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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