DESIGNING NANOFIBROUS SCAFFOLDS FOR TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 450

calcium salt. Alginate is a non-toxic and immunologically inert polymer that bears
a structural resemblance to GAGs and hence, has been extensively explored in
tissue engineering applications [143,144]. Like other natural polymers, alginate is
hydrophilic and water soluble at room temperature. However, its use as an elec-
trospun non - woven fi brous scaffold is relatively recent, owing to the diffi culty
associated with its electrospinning. Electrospinning of alginate solution is rela-
tively challenging as gelation of alginate occurs even at low concentrations and
using very low solution concentration does not lead to fi ber formation [145]. In
addition, an increase in polymer concentration results in highly viscous solutions
that are diffi cult to electrospin. In an attempt to control the viscosity of alginate
solutions, Bhattarai et al. incorporated PEO in alginate solution along with a
surfactant [146]. The results of their study demonstrated that alginate could
be electrospun into nanofi bers when blended with PEO. Electrospun alginate-
based scaffolds are relatively easy to fabricate, process, and scale-up, and hence
have been extensively explored as a biomaterial [145,146]. Alginate can be co-
electrospun with multiple types of polymers to form more complex matrices, that
would more closely mimic natural ECM, and hence has the potential for use in
diverse tissue engineering applications [145,146].

13.4.1.2.3 CHITIN AND CHITOSAN. Chitin is a linear polysaccharide found in
marine crustacean shells and the cell walls of bacteria and fungi [147]. It is the
second most abundant natural polymer after cellulose [148] and has structural
resemblance to GAGs, such as chondroitin sulfates and hyaluronic acid, due to
which it has been considered as a biomaterial for tissue engineering scaffolds
[149]. Chitosan is a deacetylated (40-98%) derivative of chitin with repeating
units of (1 - 4) 2 - amino - 2 - deoxy - D - glucose and having a molecular weight in the

range of 300 KDa to 2000 KDa [148]. Chitosan, owing to its relatively better solu-
bility, has received more attention than chitin. However, like other natural poly-
mers, electrospinning of chitosan has been a challenging task because of its
polycationic nature in solution that leads to high viscosities.
Noh et al. studied the electrospinning of chitin with HFP as the solvent and
their results demonstrated that both chitin microfi bers and nanofi bers could be
synthesized using HFP as the solvent system [149].
Recently Geng et al., electrospun chitosan nanofi bers using acetic acid as the
solvent system. The rationale for the use of acetic acid is that it reduces the viscos-
ity of chitosan solution and increases the net charge on the jet [150]. Li et al.
investigated the effect of chitosan molecular weight on its ability to electrospin
along with the effect of an additive (PVA) on fi ber formation and morphology.
The study demonstrated that the ability of chitosan to be electrospun into nano-
fi bers increases with the decrease in molecular weight of chitosan in presence of
NaOH [151] .
Quaternised chitosan derivatives have been reported to possess better anti-
bacterial properties thereby enhancing their potential use as a wound dressing
material. Ignatova et al. studied electrospinning of quaternised chitosan (QCh)

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