Biomedical Engineering Reference
In-Depth Information
Sureshkumar
et al.
have successfully developed a facile method to pre-
pare a magnetic silver nanocomposite [63]. h e 3D nanoi brous structure
of bacterial cellulose was homogenized with a ferric and ferrous mixture by
a high-speed blender. Magnetite nanoparticles were precipitated and incor-
porated into cellulose nanostructure by adjusting the homogenate to alka-
line pH. h e magnetic bacterial cellulose nanoi ber soaked in dopamine
solution will be coated with an adherent self-polymerized polydopamine
layer. Since the polydopamine surface is very ef ective for reducing silver
ion, silver nanoparticles were incorporated into the dopamine-treated mag-
netic bacterial cellulose by soaking in silver nitrate solution. h e magnetic
silver nanocomposite possesses a high antimicrobial activity against the
model microbes Escherichia coli and Bacillus subtilis. It also has potential
as a mild fermentation medium sterilizing agent so that a freshly prepared
LB medium shows no appreciable contamination at er incubating with Ag
nanocomposite for 4 h and removed by an external magnet.
As it was already mentioned above, silver nanoparticles could be strong
bactericidal agents but they also can be cytotoxic. Embedding them in a
polymer matrix may reduce their cytotoxic ef ect. In the study of Liu
et al.
,
silver nanoparticles in three average sizes were tested for their antibacterial
activities and cytotoxicity. Nanocomposites from a new waterborne poly-
etherurethane ionomer and silver nanoparticles were prepared without
the use of any crosslinker. It was observed that the antibacterial activity of
silver nanoparticles against Escherichia coli started at the ef ective con-
centration of 0.1-1 ppm, while that against Staphylococcus aureus started
at higher concentrations of 1-10 ppm. Cytotoxicity of silver nanoparticles
was observed at the concentration of 10 ppm. Silver nanoparticles with
smaller average size showed greater antibacterial activity as well as cytotox-
icity. h e PEU synthesized in this study showed high tensile strength, and
the addition of AgNPs at all sizes further increased its thermal stability. h e
delicate surface features of nanophases, however, were only observed in
nanocomposites with either small- or medium-sized AgNPs. h e PEU-Ag
nanocomposites had a strong bacteriostatic ef ect on the growth of E. coli
and S. aureus. h e proliferation of endothelial cells on PEU-Ag nanocom-
posites was enhanced, whereas the platelet adhesion was reduced. h e
expression of endothelial nitric oxide synthase gene was upregulated on
PEU-Ag containing small-sized AgNPs (30 ppm) or medium-sized AgNPs
(60 ppm). h is ef ect was not as remarkable in nanocomposites from large-
sized AgNPs. Overall, nanocomposites from the PEU and 60 ppm of the
medium-sized (5 nm) AgNPs showed the best biocompatibility and anti-
bacterial activity. Addition of smaller or larger AgNPs did not produce any
substantial ef ect in PEU, especially for the larger AgNPs.
