Strategies to Prevent Bacterial Adhesion on Biomaterials - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 183

7.2.6.1 Electric Field

Biofi lm formation and microbial adhesion have been extensively studied
and are generally believed to depend on the factors explained in Section
7.2.4. In a study, it was reported that application of 100 μ A direct current

(DC) showed 78% bacterial detachment, whereas 100 μ A block current

stimulated only 31% of initially − adhered staphylococci to detach from sur-

gical stainless steel [107].
In another study on electric fi eld with block currents of 15, 60 and 100

A
of different frequencies (0.1-2 Hz) and varying duty cycles (5-50%), signifi -
cant bacterial detachment from stainless steel is reported. Figure 7.22 depicts
that 100

μ

A block current show staphylococci detachment of ~ 76 % from stain-
less steel substrate, but the duty cycle 5% was reported insuffi cient to cause
bacterial detachment [106]. However, the direct currents have a disadvan-
tage over alternating current, by generating an excess of ions on the steel that
results in terms of negative osteogenesis and fixation [108]. It is reported that
the applied alternating field direct the hydrated ions to go along the fields as
well as dragging water along with them. As a result of such fluid flow, cells
experience an additional force, that motivate bacterial detachment [109].

μ

7.2.6.2 Magnetic Field

The available literature regarding magnetic effect on bacterial cells pro-
vides the evidence that magnetic fi eld kills bacteria [110]. The effect of mag-
netic fi eld on the bacterial cell depends on the exposure duration as well as
strength of magnetic induction [111]. The effects of magnetic fi elds are not
necessarily to be bacteriostatic, as some studies report that the bacterial

1.20E+07

1.00E+07

8.00E+06

6.00E+06

4.00E+06

2.00E+06

0.00E+00

0 4000 8000 12000 16000 20000 24000

Time (s)

Figure 7.22 Three examples of times series involving adhesion and electric
current induced detachment of S. epidermidis from stainless steel. Here : 2 Hz,

50%, 100

−

μ A; : 0.5 Hz, 50% , 100 μ A; ×: 2 Hz, 5%, 100 μ A [106]. (Copyright (2013),

with permission from Elsevier)