Nanostructured Selenium – A Novel Biologically-Inspired Material for Antibacterial Medical Device Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 205

with bacteria remains largely unknown and there is not a material that is
well established and widely accepted for antibacterial purposes.

8.3 Selenium and Nanostructured Selenium

Selenium belongs to the group of metalloids from the chalcogen family
in the periodic table of elements. It exists in a range of oxidation states
from 2. Selenium has various allotropic forms, such as the red

amorphous form, black vitreous form, three ( a , b , g ) of red crystalline
monoclinic forms and the gray/black crystalline hexagonal form [38-41].
Commercially, selenium is produced as a byproduct of copper refi ning. It
is used in electronics, glass, ceramics, steel and pigment manufacturing
[42]. Selenium is naturally found in humans and animals as a part of sele-
noproteins, which play an important role in antioxidant defense systems,
thyroid hormone metabolism and redox control of cell reactions [43].
Previously, selenium and its compounds were studied for reducing or
preventing cancers. It has been shown that high levels of selenium in the
blood (~154 μg/ml) correlate with reduced numbers of cancers includ-
ing pancreatic, gastric, lung, nasopharyngeal, breast, uterine, respiratory,
digestive and gynecological cancer [44]. Moreover, people living in areas
of low soil selenium (lower than 0.05 ppm) and people with decreased
plasma selenium levels (below 128 ng/ml) have higher cancer incidence
and/or cancer mortality [45, 46]. Many in vitro studies also demonstrated
the inhibitory effects of selenium on the growth of many cancerous cell
lines [47-49]. However, the mechanisms of selenium-related chemopre-
vention are complex and remain largely unknown [50].
Recently, as the organic forms of selenium have been studied for their
biological effects, the elemental selenium nanoparticles have also drawn
some attention in many studies [51]. Various methods of synthesizing sele-
nium nanoparticles have been reported [52-56]. In a easy and quick pre-
cipitation method, selenium nanoparticles were synthesized by reducing
sodium selenite with glutathione [57, 58]. The hypothesized mechanism
below was based on several reactions involving sulfur, because selenium
and sulfur are in the same group in the periodic table.

+ 6 to −

(a) 4 GSH + Na 2 SeO 3 → GSSeSG + GSSG + 2NaOH

(b)

G

→

OH - GSOH + GSSe -

Se S +

G S

(c) GSSe − → GS − +Se

(d) GS − + GSOG → GSSG + OH −

(8.1)