Page 314 - Biodegradable Polyesters

292 11 Electrospun Biopolymer Nanofibers and Their Composites for Drug Delivery Applications

protein encapsulation. In vitro release profiles measured using the Micro-BCA
assay indicated sustained release of BSA and lysozyme for more than 30 days.
The results of circular dichroism suggested that the secondary structure of
released BSA can be retained and the bioactivity of released lysozyme was found
to be more than 90%. Therefore, coaxial electrospray could be a very promising
approach to encapsulate biomacromolecules such as proteins, enzymes, DNA
plasmids, or living cells inside microparticles for controlled release drug delivery
applications [90].
With conventional methods for biodegradable particle production heavily rely-
ing on batch and emulsion preparation methods, Almería et al. developed a well-
controlled approach based on multiplexed electrospray to obtain a PLGA system
encapsulating amphiphilic agents such as doxorubicin, RHB, and RHB octadecyl
ester perchlorate. The results indicate that particles can be made encapsulating
the agent with high efficiency and be coated with emulsifiers in a single-step flow
process, which largely facilitates further functionalization for targeted drug deliv-
ery. Therefore, this synthesis technique is well suited for massive scale-up using
microfabricated, multiplexed arrays consisting of multiple electrospray nozzles
operating in parallel [91].

11.4
Conclusions and Outlook

Electrospinning has gained widespread interest as a potential polymer processing
technique for applications in drug delivery systems. By careful selection of
materials and processing conditions, either biodegradable or nondegradable
biopolymers can be used to control drug release via diffusion alone or diffusion
and scaffold degradation, and encapsulation of various suitable therapeutic
agents in electrospun nanofibers or nanoparticles has been effectively realized,
including antibiotics, anticancer drugs, proteins, and DNA. In addition, com-
bining different electrospinning techniques such as electrospraying, coaxial,
or emulsion electrospinning, a variety of different-structured drug/biopolymer
composites, for example, nanoparticle-encapsulated nanofibers and core/shell-
structured nanofibers or nanoparticles can be achieved to give finer control over
drug release kinetics, which show potential biomedical applications in wound
dressings, scaffolds, or devices for localized delivery of chemotherapeutics.
While electrospinning has emerged as a viable polymer processing technique
for applications in drug delivery systems, further investigations are required to
precisely characterize and optimize the pre-existing drug delivery systems and
develop new materials or methods for greatly improving the current product
properties. To date, most of the studies on drug release are performed in vitro,
while the capability of drug-loaded devices for clinical applications is essentially
needed to be confirmed in vivo. Therefore, it is urgently required for delivery of
therapeutic agents in a way very similar to the natural biological context through
electrospinning, especially for biomacromolecules such as DNA, RNA, or growth