While conventional thinking in cell biology assumes that cells communicate via biochemical signalling, there is an increasing number of examples where mechanical effects are equally important, e.g. in development, physiology and disease. The current gold standard for imaging the mechanical forces applied by living cells are traction force microscopy and elastic micro-pillar arrays. However, these methods require zero-force reference images and thus removal of cells from the substrate, rendering them unavailable for immunostaining. In addition, fluorescence microscopy is usually needed, which can lead to photo-damage. Finally, both these methods have limited sensitivity to vertical forces. These factors have so far prevented the widespread use of cell mechanical assays, e.g. in clinical settings. What is currently missing is a generally applicable method to image cellular forces that is compatible with immunostaining and resolves weak forces with high throughput. Our novel micro-interferometer based force sensors provide direct, robust and non-destructive imaging of forces associated with various types of mechanical cell-substrate interaction.
While existing methods are generally based on localization microscopy, our novel sensors detect cell-induced substrate deformations interferometrically and thus provide unprecedented sensitivity. They are able to resolve not only forces exerted by cells that form firm focal adhesion contacts but can also detect protein-specific cell-substrate interaction and quantify much weaker vertical forces (down to piconewtons), e.g. during amoeboid-type cell migration through confined environments or the protrusion of podosomes. The new method requires no zero-force reference image, which enables continuous, long-term measurements of multiple cells on one substrate as well as further investigation of cells by immunostaining or other assays. As the interferometric sensors are read out by low-intensity wide-field imaging, forces are recorded at each point of the image simultaneously, thus facilitating observation of multiple cells at once without inducing photo-damage.
The University filed UK patent application No GB1421214.6 on 28th November 2014 covering the technology concept and this application is now proceeding through national phase applications in the US 15/531118, Europe 15794269.9 and Singapore Patent Office as 11201704325Q.
St Andrews would welcome enquiries from commercial parties interested in developing applications for this novel interferometer-based sensor technology.