Agriculture Reference
In-Depth Information
dissolved in the inner core or adsorbed to the polymeric coat. Alternatively, the
polymeric nanoparticles are formed by a polymeric matrix-type structure, called
nanospheres. In this case, the antimicrobial can be retained or adsorbed to the
structure (Vauthier and Bouchemal
2009
; Brandelli
2012
). Since polymeric cap-
sules are maintained by strong covalent bonds, they are more robust and stable than
liposomes, also in the dry form. The size and shape of the nanoparticles can be more
efficiently controlled using polymers, and the polymers can be modified with
different substances, adding new functional groups and properties.
Polymeric nanoparticles are primarily used to carry and deliver poorly water-
soluble drugs because of the hydrophobic nature of the nanoparticle core. Major
methods for preparation of polymeric nanoparticles are the solvent displacement
method and the emulsion polymerization method. The solvent displacement
method results in diblock polymeric nanoparticles consisting of a hydrophobic
core and a hydrophilic shell (Vauthier and Bouchemal
2009
). Several biodegrad-
able polymers have been used to form the hydrophobic polymeric core of
nanoparticles, including poly(lactic acid), poly(glycolic acid), poly(lactide-
co
-
glycolide), poly (
-caprolactone), and poly(cyanoacrylate), whereas PEG has
been frequently used as a hydrophilic segment. Linear polymers such as polyacryl-
amide, poly(alkyl acrylates), poly(methyl methacrylate), and poly(ethyl cyanoac-
rylate) are used to make nanoparticles by the emulsion polymerization method
(Zhang et al.
2010a
).
Biocompatible and biodegradable polymers have been used extensively in
biomedical and pharmaceutical sciences for controlled drug release. Polymeric
nanoparticles have been explored to deliver various antimicrobial agents, and
greatly enhanced therapeutic efficacy in treating many types of infectious diseases
has been reported (Huh and Kwon
2011
). Some distinctive properties of polymeric
nanoparticles make them an attractive platform for antimicrobial drug delivery.
Polymeric nanoparticles are structurally stable, and properties such as particle size,
zeta potential, and drug release profiles can be accurately adjusted by selecting
different polymer lengths, surfactants, and organic solvents during the synthesis. In
addition, the surface of polymeric nanoparticles usually contains functional groups
that can be chemically modified for targeted antimicrobial delivery. Polymeric
nanoparticles have been functionalized with lectins, which are proteins that bind
to carbohydrates present on most bacterial cell walls. The utilization of lectin-
mediated drug targeting is based on the fact that most cell surface proteins, and
many lipids in the plasma membrane, are glycosylated, and these glycans represent
ligands for lectins (Gavrovic-Jankulovic and Prodanovic
2011
). Poly(lactide-
co
-
glycolic) nanoparticles incorporating rifampicin, isoniazid, or pyrazinamide were
conjugated with the lectin wheat germ agglutinin (WGA) in order to reduce the
dosage frequency of antituberculosis drugs. The WGA-modified nanoparticles were
tested in animal models, showing potential for effective control of tuberculosis
through the oral and aerosol routes (Sharma et al.
2004
).
Among natural polymers, chitosan is the most studied for the development of
nanocapsules. This polysaccharide is a linear polymer composed of
D
-glucosamine
and
N
-acetyl-
D
-glucosamine residues linked in
ε
β
-1,4-configuration, resulting in a
