11.2 Nanoencapsulation
Nanoencapsulation of pesticides involves the formation of pesticide-loaded or
-entrapped particles having a diameter within the nano-range (Jafari 2017).
Nanocapsules, existing in miniscule size, range from 10 nm to 1000 nm. A
nanocapsule is a nanoscale shell made from a nontoxic polymer. They are vesicular
systems made of a polymeric membrane which encapsulates an inner liquid core at
the nanoscale. Nanoencapsulation is the coating of various substances within another
material at various sizes in the nano-range. The encapsulated material is commonly
referred to as the internal phase, the core material, the filler, or the fill, for instance,
pesticides. The active substances are usually dissolved in the inner liquid core. The
inner core can also consist of pesticide formulations or polymeric matrix, and active
ingredients may be absorbed by the polymeric shell. In this way the active
substances are encapsulated by nanocapsules spontaneously during the formation
of nanocapsules. The type of polymers used is of biodegradable polyester, as
nanocapsules are often used in biological systems. Poly-e-caprolactone (PCL),
poly(lactide) (PLA), and poly(lactide-co-glicolide) (PLGA) are typical polymers
used in nanocapsule formation. Other polymers include thiolated poly(methacrylic
acid) and poly(N-vinyl pyrrolidone). As synthetic polymers have proven to be more
pure and reproducible when compared to naturally occurring polymers, they are
often preferred for the construction nanocapsules. However, some natural occurring
polymers such as chitosan, gelatin, sodium alginate, and albumin are used in some
drug delivering nanocapsules. Other nanocapsule shells include liposomes, along
with polysaccharides and saccharides. Polysaccharides and saccharides are used due
to their nontoxicity and biodegradability.
11.2.1 Nanospheres
Nanospheres are defined as homogenous matrix systems wherein a dispersed or
dissolved active compound is adsorbed on the surface or entrapped within the
polymeric matrix structure through the solid sphere (Abreu et al. 2012; Liu et al.
2001, 2003). Nanospheres constitute the active nanocarrier system where the active
compounds are uniformly distributed and embedded into the polymeric matrix.
Nanospheres are a polymeric matrix of spherical shape that ranges in size between
10 and 200 nm in diameter. The nature of nanospheres can be amorphous or
crystalline, and they potentiate to protect the drug from chemical and enzymatic
degradation. Nanospheres can be divided into two categories: biodegradable
nanospheres and nonbiodegradable nanospheres. Biodegradable nanospheres
include albumin nanospheres, polypropylene dextran nanospheres, gelatine
nanospheres, modified starch nanospheres, and polylactic acid nanospheres,
polylactic acid (PLA), poly-D-L-glycolide (PLG), poly-D-L-lactide-co-glycolide
(PLGA), and poly-cyanoacrylate (PCA). In the case of nonbiodegradable
nanosphere, polylactic acid is the only polymer that is approved to be used as a
controlled-release agent.
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A. Kaur
Nanoencapsulation of pesticides involves the formation of pesticide-loaded or
-entrapped particles having a diameter within the nano-range (Jafari 2017).
Nanocapsules, existing in miniscule size, range from 10 nm to 1000 nm. A
nanocapsule is a nanoscale shell made from a nontoxic polymer. They are vesicular
systems made of a polymeric membrane which encapsulates an inner liquid core at
the nanoscale. Nanoencapsulation is the coating of various substances within another
material at various sizes in the nano-range. The encapsulated material is commonly
referred to as the internal phase, the core material, the filler, or the fill, for instance,
pesticides. The active substances are usually dissolved in the inner liquid core. The
inner core can also consist of pesticide formulations or polymeric matrix, and active
ingredients may be absorbed by the polymeric shell. In this way the active
substances are encapsulated by nanocapsules spontaneously during the formation
of nanocapsules. The type of polymers used is of biodegradable polyester, as
nanocapsules are often used in biological systems. Poly-e-caprolactone (PCL),
poly(lactide) (PLA), and poly(lactide-co-glicolide) (PLGA) are typical polymers
used in nanocapsule formation. Other polymers include thiolated poly(methacrylic
acid) and poly(N-vinyl pyrrolidone). As synthetic polymers have proven to be more
pure and reproducible when compared to naturally occurring polymers, they are
often preferred for the construction nanocapsules. However, some natural occurring
polymers such as chitosan, gelatin, sodium alginate, and albumin are used in some
drug delivering nanocapsules. Other nanocapsule shells include liposomes, along
with polysaccharides and saccharides. Polysaccharides and saccharides are used due
to their nontoxicity and biodegradability.
11.2.1 Nanospheres
Nanospheres are defined as homogenous matrix systems wherein a dispersed or
dissolved active compound is adsorbed on the surface or entrapped within the
polymeric matrix structure through the solid sphere (Abreu et al. 2012; Liu et al.
2001, 2003). Nanospheres constitute the active nanocarrier system where the active
compounds are uniformly distributed and embedded into the polymeric matrix.
Nanospheres are a polymeric matrix of spherical shape that ranges in size between
10 and 200 nm in diameter. The nature of nanospheres can be amorphous or
crystalline, and they potentiate to protect the drug from chemical and enzymatic
degradation. Nanospheres can be divided into two categories: biodegradable
nanospheres and nonbiodegradable nanospheres. Biodegradable nanospheres
include albumin nanospheres, polypropylene dextran nanospheres, gelatine
nanospheres, modified starch nanospheres, and polylactic acid nanospheres,
polylactic acid (PLA), poly-D-L-glycolide (PLG), poly-D-L-lactide-co-glycolide
(PLGA), and poly-cyanoacrylate (PCA). In the case of nonbiodegradable
nanosphere, polylactic acid is the only polymer that is approved to be used as a
controlled-release agent.
248
A. Kaur