Antimicrobial Coatings to Prevent Biofilm Formation on Medical Devices - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 184

Poon and Burd 2004 ; Hidalgo et al. 1998 ; Lee and Moon 2003 ) (Table 1 ). Also,
with bandages, enough silver to inhibit biofilm formation has been shown to stain
tissue black. Those characteristics would tend to rule it out for contact lens use;
however, silver-impregnated contact lens cases are on the market (CIBA Vision). In
a study with silver impregnated etafilcon A lenses, Willcox et al. showed complete
inhibition at 20 ppm silver against P. aeruginosa and approximately 6 logs of
inhibition against S. aureus at 20 ppm silver (Willcox et al. 2010 ). At 20 ppm silver,
they only showed 1 log of inhibition against Acanthamoeba .
4.2.2 Compounds That Can Be Covalently Attached to a Contact Lens
and Inhibit Biofilm Formation
Fimbrolides (Furanones)
These are also quorum-sensing inhibitors. While these furanones were shown to
have toxicity to mammalian cells (see above under furanones), the safety of the
fimbrolide class of furanones attached to a contact lens was studied by a short-term
clinical assessment (Zhu et al. 2008 ) (Table 1 ). They found that the fimbrolide-
coated lenses reduced biofilm formation by 67-92 % for different bacteria and 70 %
for Acanthamoeba . They also saw no significant ocular response, by slit lamp, after
1 month in an animal model or overnight in humans.
Polyquaternium Compounds (Polyquats) and Polymeric Pyridinium
Compounds
These compounds generally consist of long-chain molecules with cationic ends and
can be attached to surfaces. The mode of action of these materials as well as the
limitation of this type of compound has been discussed above. Also, studies on
these compounds attached to surfaces show only about one log of biofilm inhibition
on contact lenses (Tiller et al. 2001 , 2002 ) (Table 1 ).
Cationic Peptides (Melimine)
A peptide was synthesized that contained portions of the sequences of the antimi-
crobial cationic peptides mellitin and protamine. The peptide was named melimine.
This peptide was covalently attached to contact lenses and was able to reduce
approximately 80 % of S. aureus and P. aeruginosa adhesion in vitro (Willcox
et al. 2008 ; Cole et al. 2010 ; Chen et al. 2012 ) (Table 1 ). A rabbit study showed a
reduction in contact lens-induced acute red eye and contact lens-induced peripheral
ulcers (Cole et al. 2010 ). A later study found that attachment of melimine to
etafilcon A lenses inhibited P. aeruginosa, S. aureus, A. castellanii , and Fusarium
solani by 3.1, 3.9, 1.2, and 1.0 logs, respectively (Dutta et al. 2013 ). However, there