Biomedical Engineering Reference
In-Depth Information
Figure 7.1
Uses of cellular engineering.
various parameters that define the cellular environment are manipulated and mod-
eled is discussed.
7.2 Cellular Interactions
7.2.1 Cell Culture Microenvironment
A cell culture environment is designed to mimic human homeostasis that is critical
for survival, growth, and the possible expression of the specific function of cells.
A basic culture medium can be formulated to control the pH, temperature, and
osmolarity within a narrow range of physiologically acceptable conditions. Since
cells need nutrients for energy and metabolism, the medium also provides carbon
and nitrogen sources. In addition, several small molecules and critical vitamins that
are essential for cell viability are incorporated into the medium. Depending on the
tissue of origin, each type of cell will have different requirements for culture. Cells
will respond in different ways to signals from their environment. Hence, more so-
phisticated microenvironments can be obtained by altering four major components
(Table 7.1) in addition to this basic medium.
Polystyrene is the most commonly used substrate for cell culture as it is easy
to mold into a required shape, relatively inexpensive, and transparent (or opti-
cally clear). Furthermore, the hydrophobic (nonwettable) surface of polystyrene to
which cells have difficulty attaching can be easily modified by a variety of chemical
(e.g., sulfuric acid) and physical (e.g., corona discharge, gas-plasma or irradiation)
methods. Commercial tissue culture plasticware is made of polystyrene that has
been exposed to an ionized gas generated by an electric arc. The ionized gas reacts
with the polystyrene surface and changes the uncharged hydrophobic surface into
a more ionic hydrophilic surface. When serum is added to a culture medium, some
of the serum proteins adsorb to the surface of the treated plastic and cells readily
attach to these adsorbed proteins. In particular, fibronectin and vitronectin found
in the serum are important for cell attachment. When using a serum-free medium,
the plastic tissue culture dishes are sometimes coated with ECM molecules (e.g.,
