Strategies to Prevent Bacterial Adhesion on Biomaterials - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 176

Water enters inside
the bacterial cell

Bacterial cell is destroyed

Figure 7.14 Schematic illustrating the cell membrane damage through ROS [75].

The generated negatively charged ions touch the cell surface, therefore,

hydroxyl ions and superoxides cannot enter into the cell membrane to
generate any toxicity. However, H 2 O 2 can go through the cell membrane
and cause toxicity [20]. In view of the fact that the radical formation takes
place on the surface of particles, antibacterial activity will be higher for
particles with greater surface area. Therefore, smaller

−

sized ZnO particles
reveal enhanced antimicrobial property [78, 79]. Available literature sug-
gests that ZnO is cytocompatible up to a certain concentration. According
to Atsuo et al., MC3T3

−

TCP/HA composite pro-
liferated without any cytotoxic effect up to a zinc content of 1.20 wt%,
while releasing zinc up to a concentration of 3.53 mg/L. Also, Zn 2+ stim-
ulates the alkaline phosphate activity and bone protein synthesis [80].
Bandopadhyay et al. synthesized the HA

− E1 cells cultured on Zn −

ZnO composites
with a varying concentration of ZnO from 0.5 to 3.5 wt%, and reported
cytotoxic response to OPC1 human osteoblast cells over 1.5 wt% ZnO con-
centration. Both TCP and HA samples showed good cell attachment after
5 days in culture for up to 1.5% ZnO doping [81].
Saha et al. prepared different composites of HA and ZnO with varing
content of ZnO (5-30 wt% ), and they optimized the composition show-
ing good antimicrobial property along with good cytocompatibility. In
order to investigate the antibacterial property of different HA

− ZnO and TCP −

ZnO com-
posites, E. coli and S. aureus were cultured for 4 hours on these compos-
ites. In order to assess the cytotoxity of HA

−

− ZnO composites, human

osteoblast like SaOS2 cells and mouse fi broblast L929 cells were cul-

tured. The results show that the antibacterial property increases with the
increased content of ZnO in the HA

−

ZnO composites (Figure 7.15). It was
concluded that HA with lower than 10 wt% ZnO is cytocompatible with
good bactericidal property. Figure 7.16 shows the antibacterial and cyto-
toxic effect of HA

−

like
SaOS2 cells, respectively. Florescence microscopy images in Figure 7.17
show the cytocompatibility of human osteoblast

− 20ZnO for E.coli / S.aureus and human osteoblast −

− like SaOS2 cells on dif-

ferent HA ZnO composites [82, 83]. After comparing the antibacterial and

cytotoxic effect of different HA

−

− ZnO composites, it is concluded that HA