BIO-HYBRID 3D TUBULAR SCAFFOLDS FOR VASCULAR TISSUE ENGINEERING—A MATERIALS PERSPECTIVE - Biomaterial Applications: Macro to Nanoscales - page 19

This process allows for the formation of nanofibers composed of polymer
blends, natural and synthetic, all done in a rather straightforward, cost
effective setup [17]. Therefore, an increased emphasis is given to review
electrospun bio-hybrid scaffolds, their mechanical integrity, biocompat-
ibility, and native cell adhesion and proliferation in this chapter.
2.2 BIO-HYBRID VASCULAR GRAFT BASED ON COLLAGEN/
SYNTHETIC POLYMERS
Since the introduction of biopolymers in vascular tissue engineering, col-
lagen has been a favored material due its prevalence in native vascular
make-up. It is made up of groups of fibrous proteins and naturally pro-
duced by mammalian cells. It is also one of the most plentiful proteins
found in human body. There are almost 28 different types of collagen in
the human body [38]. Collagen is a preferable biopolymer because it's
low antigenicity, low inflammatory and cytotoxic response, and desirable
biological and hematological properties [39]. Collagen has been used in
various biomedical applications due to its biocompatibility and biodegrad-
ability [40]. As mentioned previously, it is a main component in the blood
vessel matrix-structure. Therefore, researchers have strived to compose
vascular grafts using collagen and gelatin (denatured collagen) with or
without other biodegradable polymers. The basic structure of collagen is a
three-parallel polypeptide chains formed by glycine, proline and hydroxyl
proline repeating units arranged in a triple helix structure [41]. The me-
chanical integrity of collagen type I can be different than collagen type III
or others and different tissue types have different types of collagen. In ad-
dition, collagen origin can also play a role in the final characteristics of the
collagenous tissue-scaffolds derived from animal or cadaver tissues [11].
Being a vascular matrix protein, researchers started to fabricate hy-
brid grafts made of collagens and biodegradable synthetic polymers to
impart bioactivity and to prevent scar-tissue fibrosis. Weinberg and Bell
have incorporated collagen with Dacron (nonbiodegradable) to create a
model for an artificial blood vessel in vitro [42]. Thereafter, the biode-
gradable grafts were introduced since they would degrade in vitro and
in vivo as the native tissue formation starts. Widely used aliphatic poly-
esters in tissue engineering applications take several months to a few
years to degrade. The biodegradation and cell-interaction characteristics