Biomedical Engineering Reference
In-Depth Information
Natural polymers such as collagen have been studied as an elas-
tic scaffold created by cross-linking these polymers with chemicals
such as glutaldehyde, carbodiimide, and divinylsulfone.
8
,
9
Although
chemical cross-linking increases the elasticity of the scaffolds, these
chemicalsalsomaybecytotoxic.
10
,
11
Ontheotherhand,polyglycolic
acid (PGA) fibers were cross-linked with poly(
L
-lactic acid) (PLA)
to form a synthetic, biodegradable polymer scaffold for mechano-
activetissueengineering.
12
However,thissyntheticpolymerscaffold
exhibited significant, permanent deformation under cyclic mechan-
ical strain conditions.
13
-
16
The PLCL copolymer is composed of
asoftmatrixof
ε
-caprolactone moieties and hard domains con-
taining additional
L
-lactide units, differs a lot in their mechanical
properties depending on the monomer content, and exhibits a rub-
berlike elasticity in its physically cross-linked structure.
17
-
19
In
numerous studies, a PLCL copolymer prepared from 50 wt% of
L
-lactide and 50 wt% of
ε
-caprolactone was found to be highly elas-
tic and has been fabricated as a macroporous scaffold for tissue
engineering application.
20
In this chapter, we review the recent insight into PLCL scaf-
folds for tissue engineering, focusing on blood vessel and cartilage
regeneration.
27.2 Mechano-Active Scaffolds
27.2.1
Elastic Biodegradable PLCL Copolymer
A mechano-active polymer, a PLCL copolymer, was synthesized by
the ring-opening polymerization of
L
-lactide and
ε
-caprolactone in
the presence of Sn(Oct)
2
(Fig. 27.1). PLCL is composed of a soft
matrix of
ε
-caprolactone moieties and hard domains of
L
-lactide
units. The monomers used in this system differ greatly in mechan-
ical properties and time to reach complete mass loss; however, once
physically cross-linked in specific monomer ratios, the copolymer
system exhibits a rubberlike elasticity.
18
The structure of PLCL was
identified by
1
H NMR spectra in CDCl
3
(Fig. 27.1). The methine pro-
tons of the lactide unit appear as two singlets at
5.1-5.2 (a, a') as
a result of the sequence distribution of the lactyl and caproyl units,
δ
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