Several approaches have been employed for directing the intracellular trafficking
of DNA to the nucleus. Cationic polymers have been used to condense and
deliver DNA and a few specific examples using chitosan as cationic polymer
have been described. The concerted efforts in gene therapy to date have
provided fruitful achievements toward a new era of curing human diseases. A
number of obstacles, however, still must be surmounted for successful clinical
applications.
Therefore, chitosan-plasmid and quaternised chitosan-plasmid complexes
(polyplexes) were investigated for their ability to transfect COS-1 cells and the
results were compared with Transfectam/DNA lipoplexes for transfection
efficiency. All of the chitoplexes utilised in this study proved to transfect COS-1
cells, however to a lesser extent than the Transfectam/DNA lipoplexes, which
served as a positive control. Complexes formed with quaternised trimethyl and
triethyl chitosan oligomers, specifically TMO L and TEO L, proved to be superior
transfecting agents compared to other chitosans. The molecular mass of
chitosan is considered to influence the stability of the chitosan/DNA polyplex, the
efficiency of cell uptake and the dissociation of DNA from the complex after
endocytosis.
In literature it was shown that the toxicity of the chitosan1DNA polyplexes is
relatively low compared to viral gene and lipid non-viral delivery vectors. This
study showed that the percentage viable COS-1 cells when transfected with the
chitosan polymers, oligomers, quaternised chitosan polymers and quaternised
chitosan oligomers (chitoplexes) was higher than the percentage viable cells
when transfected with lipoplexes prepared with Transfectam with the MTT
assay. The Transfectam/DNA lipoplexes induced cell damage and a decreased
viability of COS-1 cells were found. Chitosan/DNA and quaternised
chitosan/DNA complexes did not affect the viability of the cell line. The degree of
quaternisation of the polymers and oligomers and molecular size proved to be
two important factors when considering effective non-viral gene delivery.
It can be concluded that chitosan, especially quaternised oligomeric derivatives
are polysaccharides that demonstrate much potential as a gene delivery system.
The high solubility and low toxicity of chitosan allow its use in a wide variety of
applications in the pharmaceutical industry and, as shown in this study, in gene
delivery. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2006.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/1015 |
| Date | January 2005 |
| Creators | Venter, Chrizelle |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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