SYNTHETIC ENROUTES TO ENGINEER ELECTROSPUN SCAFFOLDS FOR STEM CELLS AND TISSUE REGENERATION - Micro and Nanotechnologies in Engineering Stem Cells and Tissues - page 124

5.1.2.2 Gelatin Gelatin is a protein obtained from the partial hydrolysis of collagen
extracted from skin, bone, cartilage, ligaments, and so on. Gelatin is used as an
alternative source of collagen to design tissue engineering scaffolds, mainly because
of the lack of availability and high cost of collagen. Composite scaffolds of gelatin
with other biodegradable synthetic polymers have been well adopted by many
researchers. Moreover, these composite scaffolds with excellent biocompatibility,
improved mechanical, and physical and chemical properties overcome the obstacles
associated with the use of single natural polymers. 46 Interaction between cells and
the scaffold material depends on various physicochemical properties of the material
and particle size and surface properties that include topography, roughness, surface
energy, and wettability.
Three-dimensional nanofiber-gelatin-apatite composite scaffolds were fabricated
by Liu et al. 47 to mimic both the nanoscale native architecture and chemical
composition of natural bone ECM. With a new thermally induced phase separation
and porogen-leaching technique, these 3D nanofibrous gelatin scaffolds with well-
defined macropores were designed. The inorganic HAp deposited all along the 3D
porous structure is ideal for controlling surface topography and chemistry within
complex nanostructures. And it was shown that these scaffolds have excellent
biocompatibility and mechanical properties with enhanced osteoblast adhesion,
proliferation, and differentiation suitable for bone tissue engineering.

5.1.2.3 Silk Fibroin Silk fibroin is considered as the most promising natural
fibrous protein replacement for collagen in bone tissue engineering because of its
biocompatibility, slow biodegradation, and excellent mechanical properties. In the
past few years, two natural silk sources (e.g., silkworm silk Bombyx mori and spider
dragline silk Nephila clavipes) have been processed for making nanofibers via
electrospinning. 48-51 To improve the electrospinnability of silk protein solutions and
to avoid potential influences of hazardous organic solvents such as hexafluoroiso-
propanol, 48 hexafluoroacetone, 49 and formic acid 51 toward the biocompatibility of
the scaffolds, an all-aqueous electrospinning was attempted by Jin et al. 50 by
blending silk fibroin with PEO at a ratio from 1 : 4 to 2 : 3. Methanol treatment
of the electrospun scaffold renders water insolubility of the scaffold because of the
structural conformational change into native -sheet structure. Silk-based biocom-

posite nanofibers of HAp and bone morphogenetic protein 2 (BMP-2) were
fabricated by Li et al., 52 and an enhanced bone formation was observed by culturing
with human bone marrow-derived mesenchymal stem cells (hMSCs). It was
observed that the inclusion of BMP-2 and HAp with electrospun silk fibroin
nanofibers resulted in the highest calcium deposition and upregulation of BMP-2
transcript levels compared with other electrospun silk-based scaffolds.

b

5.1.2.4 Chitosan Chitosan, an amino polysaccharide derived from the structural
biopolymer chitin exists abundantly in crustacean shells (e.g., crabs) and plays a
key role as that of collagen in higher vertebrates. Chitosan retains a number of
salient features such as structural similarity to glycosaminoglycan found in
bone, osteoconductivity, excellent biocompatibility,

tailorable biodegradability,