Nanostructured Selenium – A Novel Biologically-Inspired Material for Antibacterial Medical Device Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 209

treated compared with planktonic bacteria in the solution. Thus, a further
study particularly targeting bacterial biofi lms, as shown in the following
section, needs to implemented to achieve more effi cient solutions to fi ght
implant infections.

8.4.3 Selenium Nanoparticles for Preventing Biofi lm

Formation on Polycarbonate Medical Devices

Unlike many metal-based antibacterial materials used in the healthcare
industry, selenium is a naturally occurring micronutrient needed for
a healthy lifestyle and is recommended for daily intake by the FDA. In
human beings, nutrition from selenium is achieved from 25 selenoproteins
or enzymes with selenocysteine at their active center [69], which are fun-
damental for a human's antioxidant defense system and other processes.
Importantly, a low selenium intake (less than 40 g per day) has been asso-
ciated with an increased risk of mortality, poor immune function, and
cognitive decline [70]. Clearly, thus, using nanoparticles of selenium is a
much more natural way to kill bacteria than synthetic antibodies.
Polycarbonate medical devices have been coated with nano-selenium
[71]. Two difference coating conditions were used in order to achieve various
sizes of selenium nanoparticles. Most of the selenium nanoparticles were
approximately 50-100 nm in diameter and they were well-distributed on the
polycarbonate surface (Figure 8.6). The concentration of selenium nanopar-
ticles on the polycarbonate surfaces were around 20 g/m 2 as assessed by
atomic absorption spectroscopy (AAS). Besides using an ASTM (American
Society for Testing and Materials) adhesion test, it was demonstrated that
larger nanoparticles had less adhesion strength to the underlying polycar-
bonate substrate than smaller selenium nanoparticles.
Most signifi cantly, in vitro studies on selenium-coated polycarbonate
showed that the selenium coatings on polycarbonate signifi cantly inhibited
Staphylococcus aureus growth 8.9% and 27% compared with an uncoated poly-
carbonate surface after 24 and 72 hours, respectively (Figure 8.7). Importantly,
this was accomplished without using antibiotics but rather with an element
(selenium) that is natural to the human body. Thus, this study suggests that
coating polymers (particularly, polycarbonate) with nanostructured selenium
is a fast and effective way to reduce bacteria functions that lead to medical
device infections. As polycarbonate samples coated under different condi-
tions had different abilities to inhibit bacterial growth, the concentration, size,
and coverage of selenium on polycarbonate needs to be optimized.

8.4.4 Preventing Bacterial Growth on Paper Towels

Lastly, in the hospital environment, hand washing has been identifi ed
as the most signifi cant manner of preventing the spread of microbial