A beginner's guide to atomic force microscopy probing for cell mechanics

Abstract

Atomic Force microscopy (AFM) is becoming a prevalent tool in cell biology and biomedical studies, especially those focusing on the mechanical properties of cells and tissues. The newest generation of bio‐AFMs combine ease of use and seamless integration with live‐cell epifluorescence or more advanced optical microscopies. As a unique feature with respect to other bionanotools, AFM provides nanometer‐resolution maps for cell topography, stiffness, viscoelasticity, and adhesion, often overlaid with matching optical images of the probed cells. This review is intended for those about to embark in the use of bio‐AFMs, and aims to assist them in designing an experiment to measure the mechanical properties of adherent cells. In addition to describing the main steps in a typical cell mechanics protocol and explaining how data is analysed, this review will also discuss some of the relevant contact mechanics models available and how they have been used to characterize specific features of cellular and biological samples. Microsc. Res. Tech. 80:75–84, 2017. © 2016 Wiley Periodicals, Inc.

Atomic Force Microscopy in Characterizing Cell Mechanics for Biomedical Applications: A Review

“…1C. Cellular Young's modulus can be obtained from both approach curve and retract curve depending on the theoretical models applied [27], while the retract curve can also be used for analyzing the adhesion forces [34].…”

“…The spring constant of AFM cantilever should be calibrated during the experiments. For calibration, force curves are recorded on a stiff (unindentable) substrate to calibrate the deflection sensitivity of the cantilever and then the spring constant of the cantilever can be calibrated by thermal noise method [27]. It should be noted that the spring constant of AFM cantilever should be comparable with the stiffness of the cell being measured, thus often the AFM cantilevers with the spring constant in the range 0.01-0.5 N/m [46] are used in measuring cell mechanics.…”

“…With AFM, the individual microvilli on living mammalian cell surface can be visualized [24], nanoscale organizations on living bacterial cell surface can be revealed at single-molecule level [25], and the dynamic activities of single molecules at work on cell surface can be filmed by highspeed AFM [26]. Beyond topography imaging, AFM also provides high-resolution maps of cellular mechanical properties, thus acting as a reliable tool for correlating mechanics with the structures and functions of the sub-cellular structures (e.g., cytoskeleton and organelles [27]). The applications of AFM in detecting cell mechanics in the past decades have yielded significant breakthroughs in cell behaviors, contributing much to the field of cell biology and medicine.…”

Peculiarities of living cell response to the external stimuli revealed via quasistatic mode of atomic force microscopy

“…This imaging method allows studying cell morphology and mechanical properties with submicrometer resolution and under physiologically relevant conditions. Various cellular processes are associated with mechanical properties of cells: shape maintenance, migration, differentiation, and division [3]. Several pathologies are known to change the cell mechanical phenotype [4].…”

“…The measurement of the Young's modulus of a single cell is based on the AFM nanoindentation technique. It implies that the AFM probe compresses the sample with a preset force, and the induced cell deformation is employed to calculate the Young's modulus according to the selected contact mechanics model [3].AFM Force Spectroscopy and Force Volume are the most widespread modes for living cell Young's modulus measurements. These modes are slow in operation and have low data flow rate.…”