Biomedical Engineering Reference
In-Depth Information
adhered bacteria, but it was verified that the removed bacteria could again accu-
mulate on the surface and thus the problem of surface contamination continues.
Besides, according to Wagnera et al. (
2004
), when an anodic current or potential is
applied, the inactivated bacteria tend to remain on the surface providing new sites
for bacterial adhesion. Thus, the control of bacterial adhesion through the exclusive
application of anodic current is still limited. In order to try to overcome these
limitations, Hong and colleagues (
2008
) investigated the specific role of electric
currents in bacterial detachment and inactivation when a constant current was
applied in the cathodic, anodic, and block modes. These authors observed that the
application of cathodic current promoted the detachment of adhered bacteria by
electrorepulsive forces, but bacteria remaining on the surface were still viable.
On the other hand, the anodic current inactivates most of the remaining bacteria.
Thus, these authors concluded that the best electrical strategy for reducing bacterial
adhesion consists of the application of a block current.
Flint and coauthors (
2000
) observed that it may be possible to disrupt the
attachment of thermo-resistant streptococci to stainless steel by applying a small
voltage. In fact, when a voltage of 9 V and a current of 40 mA were applied to a
suspension of
S. thermophilus
held between stainless steel electrodes, attachment to
the cathode was reduced, whereas attachment to the anode was inhibited. This may
result from the disruption of the electrical bilayer on the substrate.
An approach using electrical current to enhance the activity of antimicrobials
against established biofilms has also been proposed. Blenkinsopp et al. (
1992
)
found that three common industrial biocides (glutaraldehyde, a quaternary ammo-
nium compound and kathon) exhibited enhanced action when applied against
P. aeruginosa
biofilms within a low strength electric field with a low current
density.
Concerning its mode of action, it has been suggested that the mechanism of
antibacterial activity of electrical current results from the oxidation of enzymes and
coenzymes, membrane damage leading to the leakage of essential cytoplasmic
constituents, and toxic substances (e.g., H
2
O
2
, oxidizing radicals, and chlorine
molecules) produced as a result of electrolysis and/or a decreased bacterial respi-
ratory rate (del Pozo et al.
2009
).
5.3 Electrolyzed Water
Electrolyzed water (EW) has been used in the food industry as a novel disinfecting
agent. This process was shown to be more efficient than water and chlorine
solutions as a sanitizer of meats, some fresh products, cutting boards, and utensils.
EW is generated in a cell containing inert positively charged and negatively
charged electrodes separated by a septum (membrane or diaphragm) (Al-Haq
et al.
2005
). By electrolysis, a dilute sodium chloride solution dissociates into
acidic electrolysed water (AEW; pH between 2 and 3, oxidation-reduction poten-
tial of N1100 mV, and an active chlorine content of 10-90 mg/L), and basic
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