Bacterial Adhesion and Interaction with Biomaterial Surfaces - Biointerfaces: Where Material Meets Biology - page 380

shown in Figure 13.6. The total accessible top pillar surface area for bacteria
interaction is only about 24.5% of a smooth surface. The diameter and
separation of pillars are smaller than the dimension of bacterial cells, en-
suring a reduction in available contact area and minimizing the opportun-
ities for bacteria to become lodged in the spaces between pillars.
The surface texturing greatly increases the overall surface roughness
(RMS, R q ) and surface hydrophobicity. For example, pattern 500/500 nm has
the roughness of 248.5 3.4 nm and water contact angle of 138.0 3.11,
while the smooth polyurethane surface is with roughness of 15.7 2.7 nm
and water contact angle of 92.8 3.01. The increase in hydrophobicity of the
textured surfaces is believed to be due to air captured in the spaces between
pillars, which may prevent the intimate contact of the surface with bacteria
resulting in low adhesion.

d n 3 r 4 n g | 3

13.4.3 Bacterial Adhesion and Biofilm Formation on
Textured Surfaces
Bacterial adhesion to smooth and textured polyurethane films was assessed
across a low shear stress range (0-13.2 dyn cm 2 ) in phosphate buffered
saline (PBS) solutions with or without plasma proteins. A rotating disk sys-
tem (RDS) 152 was used to produce well-defined dynamic flow conditions
across the polyurethane surface. Figure 13.7 illustrates the adhesion of
bacterial strains S. epidermidis RP62A and S. aureus Newman on smooth
control and textured polyurethane surface with 500/500 pattern.
A significant reduction in bacterial adhesion was observed at nearly all shear
stresses for a textured surface for both strains in PBS solution for 1 h. The
500/500 pattern produced a reduction in adhesion of S. epidermidis RP62A
ranging from 68.1% to 89.2% with an average reduction of 81.4 7.7% over
the shear stress range of 0-13.2 dyn cm 2 (Figure 13.7a). S. aureus Newman
showed lower adhesion to smooth polyurethane films than did S. epidermidis
RP62A, with reductions in adhesion on the 500/500 pattern polyurethane
surface being 82.7% at the near static condition (

.

0.2 dyn cm 2 ), and de-
creasing to approximately 48% with increasing shear (Figure 13.7c).
The presence of proteins influences the adhesion of bacteria on bio-
material surfaces. A greater decrease in adhesion was observed on all poly-
urethane surfaces when platelet poor plasma proteins (PPPs) were added in
PBS solution. The decrease in adhesion is believed to be due to the presence
of a large amount of serum albumin in PPPs. The adsorption of albumin
suppressed the adhesion and interaction with biomaterial surface. 37 How-
ever, bacterial adhesion still significantly decreased on the textured surface
for both strains, the reduction rates in adhesion range from 44.8% to 81.5%
for S. epidermidis and from 57.1% to 84.1% for S. aureus over the whole shear
stress range. It should be noted that adhesion of S. aureus was run in 25%
human serum (clotting factors removed from plasma) instead of plasma due
to the clumping by coagulase positive S. aureus in 25% normal plasma.

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