Page 306 - Biodegradable Polyesters

284 11 Electrospun Biopolymer Nanofibers and Their Composites for Drug Delivery Applications

the formation of core–shell nanofibers. Fibers in this approach are fabricated
from two separate solutions, minimizing the interaction between aqueous-based
biological molecules and the organic solvents for dissolving polymers. Thus,
the shell polymer not only contributes to sustained and prolonged release of
therapeutic agents but also plays an essential role in protecting the core ingredient
from direct exposure to outside biological environment and reducing toxicity
[57]. For example, coaxial electrospinning of PVP/zein was carried out smoothly
and continuously without any clogging of the spinneret with ketoprofen (KET) as
the model drug. Attenuated total reflectance Fourier transform infrared (FTIR)
spectra demonstrated both the sheath and core matrix had good compatibility
with KET owing to hydrogen bonding, thus providing a biphasic drug release
profiles with immediate release of 42.3% of the contained KET, followed by a
sustained release over 10 h of the remaining drug [58].
A variety of bioactive protein drugs have been available in large quantities as a
result of advances in biotechnology. Such availability has prompted development
of long-term protein delivery systems. The core–shell structured fibers fabricated
by coaxial electrospinning of PCL as the shell and BSA-loaded poly(ethylene
glycol) (PEG) as the core can release BSA sustainably for more than 30 days [59].
Zhang et al. reported the preparation of composite membranes of cationized
gelatin (CG)-coated PCL fibers where PCL formed the core section thereby
improving the mechanical property of cross-linked nanofibrous gelatin hydrogel
cationized by N,N-dimethylethylenediamine (CG), as shown in Figure 11.6. The
adsorption behavior indicated that the core–shell fibers could effectively immo-
bilize fluoresceinisothiocynate-labeled BSA (FITC-BSA) or FITC-heparin under
mild conditions. Furthermore, vascular endothelial growth factor (VEGF) could
be conveniently impregnated into the fibers through specific interactions with
the adsorbed heparin in the outer CG layer, with sustained release of bioactive
VEGF be achieved for more than 15 days [60]. Ji et al. also reported PCL-based
nanofibrous scaffolds with incorporated protein via either blend or coaxial elec-
trospinning technique. Coaxial electrospinning was demonstrated to be superior
to blend electrospinning with more uniform fiber morphology, homogeneous
protein distribution, sustained release profiles, and higher preservation of the
initial protein biological activity (75%) [61].
Liposomes, microscopic phospholipid bubbles with a bilayered membrane
structure, have been widely employed as pharmaceutical carriers. More recently,
many new developments have been reported in the area of liposomal drugs,
from clinically approved products to new experimental applications, with gene
delivery and cancer therapy still being the principal areas of interest [62].
However, the broader applications of liposomes in regenerative medicine are
severely hampered by their short half-life and inefficient retention at the sites
of applications. Therefore, coaxial electrospinning was applied in preparation of
PVA-core/PCL-shell nanofibers with embedded liposomes, which demonstrated
significant enhancement of mesenchymal stem cell proliferation as a promising
drug delivery system [63].