Control of Polymicrobial Biofilms: Recent Trends - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 336

support for localized delivery to species within the polymicrobial biofilm and a
release of a much greater concentration of the antimicrobial (Wilkinson et al. 2011 ).
For instance, attaching nitric oxide to silica nanoparticles has proven to be
extremely potent at killing Gram-positive and Gram-negative species
within biofilms, with P. aeruginosa and E. coli being most susceptible
(Hetrick et al. 2009 ). Similarly, there are nanoparticles that can carry more than
one antibiotic, for simultaneous release, and different combinations of multiple
drugs on each particle can be used to overcome the antimicrobial resistance
mechanisms observed in biofilms and resident species (Pelgrift and Friedman
2013 ).
Perhaps one of the more interesting uses of nanoparticles is based upon the use of
liposomes. Liposomes are artificial vesicles composed of a phospholipid bilayer
that can be used to encapsulate specific molecules of interest (Zhang and Granick
2006 ). Liposomes can thus be used for the delivery of antimicrobials to bacteria and
even bacteria in biofilms (Jones 2005 ) and have a key benefit that water-soluble or
oil-soluble compounds can be delivered to targeted biofilms and the surfaces on
which they reside. Unfortunately, liposomes also have the tendency to coalesce
(fuse with one another) and have limited shelf life. Work by Zhang and colleagues
( 2010 ) demonstrated that nanoparticles could be used to stabilize liposome struc-
ture (increasing shelf life) and also prevent them from coalescing.
4.4 Antimicrobial Surfaces and Coatings
One of the most vital components to the development of any biofilm is an appro-
priate surface to adhere, for without such a surface the complex network of cell-cell
interactions can never occur. Indeed, surface properties have been of particular
interest for exploitation in the field of marine biofouling (Tribou and Swain 2010 ;
Banerjee et al. 2011 ; Scardino and de Nys 2011 ). Conceivably, rendering a surface
resilient to the development of a conditioning film and/or toxic to a bacterium will
make it non-colonizable and is likley more effective than controlling established
recalcitrant biofilms. While there are many examples of variations of this technol-
ogy, a couple of interesting approaches will be briefly described.
Much effort has been invested into the design of surfaces that can prevent
biofilm formation. There is a vast array of surface types that use different strategies
to achieve anti-adhesion of bacterial cells. One such option is to coat a surface
directly with an antibiotic. For instance, coating surfaces with vancomycin and
gentamicin has been shown to be effective for prophylactic purposes (Radin
et al. 1997 ; Alt et al. 2006 ). Such coatings can be made for controlled release
over a relatively short period of time or covalently bonded to the desired surface for
long-term protection (Lucke et al. 2003 ; Edupuganti et al. 2007 ). Although what
could conceivably be considered a generally sound approach, this strategy is
inadequate against bacteria that are already resistant to the antimicrobial agent.
To overcome this shortcoming, Inbakandan and colleagues found that silver-coated