Page 197 - Biodegradable Polyesters

7.4 Applications 175

were implanted in animal models of created knee defects, MSC-seeded PCL/PVA
nanofibers improved the healing of defects and the neo-tissue showed an ECM
very similar to the normal tissue. The findings suggest that these scaffolds can
serve as suitable grafts for the reconstruction of articular cartilage [149].
Electrospraying is a technique that is similar to electrospinning, controlled
by the same electrospinning parameters (voltage, feed rate, etc.). However, in
electrospraying, solutions with slow viscosity are employed. When the solution
is passed through the needle, it is exposed to a high-intensity electric field
which generates a jet. As the solution displays slow viscosity, the jet becomes
unstable, leading to the formation of droplets/particles [150, 151]. In their study,
Gupta and colleagues produced composite scaffolds by the association of HA
nanoparticle electrospraying and PLACL(poly(l-lactic acid)-co-poly(epsilon-
caprolactone))/Gelatin fiber electrospinning. The incorporation of HA on the
fibers by electrospraying helped to obtain a rough surface scaffold, offering the
best topography for cell adhesion and proliferation [152].

7.4
Applications

Scaffolds have been demonstrated to possess a crucial role in tissue regeneration.
Their structure should provide a biomimetic microenvironment where cells
can develop and form an organized tissue. Moreover, the scaffolds should have
adequate degradation kinetics and adequate mechanical properties, which
are able to maintain the physical structure until tissue regeneration is almost
completed. In addition, these properties should be similar to those of natural
tissue which requires regeneration [153]. The combination of polyester chemistry
and its processing by electrospinning provides pathways for the manufacture of
highly complex scaffolds. The polyester class offers a great absence of polymer
options for regenerative medicine. The various polyesters exhibit different prop-
erties, including mechanical strength, elasticity, and degradation rate, which are
evaluated before scaffold production, according to the requirements in the tissue
engineering area. Furthermore, intermediate characteristics can be adjusted
through the use of their copolymers. Some polyesters and their applications in
tissue engineering are listed in Table 7.2.
Polyesters have also been employed to produce electrospun scaffolds with
biomolecule controlled release. In these systems, biomolecules are incorporated
into polyester fibers and are then delivered from them in a controlled manner
in a specified area. Biodegradable polyesters have already been widely used for
different pharmaceutical formulations with encapsulated drug controlled release,
such as in micro/nanospheres, nanoparticles, and micelle. Besides biodegradabil-
ity, other advantages of polyesters, such as PLGA, are that they are commercially
available with different physicochemical properties and that the drug delivery
profile can be tailored by selecting a polyester with the appropriate properties
(such as molecular weight and ratio of monomers in copolymers). In addition, the