Civil Engineering Reference
In-Depth Information
interactions between the host carboxylate groups from microbial cellulose and guest
silver cations provided stable silver nanoparticles (average particle size about 13 nm)
with a controlled size distribution without particle aggregation. h e strong ion inter-
action is found to be ef ective for introducing silver cations to carboxylate groups,
resulting in immobilization of silver nanoparticles with high density [62]. h e
in-situ
synthesis of silver chloride (AgCl) nanoparticles in the three-dimensional nonwoven
network of microbial cellulose nanoi brils was carried out under ambient conditions,
where nanoporous microbial cellulose membranes functioned as nanoreactors. Growth
of the nanoparticles was readily obtained by alternating the dipping of microbial cel-
lulose membranes in solutions of silver nitrate and sodium chloride, followed by a
rinsing step. h e well-dispersed AgCl nanoparticle-impregnated microbial cellulose
membranes exhibited a high hydrophilicity and strong antimicrobial activity against
Escherichia coli
(Gram-negative bacteria) and
Staphylococcus aureus
(Gram-positive
bateria), which are general bacteria that are found on contaminated wounds [63].
In 2010, a facile method was developed to prepare a magnetic Ag nanocomposite
by spontaneous reduction of silver ions on a polydopamine surface. h is antimicro-
bial nanocomposite based on microbial cellulose was simply prepared by precipitating
magnetite in the presence of homogenized nanoi brous microbial cellulose, followed
by coating with self-polymerized polydopamine. h e 3D ribbon-like nanoi brillar net-
work of microbial cellulose was i rst homogenized with a ferric and ferrous salt mix-
ture in a high speed blender followed by soaking in dopamine solution, which results
a self-polymerized polydopamine layer on the microbial cellulose membrane. Since
the polydopamine surface is very ef ective for reducing silver ions, Ag nanoparticles
were incorporated into the dopamine-treated magnetic microbial cellulose when it
was soaking in silver nitrate solution. h e as-prepared Ag nanocomposite possesses
superparamagnetic properties along with an antimicrobial activity against both Gram-
positive and negative bacteria [64]. Yang
et al.
[65] and Wu
et al.
[66] demonstrated
microbial cellulose could also be utilized as the template for
in-situ
synthesis of sil-
ver nanoparticles (AgNPs) through chemical reduction. Yang
et al.
[65] studied the
ef ects of the microstructure of the microbial cellulose template, produced by dif erent
fermentation carbon sources, on the formation of AgNPs. h e results indicated that
the structure of the three-dimensional networks and a large amount of the nanosized
pores in the microbial celulose served as a stabilizing template for the formation of sil-
ver nanoparticles. h e mass content of the silver (0.86-1.60%), particle size of AgNPs
(5-14 nm), and the antimicrobial activity towards both
E. coli
and
S. aureus
bacteria
of the microbial cellulose/AgNPs composites varied depending on the dif erent micro-
bial cellulose templates used, mainly due to the dif erences in the microstructure of
the microbial cellulose template, especially the crystallinity and porous properties.
Patterned microbial cellulose might therefore attract more attention in the applica-
tion of wound healing. In Wu
et al.
[66] studies, uniform spherical silver nanoparticles
(10-30 nm) were generated and self-assembled on the surface of microbial cellulose
nanoi bers, forming a stable and evenly distributed Ag-nanoparticles-coated microbial
cellulose nanoi ber under ambient conditions. Strong adhesion between Ag nanopar-
ticles and microbial cellulose nanoi bers prevented leakage of Ag nanoparticles from
microbial cellulose network, and thus minimized the potential toxicity of nanoparticles.
h e AgNP-microbial cellulose hybrid nanostructure of ered excellent and sustainable
