Biomedical Engineering Reference
In-Depth Information
population increases during exposure of the growing culture to the mag-
netic fi elds [112]. However, a majority of the experiments till now show
a negative effect of magnetic fi eld on bacteria, and the effects were more
pronounced with increasing strength of magnetic fi elds, time of exposure
and temperature [113]. As far as the frequency is concerned, inhomoge-
neous fi elds were found to be more effective in reducing the cell number
than the homogeneous ones [114]. In addition, it has also been shown that
the intermediate frequency magnetic fi eld has no effect on the morphology
of the bacteria, irrespective of the exposure time [115]. Further, it has also
been shown that extremely low frequency and low magnitude magnetic
fi elds have no effect on the viability of bacteria [116]. When the magni-
tude of fi eld strength is considerably increased, the static magnetic fi elds
have been shown to cause cell surface damage [113]. But even ultra
strong
magnetic fi elds, applied after different types of costressing factors, were
not able to cause inactivation in bacteria [117].
On the other hand, very
low strength magnetic fi elds have been shown to have no effect on viabil-
ity of the bacteria. Moderate intensity static magnetic fi eld of 100 mT was
found to inhibit the adhesion of
E. coli
bacteria and
S. epidermidis
bacteria
on control as well as sintered HA substrate as the magnetic fi eld exposure
duration is increased from 30 min to 120 min (Figure 7.23) [110].
Table 7.2 provides a summary of experiments and results of several
magnetic fi eld experiments to assess the effi ciency in causing antibac-
terial property along with explanations. The antibacterial effi ciency is
−
(
a
)
(
b
)
Control (0 min)
HA surface (0 min)
(
c
)
(
d
)
Control (60 min)
HA surface (120 min)
Figure 7.23
Magnetic fi eld exposed
E.coli
bacteria on (a) Control (MF exposure
duration = 0 min), (b) Control (MF exposure duration = 60 min), (c) HA (MF
exposure duration = 0 min), and (d) HA, MF exposure duration = 0 min.
(bar = 10
m, magnetic fi eld strength =100 mT) [110]. (With permission from John
Wiley and Sons)
μ
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