DESIGNING NANOFIBROUS SCAFFOLDS FOR TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 468

problem, approaches using contact guidance are being explored that would allow
the movement of cells along a desired direction. Neumann and co-workers dem-
onstrated alignment of myoblast in a single layer on parallel polypropylene fi bers
[267]. As discussed in a previous section, electrospinning offers the ability to
produce aligned fi bers, thus generating a scaffolding system that could fi nd use in
skeletal muscle tissue engineering. Riboldi et al. fabricated electrospun polyes-
terurethane microfi bers and explored their potential in skeletal muscle tissue
engineering [105]. The rationale for selecting polyesterurethane, a degradable
block polymer, was primarily due to its in vitro and in vivo biocompatibility and
elastomeric behavior. The results of their study demonstrated adherence and pro-
liferation of murine C2C12 muscle progenitor cells following differentiation on
microfi brous scaffolds as indicated by positive staining for myosin heavy chain
expression. Further, an elastic modulus of ten MPa was obtained that was compa-
rable to the elasticity of skeletal muscles. Thus, electrospun membranes show the
potential to be explored as scaffolds for skeletal muscle tissue engineering.

13.5.2.4 Ligament and Tendon. Ligaments and tendons are soft tissues
that play an important role in musculoskeletal biomechanics. Ligaments connect
bone to bone, whereas tendons connect muscles to bone. Both these tissues
possess high tensile strength, which is a characteristic feature of load-bearing
tissue [268] .
Ligaments and tendons, like most other musculoskeletal tissue, have a hierar-
chical structure that affects their mechanical behavior [269]. In addition, liga-
ments and tendons can adapt to changes in their mechanical environment due to
injury, disease, or exercise. Despite the similarity of function and metabolism,
ligaments are relatively more active than tendons [270].
Well-suited for their functional role, ligaments are tough fi brous cords, com-
posed of both collagen and elastic fi bers. The elastic fi bers allow the ligaments to
stretch to some extent. Water constitutes 60% of the wet weight of ligaments. The
remaining 40% is contributed by other major constituents of ligaments such as
collagen, proteoglycans, glycoprotein, and elastin. This ground substance is the
source of viscoelastic properties of ligament. Collagen type I and type III are the
major constituents, of which type I and III account for 90% and 10% of the wet
weight of ligaments [271 - 273] .
Tendons are complex structures. ECM of tendon comprises of water (55% of
the wet weight of tendons), proteoglycans ( 1%), along with cells and type I col-

lagen (85% of dry weight). Other collagens, such as collagen type III, V, XII, and
XIV are present in very lesser quantities, while decorin is the predominant type
of proteoglycan present in ECM of tendon.
Both ligaments and tendons have a complex structure, with a hierarchy of
collagen fi bers with specifi c orientation, which provides tensile strength to the
tissue. The hierarchical organization consists of collagen molecules, fi brils, fi bril
bundles, and fascicles that run parallel to the long axis of the tissue. Fascicles have
fi broblasts sparsely distributed and oriented along the direction of collagen fi bers
[274,275] .

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