Nanostructured Selenium – A Novel Biologically-Inspired Material for Antibacterial Medical Device Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 211

infections [72, 73], with hand drying as the critical last stage of the hand
washing process. Among the three frequently used methods to dry hands
(hot air dryers, cloth towels and paper towels), paper towels have been
recognized as the most hygienic method of hand drying [74, 75]. However,
in some circumstances, such as for paper towels hanging in sink splash
zones or those used to clean surfaces, they have been considered as poten-
tial sources of bacteria contamination [76]. Besides paper towels that are
used for hand drying, there are concerns for many other paper products
in terms of bacteria contamination or infections, for example, food wrap-
ping in the food industry [77], wallpaper in a doctor's suite, fi lter paper in
water purifying system [78] and so on. All of these materials are prone to
bacteria growth and, thus, are sources for continual contamination.
One of the most promising approaches towards preventing infection is
coating paper products with antimicrobial materials. For example, Wenbing
Hu and his colleagues introduced antibacterial properties to fi lter paper
by coating the paper with graphene oxide, which showed about a 70%
inhibition to Escherichia coli growth after 2 hours. However, the graphene-
based paper had mild cytotoxicity resulting in 20% of healthy mammalian
A945 cell death after 2 hours [79]. Chule et al. studied the antibacterial
activities of ZnO nanoparticle-coated paper [80] and results showed a sig-
nifi cant decrease in bacteria counts after 24 hours. Besides ZnO nanopar-
ticles, silver nanoparticles have also been loaded on fi lter paper for
antibacterial purposes, processing strong antibacterial properties.
But one major problem for ZnO and silver nanoparticles and other
metal-based materials is their toxicity to healthy cells due to the gener-
ation of reactive oxygen species [81, 82]. Those materials may result in
severe health problems when they are used as coatings on paper products
such as for food wrapping or clinical applications.
Therefore, selenium nanoparticles were coated on normal paper
towel surfaces, introducing signifi cant effectiveness towards prevent-
ing Staphylococcus aureus growth on the paper surfaces [83]. As shown
in Figure 8.8a, selenium nanoparticles were well distributed and com-
pletely covered the surface. Some of the selenium nanoparticles were also
observed in the fi ber structure on the top surface. Diameters for most of
the selenium particles were around 50 nm. According to AAS results, the
concentration of the selenium nanoparticles on the coated paper towel
surface was 69.00 g/m 2 . There were no particles observed for the uncoated
paper towel (Figure 8.8b).
Based on the bacterial assays, the selenium-coated paper towel samples
signifi cantly inhibited Staphylococcus aureus biofi lm formation compared
with uncoated paper towel samples. As seen in Figure 8.9, the selenium-
coated paper towels had 88.6%, 88.9% and 88.8% less bacteria attached
than the uncoated paper towels after 24, 48 and 72 hours, respectively.
Moreover, from the 24 hour culture time to the 48 hour culture time,
there was an increase in bacteria numbers on the uncoated paper towel