Biomedical Engineering Reference
In-Depth Information
hyde. The study demonstrated that although better mechanical properties were
obtained for cross-linked scaffolds when compared to non cross-linked scaffolds,
the mechanical properties of cross-linked scaffolds were less than that of native
collagen type II fi bers [117] .
The drawback associated with collagen fi bers is their rapid degradation in the
physiological environment. This has been overcome by cross-linking of collagen
fi bers using cross-linkers such as glutaraldehyde, formaldehyde, epoxy com-
pounds and zero length cross linkers such as carbodiimide [39,117,118]. Although
the electrospun collagen fi bers do not fully recapitulate the native collagen fi bers,
they still hold promise for tissue engineering applications.
13.4.1.1.2 GELATIN. Gelatin is a denatured form of collagen obtained by
subjecting the collagen source (bone, tendon or skin) to acid or alkaline pre-
treatment [119]. It is a relatively inexpensive substitute for collagen. Being a
derivative of collagen, it has a polypeptide nature and possesses RGD peptides
required for cell adhesion. However, unlike collagen, gelatin contains multiple
oligopeptides of diverse molecular weight. Use of gelatin in drug delivery applica-
tions [120], wound dressing applications and as a food additive has been known
for many years [121,122]; however, its use as a biomaterial for electrospinning is
relatively recent.
Gelatin is soluble in water at room temperature; however, gelatin contains
ionizable groups that form hydrogen bonds in the aqueous environment that
makes electrospinning of gelatin quite challenging. Being a biopolymer with
strong polarity, gelatin needs to be dissolved in highly polar organic solvents to
enable electrospinning. Huang et al. demonstrated the use of a highly polar
solvent 2, 2, 2-trifl uoroethanol (TFE) for electrospinning of gelatin [123]. Huang
et al. also validated that the mechanical performance of gelatin nanofi bers
was infl uenced by the fi ber diameter as well as fi ber morphology. The fi nest
fi brous mat without beads was obtained at a relatively higher concentration
of gelatin and this mat exhibited better mechanical strength as compared to
relatively thick but beaded fi bers [123]. Ki et al. examined the stability of gelatin
in formic acid, and hence, its effect on the morphology of electrospun gelatin
nanofi bers [124]. They reported the formation of gelatin fi bers having diameters
in the range of 70-170 nm with formic acid showing no signifi cant effect on gelatin
fi bers [124] .
The hydrophilicity of gelatin causes loss in physical integrity when exposed to
water; hence, there is a need for cross-linking gelatin fi bers to enhance their
mechanical strength and stability for their use as scaffolding systems. Zhang et al.
reported the electrospinning of gelatin nanofi bers that were cross-linked post
synthesis with glutaraldehyde vapours (GTA) at room temperature for three
days. There results demonstrated that the cross-linked nanofi brous membranes
maintained their structural integrity after being immersed in water for six days.
Further, these membranes were non-cytotoxic and exhibited enhanced thermal
stability and mechanical strength [125]. Hence, cross-linked nanofi bers show
potential to be used in tissue engineering applications.
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