Bacterial Adhesion and Interaction with Biomaterial Surfaces - Biointerfaces: Where Material Meets Biology - page 371

13.3 Factors Influencing Bacterial Adhesion and
Interaction with Biomaterial Surfaces
Bacterial adhesion is the critical step in the pathogenesis of biomaterial
associated infection. Factors that influence bacterial adhesion on a bio-
material surface include the nature of environment, type of microorganism,
and properties of material, and each one of these factors is in turn affected
by several other parameters. 18

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13.3.1 Biomaterial Surface Properties Affect Bacterial
Adhesion
Biomaterial surface characteristics including surface chemistry, roughness,
surface energy, and charge are known to be the major factors to determine
initial bacterial adhesion and biofilm formation on implant surfaces. 94-96
Surface material composition determines physico- and chemical properties,
and moderates the bacterial adhesion. On a series of gold film surfaces with
self-assembled monolayers (SAMs) formed, adhesion of S. aureus was found
to be lowest on the ethylene oxide-bearing surfaces, followed by the hydroxyl
surfaces, while adhesion on the carboxylic- and methyl-terminated SAMs was
much higher. 35 The Anderson group studied the adhesion of S. epidermidis
on polymeric biomaterials with different charged surfaces and hydro-
phobicity, and found surface chemistry significantly impact the initial ad-
hesion and aggregation of bacteria on biomaterials. 97 Modification of
polyurethane with polyethylene oxide significantly inhibited S. epidermidis
biofilm formation over 48 h in vitro. 37
Binding of bacteria to surfaces is influenced by the properties of all three
phases involved (substrate, bacteria, and medium). From the thermo-
dynamic theory for the adhesion of small particles from a suspension onto a
solid substratum, it is predicated that bacterial cells preferentially attach to
hydrophilic substrata of relatively high surface energy, when the surface
energy of the bacteria is larger than that of the medium in which they are
suspended. When the surface energy of the suspending medium is greater
than that of the bacteria the opposite pattern of behavior prevails. 98 How-
ever, the application of thermodynamic theory has not been entirely suc-
cessful in explaining or predicting all various attachment behaviors in
bacterial system. 30 An adhesion study of S. epidermidis to plasma modified
polyethylene terephthalate films demonstrated that the increase in the free
energy of polyethylene surfaces by He and He/O 2 plasma treatments sig-
nificantly reduced the adhesion of S. epidermidis under static condition. 99
Similar experiments were carried out on the model glass surfaces coated
with SAMs. Bacterial adhesion was found to depend on the monolayer's
terminal functionality. Adhesion was higher on the CH 3 followed by the
positively charged NH 2 , the non-charged NH 2 groups, the COOH, and min-
imal on the OH-terminated glass, in accordance with the predictions of the

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