Biomedical Engineering Reference
In-Depth Information
with the increase in the organic phase ratio. The size of the particles did, however, fi rst decrease
and then increase as the BSA/PLA weight ratio decreased from 1:2 to 1:6. The spherical shape of
the particles was lost with a decreasing organic phase ratio and BSA amount. The particle yield was
in the range of 64.3-80.1%, and the BSA loading capacities were in the range of 74.2-91.4%. The
BSA encapsulation effi ciency that ranged between 22.9 and 80.6%, increased with an increasing
organic/aqueous phase ratio and decreased with an increasing BSA/PLA ratio. In the last stage,
high BSA/PLA ratio signifi cantly increased the BSA release rate, but a high organic/aqueous phase
ratio decreased the BSA release rate. The results showed that the physicochemical properties of
electrosprayed BSA-loaded PLA particles were affected by the organic/aqueous phase volume ratio
and the BSA/PLA weight ratio as well as the physical properties of emulsions.
Xie et al. applied the electrospraying technique to produce biodegradable polymeric micro-
and nanoparticles for pharmaceutical productions [42]. The solutions were prepared by dissolving
poly-lactic-
co
-glycolic acid (PLGA) polymer in acetonitrile (2-16%, w/v) with and without certain
amounts of paclitaxel (0-10%, w/w), surfactants Pluronic F127 (0-16%, w/w), and didodecyld-
imethylammonium bromide (0-2 mM). Three different experimental setups designed to study the
effects of particle formation are shown in Figure 11.12. In the confi gurations, setup (a) did not
use a ring electrode under the nozzle, and setup (b) did not use a glass chamber, but setup (c) was
designed with a glass chamber to control the solvent evaporation rate and to improve the collection
rate of the particles through a pneumatic conveying method. High voltages in the ranges of 5-10 kV
and 0-10 kV were applied to the nozzle and the ring, respectively. By varying the processing para-
meters, PLGA particles with a controllable morphology and size can be achieved through this tech-
nique. PLGA particles with an approximate size of 250 nm can be produced by adding organic salts
to increase the solution conductivity for electrospraying at a relatively high fl ow rate. The ability
to control the size of encapsulated drug particles provides a means to control the drug release
properties. SEM images in Figure 11.13 show the effects of polymer concentration on the particle
morphology and size. The size of the PLGA particles prepared by electrospraying decreased with
a reduction in the fl ow rate of the solution. The fl ow rates from 0.15 mL/h onward would form a
stable cone-jet spraying mode and produce particles with an approximate size of 900 nm in diam-
eter. Organic salt would increase the conductivity of the solution. With 1% salt concentration in
the solution, PLGA particles with an approximate size of 300 nm were produced to have relatively
good morphology at a fl ow rate of 0.2 mL/h. Higher fl ow rates could still produce PLGA particles
in a nanometer scale when a higher organic salt concentration was used to increase the conductivity.
Surfactant concentration had marginal effects on the size of particles and then was added in small
amounts to form nonagglomerated particles. The solution concentration did not affect the particle
size dramatically, except where the concentration was higher than 10%. Higher solution concentra-
tions also gave better surface morphology.
Ijsebaert et al. used electrospraying technique also to prepare pharmaceutical particles for inha-
lation purposes [55]. Methylparahydroxybenzoate (MPHB) was used as a model drug in the initial
experiments and beclomethasone dipropionate (BDP) was used as a drug for inhalation purpose.
The solution was prepared by dissolving MPHB and BDP in the ethanol solvent. Table 11.1 shows
the infl uence of the liquid fl ow and drug concentration on the particle size and width of the distri-
bution for the MPHB solution. The results showed that the size of the particles increased with an
increasing fl ow rate, and at the equal fl ow rates the particle size increased when the concentration
was increased from 0.5% to 3%. At a fl ow rate of 1.0 mL/h and a concentration of 0.5%,
the electro-
sprayed MPHB particles had an average size of 1.58 µm with a geometric standard deviation (GSD)
of 1.18. However, at a fl ow rate of 3.0 mL/h and a concentration of 3%, the average particle size was
4.55 µm with a GSD of 1.29. The experiments
showed that BDP resulted in similar particle sizes to
MPHB, and the mass of BDP was
in the range of 1.42-6 µg/L air. The experiment demonstrated
that the electrospraying technique is a promising method
to deliver antiasthma drugs to
patients.
The key advantages of electrospraying a drug solution for the purpose of inhalation are the ease of
aerosol production and the narrow particle size distribution.
