Apr 5, 2011
Force scanning: quick maps and measurements of living cells
Atomic force microscopy is a popular technique for creating high-resolution images of nanoscale structures and for measuring the mechanical properties of materials with great precision. Combining these two capabilities into one simple, experimental technique provides many opportunities for scientists working in a variety of fields. It is especially useful for researchers studying the relationship between the mechanics and the biological behaviour of living cells and tissues. Having the ability to match mechanical properties to physical features provides a richer understanding of what occurs as cells move and interact with each other and their environment.
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.
About the author
Eric Darling, PhD, is an assistant professor at Brown University in Providence, RI, US. His lab is part of the Center for Biomedical Engineering, which is an interdisciplinary programme between Brown's Division of Biology and Medicine and School of Engineering. The research presented here was supported by faculty start-up funding and research grants through the National Institutes of Health (NIAMS, NCRR). The entirety of this study was conducted by Dr Darling, whose interests focus on the relationship between the mechanical and biological properties of cells and tissues.