Researchers in the Center for Biomedical Engineering at Brown University, US, have developed a novel, AFM-based approach to quickly capture spatially defined, mechanical properties of soft, biological materials. The technique requires no special hardware or complex mathematics to obtain reproducible stiffness values for living cells, biological tissues or any other deformable materials. To achieve these results, a series of contact-mode scans at different setpoint forces is first collected.

Contact mode is a technique in which the AFM probe is physically touching the sample throughout the scan. By incrementally increasing the setpoint force, more deformation into the sample occurs. The resulting topographical images are virtually "stacked" to create a matrix of force-indentation curves that can be processed to obtain quantitative stiffness values. These mechanical properties are then mapped to precise locations on the sample, highlighting areas of high and low stiffness. Validation of the technique is demonstrated for several different samples, including soft biomaterials (agarose), living cells (individual and cell–cell interfaces) and whole tissues (cartilage).

Suits most AFMs

The force scanning technique holds great promise for investigating biological samples because it can capture high-resolution stiffness maps quickly in physiological environments. Analyses reported in the manuscript demonstrated that force scanning can gather in a matter of minutes the same quality and quantity of data that would take years using currently employed AFM measurement techniques. It can be implemented on any AFM system that can capture contact-mode images, allowing the technique to be accessible to most investigators.

The team is using the method to study adult stem cell differentiation by monitoring the nanoscale changes in cell morphology, behaviour and mechanical properties.

More information can be found in the journal Nanotechnology.