Digital Optical and Scanning Probe Microscopy for Inspection and Manipulation of Biocells - Bioanalysis Advanced Materials Methods and Devices - page 86

7.1 Introduction

Nanobiotechnology and scanning probe microscopy (SPM) are new fields that are
of considerable interest to modern medical science. Currently Atomic Force
Microscopy (AFM) is widely used in medical and biological research using all
varieties of Scanning Probe Microscopy (SPM) [ 1 ]. Even without special methods
of preparation AFM gives an opportunity to investigate the morphology of the
surface of different biological objects with nanoresolution. Also this method allows
the analysis of the physical and mechanical properties at micro- and nanoscales. It
is one of the instruments that enable spatial images of the surface to be realized with
a resolution close to a single atom. AFM has several advantages over optical and
scanning electron microscopes. First of all, it allows the receipt of a three-
dimensional relief of the sample. And by using AFM a conducting surface is not
necessary. Furthermore, the measurements can be made not only in vacuo but also
in an atmosphere of air or any other gas, and moreover, even in liquid. For this
reason AFM gives wide possibilities for the investigation of organic molecules and
living cells [ 2 ]. As shown by Burnham and Colton [ 3 ], Ueda et al. [ 4 ], Ikai and
Afrin [ 5 ], AFM is currently successfully being used to estimate the local elastic and
adhesive properties of the surface.
Additional information about cellular activity in living tissues may be obtained
by DLS laser probing. Laser monitoring of living tissue has been widely discussed
since the inception of lasers [ 6 ]. Coherent light scattered from any diffuse object
produces a random granular interference structure some distance away from the
object. This structure is called a speckle pattern. Such a pattern can also be observed
when a living semi-transparent tissue is illuminated by a laser light. The visible
laser light penetrates into the human skin to a depth of about 200-1,000 m and is

multiply scattered by the erythrocytes flowing inside the smallest candelabra
capillaries as well as by surrounding tissue. So, an image of the tissue illuminated
with laser light differs from an image taken under white light conditions by the speckle
pattern that is superimposed on the surface features of the tissue. As the scatterers
(erythrocytes) move, the speckles also move and change their shape. The dynamic
(time-dependent) biospeckle pattern is formed as a superposition of some moving
speckles with different dynamics, including static speckles. These biospeckles play
a dual role: as a source of noise in tissue images and as a carrier of useful
information about biological or physiological activity of living tissues. The latter
include subskin blood flow and general tissue-structure motility, see, e.g., Fercher
and Briers [ 7 ], Asakura and Takai [ 8 ], Briers [ 9 , 10 ], Okamoto [ 11 ], Aizu and
Asakura [ 12 ].
Modern DLS technique based on computer-aided acquisition and evaluation of
dynamic biospeckle patterns extends the methods of cell monitoring, and it allows
the derivation of a two-dimensional map of subskin erythrocyte motility in living
tissues via statistical analysis of the recorded speckle pattern [ 13 - 16 ].

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