Biomedical Engineering Reference
In-Depth Information
13.5.2.4.2 SCAFFOLD FOR LIGAMENT AND TENDON TISSUE ENGINEERING. I n
order to design a bioresorbable scaffold for supporting and guiding regeneration
of ligament and tendon tissue, a number of design requirements have to be met.
Scaffold should be able to promote alignment of the cells and withstand repeti-
tive tensile loading, and should also promote the gradual growth of host ligament
tissue. Electrospun nanofi brous scaffolds are currently being explored as poten-
tial scaffolds for ligament and tendon repair [280].
Courtney et al. recently reported the use of electrospun poly(ester urethane)
urea (PEUU) in soft-tissue engineering. Their studies demonstrated that
electrospun - PEUU nanofi bers possess elastomeric property and can be well-
aligned. This attribute can be used to make biomimetic scaffolds for mechanically
anisotropic soft tissues [290].
In another study, Basher et al. studied the infl uence of PEUU mesh topogra-
phy (fi ber diameter and alignment) on cell growth and proliferation [287]. Their
studies demonstrated that PEUU surfaces allowed for cell adhesion and prolif-
eration. Further, the cells oriented themselves and were aligned in the direction
of fi ber orientation. Also, aligned nanofi bers showed improved cell adhesion with
increase in fi ber diameter and was highest for fi bers with the largest diameters.
Thus, PEUU aligned nanofi bers can be potential scaffolds for ligament tissue
engineering [291].
Lee et al. studied the infl uence of fi ber alignment and the effect of mechani-
cal strain direction on the behavior of human ligament fi broblast (HLF). HLF on
aligned polyurethane nanofi bers (PU) exhibited normal spindle shape and ori-
ented them along the length of the fi ber. Collagen content was used as a param-
eter to study the effect of cyclic uniaxial strain on HLF behavior. It was observed
that the cells aligned themselves in the direction of aligned nanofi bers and exhib-
ited 150-times more collagen production when uniaxial strain was applied in the
direction of cell alignment (that is, longitudinal stretching) as compared to
unstrained control when uniaxial strain was applied [92].
Using biomimetic approaches for designing scaffolds has been a popular
method in tissue engineering. However, interphase tissue engineering has
emerged as an interesting approach for subchondral defects, wherein the scaffold
has two different phases that mimic cartilage and bone. ACL connects to sub-
chondral bone through an interface wherein three distinct tissue regions—namely,
ligament, cartilage and bone—work in an integrated way such that load is dissi-
pated to bone with minimal stress on the interphase. Spalazzi et al. recently
reported a study which suggests that multi-tissue regeneration on a single scaffold
is possible through interphase tissue constructs. The study further suggests that it
is possible to mimic the multi-tissue organization present at the native ligament-
to-bone insertion site, and each phase of the triphasic construct could form the
corresponding tissue in which it has been inserted [292]. Knitted microfi bers are
considered to possess better mechanical strength, while nanofi bers have large
surface area. Combination of nanofi bers and microfi bers can provide a novel scaf-
fold for tissue engineering with enhanced properties. Hybrid nano-microfi brous
scaffold were fabricated by electrospinning PLGA nanofi bers on the surface of
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