Biomedical Engineering Reference
In-Depth Information
indicates that HA
10 wt% Ag composites reveal comparable/better bone
cell differentiation and better bone mineralization property than single
phase HA. This HA
−
10 wt% Ag composite provides excellent bactericidal
property against
E.coli
bacteria without compromising the
in vitro
cytocom-
patibility property of HA (Figure 7.13) [74]. In another study, silver
−
−
doped
hydroxyapatites Ca
10−x
Ag
x
(PO
4
)
6
(OH)
2
(0.0
C for
2 hours shows good antibacterial property, but MTT results of L929 fi bro-
blast cells cultured for 3 and 5 days show the cytotoxicity, when x
≤
×
≤
0.5), sintered at 1200
°
0.3 [75].
Among metal oxide powders, ZnO has already been studied extensively
and it demonstrates signifi cant growth inhibition of a broad spectrum of
bacteria. It is suggested that ZnO generates reactive oxygen species (ROS)
in presence of water and oxygen. This ROS reacts with bacterial cells and
kills the bacteria by damaging their cell membrane (Figure 7.14). The pro-
duction of H
2
O
2
is explained by the following set of equations [76].
>
ZnO
+
hv
→
e
−
+
h
+
h
+
+
H
2
O
→
•
OH
+
H
+
e
−
+
O
2
→
•
O
2
•
O
2
+
H
+
→
HO
•
(7.2)
HO
•
+
H
+
+
e
−
→
H
2
O
2
(
a
)
(
b
)
10
μ
m
20
μ
m
(
c
)
20
μ
m
Figure 7.13
SEM images revealing
E.coli
bacterial cell adhesion on substrate:
(a) HA
−
10 wt% Ag composite (sintered at 1200
°
C), (b) pure HA (sintered at
1200
C) and (c) negative control polymer disc after 4 hours of inoculation [74].
(With permission from Springer Science
°
+
Business Media)
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