Since its development in the eighties, atomic force microscopy (AFM) has proved itself to be the perfect tool to image a wide range of samples and characterize their mechanical properties with an unprecedented accuracy. Force spectroscopy emerged in the nineties as an ideal technique to extract the sample’s stiffness or elasticity, and, to date, is the most commonly used AFM technique in biology. But over the last decade, other quantitative modes have offered benefits in terms of resolution and information. Recently an oscillating technique called PeakForce Tapping (PFT) has been released. Whereas the cantilever is oscillated far below its resonance frequency (typically 1 kHz), a force/distance curve is recorded each time the tip contacts with the surface. From each of those force curves, mechanical information can be extracted in real time. If the tip is calibrated prior to the experiment, all information is displayed in a quantitative manner. This technique has proven suitable for a wide variety of samples ranging from stiff biopolymers to live cells.
In this presentation, we will be focusing on a few examples where PFT has been successfully used on biological samples in near-physiological conditions to address issues of medical or pathological order. More in particular, via the use of PFT, we’ll be reviewing how AFM can be considered as a nanotool to distinguish cancer cells from their normal counterparts by extracting the cell’s mechanical properties or measuring their migration speed; or to investigate the effects of diabetes or atherosclerosis on tissue sections with a submicrometer resolution. The interest of the technique also lies in the possibility to combine it in real time to other more traditional microscopy techniques, thus providing complementary information.