Bioactivities of Chitosan and Its Derivatives - Chitosan Based Hydrogels: Functions and Applications - page 114

results indicated that γ-PGA plays multiple important roles in enhancing the cellular
uptake and transfection efficiency of CS/DNA/γ-PGA nanoparticles. This high transfec-
tion efficiency of the nonviral gene delivery system could be attributed to the synergic
effect of ultra-low molecular weight chitosan (ULMWCh) and the low charge density of
the sodium hyaluronate (HA) chain for easy release of DNA, which makes the system
suitable for targeted gene delivery [50].
Chitosan/trimeric sodium phosphate (TPP) nanoparticles showed high encapsulation
efficiencies for both plasmid DNA and dsDNA oligomers (20-mers), independent of chito-
san MW. LMW chitosan (LMWC)/TPP nanoparticles gave high gene expression levels in
HEK293 cells already 2 days after transfection, reaching a plateau of sustained and high
gene expression between 4 and 10 days. The inclusion of BSA into the nanostructures did
not alter the inherent transfection efficiency of nanoparticles. Confocal studies suggest
endocytotic cellular uptake of the nanoparticles and subsequent release into the cytoplasm
within 14 h. LMWC/TPP nanoparticles mediated a strong β-galactosidaseexpression
in vivo after intratracheal administration. That is to say, ionically cross-linked chitosan/
TPP nanoparticles serve as a biocompatible nonviral gene delivery system and generate a
solid ground for further optimization studies, for example with regard to steric stabiliza-
tion and targeting [51].
3.1.1.4 Clinical Applications of Chitosan-DNA Systems
To test the chitosan-DNA system as a potential DNA vaccine candidate, Kumar et al. [52]
utilized a strategy involving an intranasal gene transfer, referred to as IGT, complexed
with chitosan-DNA nanospheres containing a cocktail of DNA encoding nine immuno-
genic respiratory syncytial virus (RSV) antigens. This system was tested against acute RSV
infection in a BALB/c mouse model. The effectiveness and mechanism of this IGT strategy
were investigated, and the results demonstrated that IGT was safe and effective against
RSV and significantly attenuates the pulmonary inflammation induced by RSV infection.
A single dose of about 1 mg/kg body weight was capable of decreasing viral titers by two
orders of magnitude (100-fold) on primary infection. This therapy works by induction of
high levels of both serum IgG and mucosal IgA antibodies, generation of effective control
response, and elevated lung-specific production of interferon-γ (IFN-γ)-antiviral action.
Also, IGT significantly decreased pulmonary inflammation and did not alter airway
hyperresponsiveness, making it safe for in vivo use.
Another application of chitosan-DNA gene therapy is against Coxsackie virus B3 infec-
tions, which cause acute and chronic myocarditis [53]. Intranasal delivery of the chitosan-
DNA complex prepared by vortexing DNA with chitosan resulted in transgenic DNA
expression in mouse nasopharynx and also induced mucosal SIgA secretion. Sun et al. [54]
constructed a eukaryotic expression vector pVAX1-pZP3a as an oral zona pellucida (ZP)
DNA contraceptive and successfully encapsulated in nanoparticles with chitosan to target
ZP, the extracellular matrix surrounding oocytes. After 5 days of feeding to mice, the tran-
scription and expression of pZP3 were found in mouse alvine chorion. Okamoto et al. [55]
investigated the potential of chitosan in the form of inhaled powder for gene delivery pur-
poses by preparing powders using pCMV-Luc as a reporter gene and LMWC (3-30 kDa) as
a cationic vector with supercritical CO 2 . This powder was administered to the lungs of
mice and their transfection efficiency was compared to that of DNA solution and DNA
powder without the cationic vector. The gene powder with the cationic vector was found
to be an excellent gene delivery system to the lungs.