Biology Reference
In-Depth Information
The rheological and mechanical properties of cells have been measured
and directly linked to their function, metastatic potential and cytoskeletal
architecture.
49-53
With the development of the AFM it quickly became possible to apply
known and controlled forces to very localized positions on living cells as
well as measure their mechanical properties in physiological conditions.
The AFM is an effective tool for investigating mechanical and material
properties of biological samples in their native conditions. These include
the investigation of cellular strain distribution and cytoskeleton disruption
in response to stress,
During
such experiments, living cells can be kept at physiological conditions by
heating of the stage on which the culture dish is mounted or having the
whole microscope apparatus inside a controlled incubator. pH levels can be
monitored and adjusted during the experiment using buffered culture media.
Recent technical developments have integrated traditional microscopy
methods, such as luorescence and laser scanning confocal microscopes
with AFM systems. This has enabled the simultaneous measurement of
material properties of living cells and their biological responses.
54
and the extraction of Young's modulus.
55-58
The
combined AFM-luorescence microscope apparatus can also be used to
apply controlled mechanical perturbations on the living cell, while imaging
the real-time deformations and/or displacements that occur intracellularily.
The AFM has found an extremely large number of very different
applications in biology. Not only is the AFM capable of delivering and
measuring small forces and mechanical dynamics, it is also an extremely
powerful imaging tool. Now capable of sub-nanometre resolution imaging at
high speeds (>30 fps) the AFM has found many uses in studying molecular
structures in physiological environments with high temporal and spatial
resolution. Moreover, the AFM is also highly sensitive to small forces and
capable of delivering forces over several orders of magnitude (pN-nN). The
AFM has been employed to detect local nanomechanical dynamics of living
mammalian and bacterial cells undergoing important physiological processes,
as well as detecting the onset and progression of disease states.
54,59-61
The shear
number of imaging and force spectroscopy applications in artiicial bilayers,
mammalian cells, bacteria, multicellular complexes, tissues is beyond the
scope of this particular chapter but have been reviewed previously.
17,64,65
Therefore, here, we limit our discussion to living mammalian cells and
applications that utilize the AFM. Speciically, we will discuss the AFM as a
tool to deliver temporally and spatially controlled localized nanomechanical
forces to living mammalian cells while simultaneous optical measurements
are performed to image biological responses at the single cell level.
The popularization of luorescent tags, particularly through transfection
or commercial dyes, became useful for direct visualization of the effect of
applied force on the inner structure of the cell. Previous work combined
62,63
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