Biomedical Engineering Reference
In-Depth Information
7.2.4
Physicochemical Interactions between Bacteria
and Surfaces
Adsorption and attachment are the primary steps for bacterial adhesion
to surfaces [44]. Generally, bacterial cells choose solid surfaces on which
to proliferate instead of surrounding growth liquid medium. Bacteria ini-
tially adhered to the biomaterial surface through physical interactions like
long
−
range interaction (nonspecifi c, distances
>
50 nm) and were further
attached by the short range (distances
5 nm) [45]. After this initial attach-
ment, bacteria makes chemical bonds with the surface proteins [46].
After the physicochemical interactions between bacteria and biomate-
rial surfaces, molecular
<
specifi c reactions become predominant for adhe-
sion. The bacterial adhesion on biomaterial surface becomes stronger by
the selective
−
bridging function of the capsules, fi mbriae and slime [47].
Bacteria has polysaccharide strands that mediate in the attachment to var-
ious biomaterial surfaces [48]. Also, bacteria have different types of sur-
face proteins (for example,
S. aureus
with fi bronectin) [49]. The interaction
between bacteria and biomaterial is illustrated in Figure 7.10.
−
7.2.4.1 Factors Infl uencing Bacterial Adhesion
Bacterial adhesion is an extremely complicated process that is affected by
many factors including the culture environment, surface chemical compo-
sition, surface roughness and bacterial characteristics, etc. These factors
are briefl y explained below.
7.2.4.1.1 Culture Environment
Environmental factors that affect the bacterial adhesions are temperature,
bacterial population in growth medium, duration of culture, antibiot-
ics concentration in growth medium and associated fl ow conditions [9].
Flow conditions highly affect the attached bacterial population as well
as the biofi lm arrangement and performance [50]. Higher shear rates are
Pilli/Protein molecules
on cell surface
Bacterial cells
Adsorbed protein
molecules on
biomaterial surface
Biomaterial surface
Figure 7.10
Illustration of the interaction of bacterial cells on biomaterial
(adapted from ref. [9]).
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