3.3 Precipitation/Coacervation
This method utilizes the physical property of the polymer, whereby the polymer in
its solvent is dispersed into a non-solvent (a solvent that precipitates polymer) and
the nanoparticles are formed spontaneously during the phase separation, popularly
known as the Marangoni effect. The resultant particles can be stabilized by the use
of surfactants, and size can be controlled mainly by tuning the solvent:antisolvent
ratio. The formed particles are separated and purified by filtration or centrifugation
and washing. This route is suitable for encapsulating both hydrophilic and hydrophobic drugs, depending on the choice of solvents. The main advantage of preparing nanoparticles through precipitation is the narrow size distribution of the
particles [16, 35, 86, 87]. A study by Zhang et al. suggests that the copolymeric
carrier of starch/alginate/chitosan, prepared through coacervation is a better system
for the intestinal delivery of proteins and peptides [135]. Proteins such as gelatin,
collagen, and albumin are more often prepared by a modified precipitation or
coacervation technique [136].
3.4 Spray Drying
This is a fast, simple, and reliable technique for producing drug-loaded nanocarriers
in powdered form. The polymer as well as the drug are dissolved in their respective
solvents, blended, and then atomized under a stream of hot air, yielding small
droplets. During atomization, the solvent evaporates instantaneously and forms a
free-flowing powder. Desired particle size can be obtained by varying the
processing parameters such as size of the nozzle, spray flow rate, atomization
pressure, inlet air temperature, and extent of crosslinking [16, 35, 86, 87].
Alginate nanoparticles were successfully prepared using a spray drying technique, yielding submicron sized particles of mean diameter ~700 nm [135]. Spray
drying is the most commonly used encapsulation technique for food products [137].
Among the available biopolymers used for spray drying applications, the most
exploited ones for encapsulating food oils and flavors are carbohydrates, including
modified and hydrolyzed starches, cellulose derivatives, gums, and cyclodextrins;
and proteins such as whey proteins, caseinates, and gelatin [138, 139].In addition,
protein-loaded lipid/chitosan nanoparticle complexes were efficiently
microencapsulated using the spray drying technique for pulmonary delivery of
insulin [140].
Figure 5 illustrates how hydrophilic and hydrophobic drugs can be loaded within
biopolymers that are hydrophilic or hydrophobic by adopting these various methods
of synthesis.
260
D. Narayanan et al.
This method utilizes the physical property of the polymer, whereby the polymer in
its solvent is dispersed into a non-solvent (a solvent that precipitates polymer) and
the nanoparticles are formed spontaneously during the phase separation, popularly
known as the Marangoni effect. The resultant particles can be stabilized by the use
of surfactants, and size can be controlled mainly by tuning the solvent:antisolvent
ratio. The formed particles are separated and purified by filtration or centrifugation
and washing. This route is suitable for encapsulating both hydrophilic and hydrophobic drugs, depending on the choice of solvents. The main advantage of preparing nanoparticles through precipitation is the narrow size distribution of the
particles [16, 35, 86, 87]. A study by Zhang et al. suggests that the copolymeric
carrier of starch/alginate/chitosan, prepared through coacervation is a better system
for the intestinal delivery of proteins and peptides [135]. Proteins such as gelatin,
collagen, and albumin are more often prepared by a modified precipitation or
coacervation technique [136].
3.4 Spray Drying
This is a fast, simple, and reliable technique for producing drug-loaded nanocarriers
in powdered form. The polymer as well as the drug are dissolved in their respective
solvents, blended, and then atomized under a stream of hot air, yielding small
droplets. During atomization, the solvent evaporates instantaneously and forms a
free-flowing powder. Desired particle size can be obtained by varying the
processing parameters such as size of the nozzle, spray flow rate, atomization
pressure, inlet air temperature, and extent of crosslinking [16, 35, 86, 87].
Alginate nanoparticles were successfully prepared using a spray drying technique, yielding submicron sized particles of mean diameter ~700 nm [135]. Spray
drying is the most commonly used encapsulation technique for food products [137].
Among the available biopolymers used for spray drying applications, the most
exploited ones for encapsulating food oils and flavors are carbohydrates, including
modified and hydrolyzed starches, cellulose derivatives, gums, and cyclodextrins;
and proteins such as whey proteins, caseinates, and gelatin [138, 139].In addition,
protein-loaded lipid/chitosan nanoparticle complexes were efficiently
microencapsulated using the spray drying technique for pulmonary delivery of
insulin [140].
Figure 5 illustrates how hydrophilic and hydrophobic drugs can be loaded within
biopolymers that are hydrophilic or hydrophobic by adopting these various methods
of synthesis.
260
D. Narayanan et al.