Bacterial Adhesion and Interaction with Biomaterial Surfaces - Biointerfaces: Where Material Meets Biology - page 372

thermodynamic theory. 100,101 However, both studies showed that the in-
crease in the shear rate restricted the predictability of the theory, suggesting
the importance of nature of environment on bacterial adhesion. 99,100
Surface roughness is a two-dimensional parameter of a material surface
and is generally characterized as the value of arithmetical mean deviation
of the height profile (R a ). It has been reported that increases in surface
roughness promotes the bacterial adhesion. 102,103 The reason for this
phenomenon may include that a rough surface has a greater surface area
and provides more favorable site for colonization. However, the effect of
surface roughness on adhesion is apparently related to the degree of
roughness and topographic features of surface. Bollen et al. suggested a
'threshold R a ' that a reduction in surface roughness on titanium surface
below R a ¼ 0.2 mm had no effect on microbial adhesion or coloniza-
tion. 104,105 Tang et al. reported that surface roughness significantly affects
the adhesion of S. epidermidis on silicon surfaces only when the root-mean-
square roughness was higher than 200 nm. 106 The studies of influence of
physical structuring of surface nanofeatures on bacterial adhesion further
revealed the role of surface roughness in bacterial adhesion. Whitehead
et al. 107 measured the bacterial adhesion on Si wafers coated with titanium
having featured surface pit sizes of 0.2, 0.5, 1, 2 mmindiameteranddif-
ferent depths, resulting in R a values ranging from 45 to 220 nm. Results
confirmed that adhesion generally increased with surface roughness,
however, surfaces with 500 nm diameter pits showed the lowest number of
bacterial adhesion. This is probably because the 500 nm pits had a low
contact area and reduced the opportunity for bacteria interaction. Re-
ductioninbacterialadhesionbysurface topography will be further dis-
cussed in the Section 13.4.

d n 3 r 4 n g | 3

.

13.3.2 Effect of Plasma Proteins on Bacterial Adhesion on
Biomaterial Surface
When a foreign material is implanted in the body, plasma proteins rapidly
interact with the surface and form a protein layer. The nature of adsorbed
proteins is affected by the physicochemical properties of surface such as
surface chemistry and charge, roughness, and hydrophobicity, and those in
turn moderate the initial bacterial adhesion.
Through specific interaction between the cell surface receptors and ad-
sorbed proteins ligands, staphylococci have the ability to bind many proteins
found in the blood including Fg, 35 Fn, 108 collagen, vitronectin, 109,110 and von
Willebrand factor. 111 The specific adhesion to these ligands is mediated by
the bacterial cell wall receptors known as MSCRAMM (see Section 13.2.1).
Fg is the most third abundant protein plasma in blood and plays a
prominent role in development of surface-induced thrombosis. It serves as a
ligand binding to the platelet integrin receptor a IIb b 3 , leading to platelet
immobilization, activation, and aggregation. 112,113

It is also found to