Page 311 - Biodegradable Polyesters

11.3 Uniquely Encapsulated Drug/Biopolymer Nanofiber Systems for Drug Delivery 289

cell transfection and protein expression, and extracellular secretion of collagen
IV and laminin. Compared with pDNA polyplex infiltrated fibrous mats, pDNA
polyplex encapsulated fibers alleviated the inflammation reaction and enhanced
the generation of microvessels and formation of mature vessels. Although there
was no significant difference in the microvessel densities, compared with the sus-
tained release of individual pDNA, the combined delivery of both polyplexes of
basic fibroblast growth factor-encoding plasmid and vascular endothelial growth
factor-encoding plasmid promoted the generation of mature blood vessels. There-
fore, the integration of the core–sheath structure, DNA condensation, and multi-
ple delivery strategies provided a potential platform to achieve full vascularization
in engineered tissues and promptly regenerate blood vessel substitutes.

11.3.3
Electrosprayed Drug/Biopolymer Nanofibers

With polymeric micro- and nanoparticles being administered as oral, injectable,
inhalable, topical, and local drug delivery systems, increasingly common
techniques are employed to fabricate biodegradable polymeric micro- and
nanoparticles, such as solvent evaporation, spray-drying, single and double
emulsion, and coacervation. However, most of these methods are limited by some
disadvantages, such as low drug-loading efficiency, polydispersity in particle
size, and limitations in incorporating hydrophilic drugs and fabricating small
nanoparticles (below 100 nm). Moreover, inactivation or degradation of drugs,
especially for biomacromolecules, is possible owing to organic solvent exposure,
high shear stress, and temperature [1].
Electrospraying, a modified version of the electrospinning process, is a promis-
ing technique for preparation of micro- and nanoparticles suitable as drug delivery
systems. Similar to the electrospinning process, fabrication of drug-loaded poly-
meric particles via electrospraying can be performed using a blending solution
of polymer and drug in a sufficiently conductive solvent. By altering the solution
properties, for example, concentration, as well as processing parameters such as
flow rate and applied voltage, a continuous and charged jet can be broken down
into droplets, resulting in particles of different size and shape [76]. Blending of the
therapeutic agent in a polymer solution is the simplest way for drug encapsulation
into the electrosprayed particles in a single step [77]. It has been demonstrated
that electrospraying is a safe technique for processing several types of cells, and
the activity of proteins could be preserved during this process [78, 79].
An electrospray method is developed for preparation of beclomethasone
dipropionate-and salbutamol-sulfate-loaded biodegradable PLA nanoparticles.
PLA–drug nanoparticles with average diameters of about 200 nm are achieved
−1
in a stable cone-jet mode with a flow rate of 4 ml min , polymer concentration
of 1%, and ammonium hydroxide content of 0.05%. The results clearly indicate
that electrospraying is a potential method for producing polymeric nanopar-
ticles and efficiently encapsulating both hydrophilic and hydrophobic drugs
into nanoparticles [80]. Paclitaxel-loaded PLGA microspheres also have been