Biomedical Engineering Reference
In-Depth Information
100
Under UV light
In darkness
80
60
40
20
0
Stainless
steel
DLC TiO
2
-DLC
(0.1 g/L)
TiO
2
-DLC
(0.5 g/L)
TiO
2
-DLC
(1.0 g/L)
FIGURE 2.40
Antibacterial activity of the stainless steel-coated and uncoated with a-C:H and a-C:H(TiO
2
) films in different
TiO
2
concentrations. (Reprinted with permission from Marciano et al.,
J. Coll. Interf. Sci.
, 340, 87, 2009.)
performed against
Escherichia coli
, and the results were compared to the bacterial adhesion
force to the studied surfaces. As TiO
2
content increased,
I
D
/
I
G
ratio, hydrogen content, and
roughness also increased. The films became more hydrophilic, with higher surface free
energy, and the interfacial energy of bacteria adhesion decreased. Experimental results
show that TiO
2
increased the a-C:H bactericidal activity (see Figures 2.40 and 2.41). Pure
a-C:H films were thermodynamically unfavorable to bacterial adhesion. But the chemical
interaction between the
E. coli
and the studied films can be increased for the films with
higher TiO
2
concentration. As TiO
2
bactericidal activity starts its action by oxidative dam-
age to the bacteria wall, a decrease in the interfacial energy of bacteria adhesion causes an
increase in the chemical interaction between
E. coli
and the films, which is an additional
factor for the increasing bactericidal activity. Another study of
E. coli
on silver-doped a-C:H
also showed an increase in bactericidal activity [147].
(a)
(b)
(c)
(d)
(e)
4 µm
4 µm
4 µm
4 µm
4 µm
(f )
(g)
(h)
(i)
(j)
4 µm
4 µm
4 µm
4 µm
4 µm
FIGURE 2.41
SEM images of
E. coli
in direct contact with (a) stainless steel, (b) a-C:H, (c) 0.1 g/L a-C:H(TiO
2
), (d) 0.5 g/L
a-C:H(TiO
2
), and (e) 1.0 g/L a-C:H(TiO
2
) films in darkness; and (f) stainless steel, (g) a-C:H, (h) 0.1 g/L a-C:H(TiO
2
),
(i) 0.5 g/L a-C:H(TiO
2
), and (j) 1.0 g/L a-C:H(TiO
2
) films under UV light. (Reprinted with permission from
Marciano et al.,
J. Coll. Interf. Sci.
, 340, 87, 2009.)
