Biomedical Engineering Reference
In-Depth Information
HV
GND
Figure 18.2
Basic set-up for electrospinning process includes a high-voltage source, polymer
solution, and a collection plate.
In addition to the polymer selection for electrospinning, process parameters greatly
influence the fiber fabrication. Polymer weight, solvent properties, applied electrical poten-
tial, polymer solution flow rate, distance between spinneret and collector, motion of the
grounded target, as well as temperature, humidity, and air velocity have an effect on the
electrospun fibers. Nanofiber diameter, surface morphology, mechanical properties, porosity,
and pore-size distribution greatly depend on these parameters [26]. Depending on the motion
of collector target, different types of fibers can be created. Stationary collectors result in
random nanofibers, while rotating targets, such as a rotating drum and wheel-like bobbin or
metal frame result in fiber alignment and fabrication of tubular nanofiber scaffolds. When
two conductive substrates are separated by a void gap, this can result in the deposition of
aligned nanofibers [26]. Synthetic, natural, and blend combinations of polymers have been
used to create scaffolds in the form of nanofibers for skin regeneration.
Natural Polymers
Natural polymers such as collagens, elastin, and fibrinogen make up much of the body's
native ECM; therefore it is logical to use such polymers to construct synthetic ECMs.
Naturally derived materials come in the form of polysaccharides or protein fibers [32].
Though natural polymers are criticized for lower mechanical properties, difficult process-
ibility [32], and batch to batch variation [33], they possess inherent characteristics of excel-
lent biocompatibility, nontoxic degradation products, and have similar architecture to native
ECM [32, 33].
Collagen
Collagen is the most abundant natural protein found in the body that helps maintain struc-
tural integrity of tissues [34]. Due to its capability to numerous cell types and strong
mechanical ability, the polymer makes a suitable environment for cell growth. Collagen has
a long history in the design of skin substitutes [35]. Crosslinking type II collagen [36] or
