Biomedical Engineering Reference
In-Depth Information
(Scheme 4.5B).
54
These compounds exhibited good ability to condense plasmid
DNA and siRNA, much lower cytotoxicity, and higher transfection efficiency
than 25 kDa PEI in HEK293, L929, and COS7 cell lines.
4.3.2 Cell-Targeted Chitosans
Inefficient release of the polymer/DNA complexes from endocytic vesicles into
the cytoplasm is one of the primary causes of poor gene delivery. Therefore,
various specific ligands, such as galactose, transferrin, folate, RGD, mannose,
etc., have been incorporated into chitosan to enhance the cell-specific delivery.
Lu et al. synthesized lactobionic acid-modified N-succinyl-chitosan-g-PEI
copolymers as gene vectors with hepatocyte targeting properties.
55
These
compounds showed higher gene transfection efficiency and cell specificity
compared to 25 kDa PEI in HepG2 cells, which therefore has the potential
to be a safe and efficient gene vector. Recently, Mohammadi et al. pre-
pared chitosan-DNA nanoparticles by a complex coacervation process.
56
Fibronectin attachment protein of Mycobacterium bovis (FAP-B) was added to
the chitosan-DNA nanoparticles via electrostatic attraction as a ligand for
attachment to its specific receptors on the surface of epithelial cells. This
compound showed 10-fold higher transfection efficiency than a nonspecific
chitosan control in alveolar epithelial cells (A549), and higher cell viability
compared to Turbofect control. Han et al. developed a cyclic RGD peptide-
labeled chitosan nanoparticle by a thiolation reaction for tumor-targeted
delivery of siRNA.
57
The cyclic RGD provided conformation stability and
improved binding selectivity for the a
v
b
3
integrin overexpressed tumor cells.
They found that this targeted delivery system-mediated gene silencing
significantly enhanced antitumor therapeutic efficacy compared with a
nontargeted delivery system in preclinical ovarian cancer models. Du et al.
synthesized folic acid-conjugated stearic acid-grafted chitosan micelles by a 1-
ethyl-3-(3-dimethylaminopropyl)carbodiimide coupling reaction for specific
receptor-mediated gene delivery.
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They found that folate conjugation
increased the intracellular uptake of complexes in folate receptor-positive
SKOV3 cells via folate receptor-mediated endocytosis, and resulted in higher
transfection efficiency.
d
n
4
y
3
n
g
|
3
4.3.3 Other Chitosan Derivatives
Most of the modifications mentioned above were made via an amidation
reaction, which could consume the amino group of chitosans and influence the
cationic property of chitosan-mediated gene delivery, even resulting in higher
cytotoxity. As a recent alternative, thiolated chitosan has been designed
and used as a gene vector. The free thiol groups on its side chains can
form disulfide bonds with mucin glycoproteins on cell membranes, thereby
promoting
cellular
uptake
of
the
thiolated
chitosan/pDNA
complexes
(Scheme 4.6A).
59
Li et al. designed a glutathione- and PMPEG-modified
