Agriculture Reference
In-Depth Information
acid) nanofibers have been reported, where fibers prepared with 1 % PLA showed a
smooth morphology, but a “bed-in string” morphology was observed by increasing
PLA concentration to 3 %.
The nanofibers have a large diffusion potential for antimicrobials due to the high
surface to volume ratio. Also, different drug-loading modes in the nanofiber surface
can be obtained. Antimicrobials can be loaded on the surface of the nanofiber by
simple physical adsorption generally provided by van der Waals interactions and
hydrogen linkages. Alternatively, adsorption of the drug-loaded nanoparticles in the
surface of the fibers can be done. An assembly as layer by layer on the cover allows
a few nanometers by deposition of polyanions such as heparin (Yoo et al.
2009
).
Another issue associated with the use of nanofibers is the possibility and use of
surface modification methods to extend their applications (Yoo et al.
2009
). Several
methods of modifying synthetic polymers are used to improve the ability of drug
diffusion from nanofibers. Wet chemical methods can be used, as illustrated by the
treatment of PLA nanofibers with NaOH to increase the ability to bind Ca (which
has been investigated for bone regeneration). Reaction of diamines with polyester
nanofibers creates more loading capacity by charged surface adhesion. Plasma
treatment is a technique that has been also used. For example, plasma treatment
with oxygen or air can produce ammonium carboxyl or amino groups on the
nanofiber surface. Another example is the treatment of PCL nanofibers with
argon or air plasma to increase the number of carboxyl groups increasing the
adhesion and proliferation of cells. The introduction of functional groups on the
surface of nanofibers can be made by graft polymerization (copolymer). In general,
UV or plasma treatment is used to generate free radicals for polymerization. One
example is the development of modified polyurethane nanofibers 4-polyvinyl
bromide hexylpiridinium, resulting in modified nanofibers with high antimicrobial
activity against
S. aureus
and
E. coli
. Another way to obtain surface-modified
nanofibers is the co-electrospinning, where the active agents are present in the
polymer solution. The conjugation of the antimicrobial peptide (Ser-Glu-Glu)
3
terminally conjugated with polyethylene oxide resulted in a functionalized
nanofiber with peptide orientation to the surface.
Application to compress for wound dressings has been a proposed utilization for
nanofibers. Multifunctional nanofibers embedded with epidermal growth factor and
antibiotics may provide antibacterial protection while stimulating healing
(Schneider et al.
2008
). Silk fibroin nanofiber incorporating the antimicrobial
peptide cecropin B can reduce the counts of
S. aureus
and
E. coli
in more than
90 % (Bai et al.
2008
). Surface modification of polyurethane nanofiber with
quaternary ammonium resulted in a material with a highly effective antimicrobial
activity, inhibiting both
S. aureus
and
E. coli
over 99.9 % (Yao et al.
2008
).
Nanofibers may have also potential to delivery antimicrobials in food systems.
Lysozyme, which is widely employed as a food preservative, has been encapsulated
into nanofibers. Lysozyme was incorporated into poly(
-caprolactone) and poly-
ethylene oxide (90:10) nanofibers, and the release was 87 % over 12 days (Kim
et al.
2007
). Chitosan nanofibers were used to encapsulate lysozyme via cross-
linked enzyme aggregates as used for continuous antimicrobial application. The
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