Bacterial Adhesion and Interaction with Biomaterial Surfaces - Biointerfaces: Where Material Meets Biology - page 384

length for the establishment of the desired hydrodynamic conditions. 165 The
fluid dynamics in flow chambers have been characterized elsewhere. 160
Another configuration of chambers is that of the radial flow chamber. It
consists of two flat disks separated by a thin gap, and the fluid flows in
through the center of the fixed disc and flows out radially through the gap
between the discs. Such a flow pattern provides a gradient of shear stress
becoming progressively lower at the outer edge of the disc. The fluid dy-
namics can be found elsewhere. 166
RDS can be used to produce well-defined dynamic flow conditions
across the material surface. The details of the system have been described
elsewhere. 34,152 When operated under laminar flow conditions, the wall
shear stress at the surface of the RDS varies linearly with the radial distance
from zero at the center point, while the flux of particles (bacteria) is
uniform over the entire surface. By assessing adhesion of bacteria at dif-
ferent area, it is possible to determine the variation in adhesion with wall
shear stress.
Figure 13.10 illustrates the schematic diagram of RDS, a technique we and
others used extensively. 129,152,153,164,167 Biomaterial samples are mounted on
to a stainless steel disk. For convenience, the stainless steel disk to which the
biomaterial sample is mounted can be scribed with concentric circles at
1 mm radial increments and with radii at 601 increments. The disk is at-
tached to the shaft of an RDS via a stainless steel threaded piece. The shear
stress rates across the sample vary from 0 dyn cm 2 at the center to the
maximum value at largest radial distance (Figure 13.10c). The shear stress
range can be adjusted by the control of rotating speed. The fluid dynamics
on surface of RDS was described elsewhere. 129

d n 3 r 4 n g | 3

.

(a) (b) (c)

Rotating shaft

Steel mounting
stub

Biomaterial
sample
Bacterial
suspension

Distance to center

Figure 13.10 Schematic diagram of (a) rotating disk system, (b) the scribed mark-

ings metal mounting stub indicating areas for epifluorescence micro-
scopy analysis of bacterial adhesion and (c) shear stresses linearly
increased with the distance to center.
Adapted from Milner et al. 152 with permission from John Wiley and
Sons.