Page 195 - Biodegradable Polyesters

7.3 Improving the Bioactivity of Electrospun Polyesters 173

great flexibility in synthesis, processing, degradation, and mechanical properties.
On the other hand, this polymer class has poor biological properties. Biological
activity of polyester scaffolds can be improved by blending the polyester with
a natural polymer. The hybrid electrospun scaffolds can combine the desired
characteristic of both kinds of polymers, enhancing their physico chemical and
biological properties. One example was the use of the copolymer poly(L-lactic
acid)-co-poly-(3-caprolactone) (PLCL) mixed with collagen for electrospinning.
PLCL made the collagen more easily processable through electrospinning.
On the other hand, the collagen incorporation rinsed the hydrophilicity
of the scaffolds and favored the development of MSC onto their surface.
Mitochondrial dehydrogenase activity, measured by 3-(4,5-dimethylthiazol-2-
yl)-5(3-carboxymethoxyphenyl)-2(4-sulfophenyl)-2H tetrazolium (MTS) assay,
showed that cellular growth on PLCL/collagen nanofibers was higher (80%) than
on PLCL nanofibers. This finding was attributed to the presence of an ECM pro-
tein and the greater wettability of PLCL/collagen scaffolds [145]. Gelatin is also a
natural polymer. It is derived from partial hydrolysis of natural collagen and main-
tains integrin binding sites for cell adhesion. The blend gelatin/polyglycolic acid
(PGA) was submitted to electrospinning to produce nanofiber scaffolds. HUVEC
and human artery smooth muscle cells (HUASMCs) were seeded onto the
scaffolds. The attachment of both types of cells was greater on PGA/gelatin than
on PGA nanofibers. In addition, it was observed which cells respond in different
ways to the gelatin, according to their concentration in the scaffolds. HUVECs
exhibited greater proliferation on the PGA/10 wt% gelatin nanofibers. Meanwhile,
a great number of HUASMC was observed on PGA/30 wt% gelatin scaffolds [146].
In addition to polymers, other natural molecules have been associated with
polyesters in order to improve their performance. Spirulina is a microalgae which
exhibits antibacterial and anti-inflammatory properties and is interesting for use
in skin tissue engineering, mainly in burn patients who need a greater protection
barrier. Because of this, spirulina biomass was associated with poly-D,L-lactic
acid (PDLLA) and electrospinning was performed. The biocompatibility in vitro
assays showed that the presence of spirulina improved the biological performance
of the scaffolds. These tests found that PDLLA/spirulina scaffolds exhibited more
adhered stem cells on their surface and greater cellular viability than PDLLA
scaffolds without spirulina [30].
Inorganic particles have also been used to produce electrospun scaffolds.
Hydroxyapatite (HA) is a calcium phosphate-based ceramic present in natural
bone, which has been evaluated for the production of bone scaffolds. Electrospun
scaffolds were produced from a blend of PLGA and nanosized HA. When MSC
were cultivated on the scaffolds, their osteogenic differentiation was favored.
The association of HA with polyester increased the cellular alkaline phosphatase
(ALP) activity and the expression of genes related with the osteogenic differentia-
tion in relation to PLGA without HA scaffolds. In addition, the content of calcium
was also increased in PLGA–HA fibers. The study indicates that PLGA–HA
scaffolds can be good substrates for bone regeneration. The study also proves