Research Into Expanding the use of AFM for Cell Biological Applications

Dr Clemens Franz leads a group of researchers at the DFG-Centre for Functional Nanostructures at Karlsruhe Institute of Technology where he works on expanding the use of AFM for cell biological applications. Given that AFM cantilevers are ultrasoft springs, they can be used to measure inter- and even intramolecular bonds. To study cell adhesion, Dr Franz and his team often employ AFM-based single-cell force spectroscopy (SCFS). Here, a living cell is attached to the AFM cantilever and brought into contact with a substrate under defined contact conditions. With a force sensitivity spanning over four orders of magnitude, SCFS provides a unique opportunity to measure cellular adhesion forces from the single-molecule level to overall adhesion in the same experimental setup. AFM-based SCFS has provided important insight into molecular mechanisms involved in adhesion force generation, such as the transition from single-receptor mediated to cooperative receptor binding during the initial phase of cellular contact with an extracellular substrate. Furthermore, the adhesive properties of different surfaces can be accurately characterised.

Their latest challenge is to combine AFM with advanced light microscopy techniques, such as laser scanning confocal or total internal reflection (TIRF) microscopy. In this way, the clustering of receptors can be followed in living cells by optical time-lapse-microscopy and directly correlated to the adhesion force information. The group now has built a functional TIRF/AFM setup. The motivation for this work is to better understand fundamental mechanisms of cell adhesion, particularly initial adhesion events when cells first encounter components of the extracellular matrix (ECM). Through the use of micro- or nano-patterned artificial cell adhesion substrates, the goal is to emulate the natural cell environment and to manipulate cell adhesion.