Chitosan Transfection mechanism

The transfection mechanism of plasmid-chitosan complexes as well as the relationship between transfection activity and cell uptake was analyzed by using fluorescein isothiocyanate-labeled plasmid and Texas-Red-labeled chitosan. Several factors affect transfection activity and cell uptake, for example the molecular mass of chitosan, stoichiometry of complex, seriun concentration and the pH of the transfection medium. The level of transfection with plasmid-chitosan complexes was found to be highest when the molecular mass of chitosan was 40 or 84 kDa, the ratio of chitosan nitrogen to DNA phosphate was 5, and serum at pH 7.0 was 10%. Plasmid-chitosan complexes most likely condense to form large aggregates (5-8 p,m), which absorb to the cell surface. After this, plasmid-chitosan complexes are endocytosed, and accumulate in the nucleus [97]. 

Ishii et al. [64] explained the transfection mechanism of chitosan/DNA complexes in relation to cell uptake. They used fluorescein isothiocyanate-labeled plasmid DNA and Texas Red-labeled chitosan. They found that the transfection of chitosan/DNA complexes was higher with the molecular weight of chitosan at 40 or 84 kDa and N/P ratio at 5 (Figure 20.4). The transfection... 

DNA molecules (polyplexes). Although there are a lot of reports on chitosan-based DNA nanocarriers varying in sizes (20-250 nm and higher), studies regarding effects and the chitosan-specific transfection mechanisms remain insufficient. It is shown that the level of transfection depends upon several factors, for instance chitosan molecular weight (from 22 kDa [65] to 400 kDa [66]), the ratio of chitosan nitrogen to DNA phosphate (N/P ratio), as well as serum concentration and pH of transfection medium, and finally on cell line [67],... 

Ishii T, Okahata Y, Sato T. Mechanism of cell transfection with plasmid/chitosan complexes. Biochim Biophys Acta 2001, 1514, 51-64. 

Ishii, T., Okahata, Y., and Sato, T. 2001. Mechanism of ceU transfection with plasmid/chitosan complexes. Biochimica et Biophysica Acta 15 51-64. 

Among the used cells, HEK293 cells were more efficiently transfected than other cells with chitosan/DNA complexes (Leong et al. 1998), although its exact mechanism is not clear. 

Transferrin as a ligand efficiently transfers small MW drugs, liposomes, and macromolecules through a receptor-mediated endocytosis mechanism (Deshpande et al. 1994) because the transform receptors are found on many mammalian cells (Dautry-Varsat 1986). Mao et al. (2001) coupled transferrin with chitosan nanoparticles prepared by chitosan and sodium sulfate. The transferrin-conjugated chitosan nanoparticles showed a fourfold increase of transfection efficiency in HEK293 cells and HeLa cells as compared with the chitosan ones. 

Although the mechanism is not clear, chitosan- or chitosan-derivative-mediated transfection depends on the cell type. Among cells used, HEK293 cells are the most efficiently transfected [24]. 

Kim et al. prepared maimosylated chitosan (MC) to obtain receptor-mediated endocytosis for targeting to APCs [39]. The results indicated that MC/DNA complexes showed higher transfection efficiency compared with WSC/DNA complexes in Raw 264.7 cells, owing to the receptor-mediated endocytosis mechanism [39]. They also performed interleukin 12 (lL-12) gene delivery through intratumoral injection of MC/IL-12 complexes into B ALB/C mice bearing tumors at the injected sites [40]. Intratumoral delivery of MC/EL-12 complexes suppressed more tumor growth than the control due to the mechanism of apoptosis and cell cycle arrest. 

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