Soft Matter Composites Interfacing with Biomolecules, Cells, and Tissues - Bioinspired Approaches for Human-Centric Technologies - page 54

In the electrospinning technique, a high electric field is applied in order to create
fibers with a diameter ranging from a few nanometers to larger than 1 m. A basic

electrospinning apparatus consists of a syringe filled with the target polymer
solution, a syringe pump, a high voltage supply, and a collector. The metallic
needle of the syringe serves as electrode to induce electrical charges within the
solution, under the influence of a strong electrostatic field. When the charge
repulsion overcomes the surface tension of the polymeric solution, a charged
polymeric jet is formed and is accelerated towards the collector. During the flight
of the jet, the solvent evaporates and polymeric nanofibers are collected.
The electrospun fiber mats have high surface area, much higher than films of
hydrogel materials or even that other fibrous dressing made in conventional ways.
In this way, that can assure optimized exude absorption, moisture permeation, and
gas transport (Zhang et al. 2005 ). On the top, this technique is highly versatile in
terms of used materials. Indeed, electrospun fibers can be made of natural or
synthetic polymers or different combinations of both. Finally, the electrospun
mats can attain different functionalities by tuning the different polymer concen-
trations and by incorporating in the nanofibers different drugs, active biological
molecules, antibacterial agents, etc.

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2.7 Electrospun Mats Without Active Agents

Natural polymers, such as polysaccharides and proteins are the most common
electrospun materials used for treatment of skin wounds due to their inherent
properties that assist the process of healing. In the majority of the cases, they are
used in combination with synthetic polymers due to their intrinsic low processabi-
lity (e.g., poor solubility and high surface tension) (Lee et al. 2009 ) but also in order
to enhance the mechanical properties and tune the morphological features of the
produced mats. In particular, the polysaccharide chitosan has demonstrated intrin-
sic hemostatic and antibacterial properties, and for this reason many research works
have been focused on its electrospinning. Since it cannot be electrospun alone, it is
used in combination with other polymers. For example, an electrospun matrix of
chitosan, collagen, and polyethylene oxide was fabricated followed by further
cross-linking using glutaraldehyde vapor. Animal studies showed increased
wound-healing rate using this matrix as wound dressing compared to gauzes and
commercial collagen sponges (Chen et al. 2008 ). Also the electrospun combination
of chitosan and silk fibroin has demonstrated good antibacterial activity and
biocompatibility using murine fibroblasts. Although only in vitro tests were
performed, the results suggest that such composite nanofibrous membranes can be
used in wound healing (Cai et al. 2010 ). A successful combination of electrospun
nanofibers includes chitosan, hydroxybenzotriazole, and polyvinyl alcohol blend.
This underwent cytotoxicity tests and was found nontoxic to human fibroblast cells,
suggesting its suitability as wound dressing material (Charernsriwilaiwat
et al. 2010 ). A natural polysaccharide that has shown great potentiality for the