Polysaccharides as Nanomaterials for Therapeutics - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 134

in the preparation of chitosan nanoparticles is a result of both being
non-toxic and of the ability to modulate particle size, morphological
properties and surface charge mainly by controlling the chitosan
to TPP weight ratio [72]. The first TPP cross-linked chitosan
nanoparticles for drug delivery were developed by Alonso's group
[73]. The method was based on a principle reported previously by
Bodmeier et al. [56]. Alonso's group later reported the use of these
particles for protein [74, 75], oligonucleotide, and plasmid DNA
delivery [76, 77]. The resulting chitosan/TPP nanoparticles for DNA
delivery were in the range of 100-300 nm depending on the Mw of
the chitosan and showed high physical stability and encapsulation
efficiencies both for plasmid DNA and dsDNA oligomers (20-
mers), independent of chitosan's Mw. The low-Mw chitosan/TPP
nanoparticles gave high gene expression levels in HEK 293 cells
and mediated a strong beta-galactosidase expression in vivo after
intratracheal administration. Chitosan/TPP nanoparticles were also
developed for the delivery of double-stranded small interfering RNA
(siRNA) [78]. In this study, particle size was shown to be aff ected by
chitosan's Mw, concentration, chitosan-to-TPP weight ratio, and pH. In
vitro studies of these particles in two types of cells lines, CHO K1 and
HEK 293, revealed that chitosan/TPP nanoparticles with entrapped
siRNA enhanced gene silencing in comparison with chitosan-siRNA
complexes. This was possibly due to their high binding capacity and
loading efficiency.
As mentioned, the positive charge of chitosan enables the
formation of polyelectrolyte complexes (PEC) with negatively charged
polymers such as negatively charged polysaccharides, nucleic acids,
negatively charged peptides and poly(acrylic acid). Polyelectrolyte
complexation is one of the most frequently used methods to prepare
chitosan nanoparticles. PEC of chitosan with gamma-poly-(glutamic
acid), a natural, non-toxic, and biodegradable negatively charged
polymer have been prepared for oral administration of insulin [63].
These nanoparticles, which were stabilized with TPP and magnesium
sulfate were pH sensitive and had an average size of 218 nm in
diameter. The particles were shown to be safe, adhere to mucosal
surfaces and to induce a significant hypoglycemic action for at least
10 h in diabetic rats when administered orally. The bioavailability of
insulin, which was determined from plasma insulin concentration, was
of 15%. The same group previously reported transdermal delivery of
DNA containing chitosan-gamma-poly-(glutamic acid) nanoparticles