Features of single force

One force-distance curve, recorded upon touch of two cells, is a real goldmine. Here the gold is hidden in characteristic featurs of the curve, revealing important parameters of the established 'contact'. The most interesting and valuable parameters are the maximal downward deflection of the cantilever, which is represented by the 'Adhesion Force', and the separation energy which is the green area on the diagram below.

Characteristic features of a force-distance curve

Both the adhesion force and separation energy are characteristics of the binding strength between the two interacting cells. The 'indentation ~ elasticity' might be important too, but it is hard to distinguish the contribution of the participating cells. However, it can be regarded as characteristic of the total 'two cell system'.

Measuring single cell interactions

          Well, this is a quite large field, so I do not intend to cover all. Basically, life is based on cellular interactions. Of course everything is mediated by molecules, but single cell interactions are not so easy to follow, and investigate. This holds for mechanical investigations as well. As single living cells size ranges few tens of micrometers (half to tenth of human hair diameter), atomic force microscope based single cell force spectroscopy is a suitable method to manipulate and measure single cell interactions. 

          All we need to do, is to immobilize one cell at the end of a (not necessarily) tipless atomic force microscope cantilever, and another to an arbitrary surface. Pushing this cell-decorated cantilever against the cell covered surface so called force-distance curves can be recorded. 

This setup is an easy and quick way to investigate mechanical aspects of single cell interactions. Here is a short illustration, how the measurement happens. The recorded curve has many important parameters concerning elastic and adhesive properties of the studied cells. Few of these will come in next post.