The cellular stiffness is determined by nano-indentation using an AFM while the electrical membrane potential is measured with bis-oxonol, a voltage-reporting fluorescent dye.

The study reveals that fast (in the range of seconds) membrane potential and stiffness changes are not related to each other, whereas sustained (in the range of minutes) changes in the two parameters do correlate. This suggests a more indirect coupling mechanism between electrical and stiffness changes in endothelial cells.

The method allows the scientists to study any kind of dynamic fluorescence (for example, Ca2+, pH, Na+, NO or fluorophore-linked proteins) together with mechanical properties of living cells. Now it is possible to start finding answers to a wide range of questions such as the linkage between cell mechanics and cell function.

The researchers presented their work in Nanotechnology.