Control of Polymicrobial Biofilms: Recent Trends - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 333

technology seems to be in dental fields, as there are concerns that the use of current
antimicrobial formulations can select for bacterial resistance (Roberts and Mullany
2010 ). This is a very logical application given the tendencies of biofilms to rapidly
form in the oral cavity (Diaz et al. 2006 ; Teles et al. 2012 ) and, from a technical
standpoint, the ease of applying photosensitizers and subsequent light treatment to
the affected area. While the clinical data appear to be rather limited at this point,
there have been studies illustrating inactivation of dental plaque biofilm species and
various pathogens that are known to cause periodontal disease and dental caries
(Burns et al. 1995 ; Rovaldi et al. 2000 ). Wilson made the connection that the ability
to kill S. mutans using this technology may result in major innovations for both the
prevention and treatment of dental caries (Wilson 2004 ). The promise of photody-
namic therapy is immense and while it is still being successfully used in some
clinical applications, its potential in the killing of surface biofilms from the human
body is alluring.
4.2 Nonthermal Plasma Technology
One of the more exciting technologies that have recently garnered traction is that of
low-temperature or nonthermal plasma, also known as “cool plasma.” Plasma is a
unique state of matter that results from the rapid ionization of a gas (Laroussi 2012 ).
Plasma is commonly obtained through subjecting gas to extremely high tempera-
tures, but it can also be obtained by passing gas through high-voltage electricity
(Rupf et al. 2011 ; Laroussi 2012 ; Traba et al. 2013 ). The latter method allows for
the gas to be ionized into plasma at a much lower temperature, one that is cool
enough to come in close contact with tissue without risk of thermal damage (Fig. 3 ).
Many different gases have been used for nonthermal plasma with the most common
being argon, nitrogen, helium, or some combination of these (Rupf et al. 2011 ;
Gasset et al. 2012 ; Traba et al. 2013 ). Nonthermal plasma itself is not a new
technology, but its application in inactivating bacteria, even within biofilms, is
extremely innovative (Ermolaeva et al. 2011 ) (Fig. 3 ). The generation of plasma at
mild temperatures facilitates direct contact with many surfaces on the body that
might harbor biofilms including teeth, skin, and even open wounds. Fortunately,
studies have already shown that nonthermal plasma poses little immediate danger to
skin cells, as the amount of UV light that is emitted is well below the threshold for
damage and the temperatures that are generated are apparently insufficient to cause
human cell damage (Lademann et al. 2011 ). While this does not provide complete
assurance, to our knowledge there do not seem to be any clinical data regarding
detrimental effects from exposure to nonthermal plasma and long-term negative
effects associated with repeated use.
Nonthermal plasma is an interesting tool because it is capable of eradicating
biofilms in two ways. First, there is a direct killing of the cells which make up the
biofilm involved, and second a physical removal of the biofilm mass from the
surface occurs. Plasma kills microorganisms through the production of highly