Other Natural Cationic Polymers

Although chitosan is the most important and well-studied natural cationic polymer, other natural cationic polymers have also been investigated for their applieations in gene and drug delivery. Different from ehitosan, these polymers are eationic modified natural polymers or cationic peptides, sueh as eationie eellulose, cationie dextrin or starch, cationic gelation, and others. 

Cellulose, the most abundant polysaecharide in nature, is a non-ionic polymer with strong intermolecular hydrogen bonds. The eationie 

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In the area of municipal and iadustrial wastewater treatment, the principal environmental issue is the toxicity of residual flocculating agents ia the effluent. Laboratory studies have shown that cationic polymers are toxic to fish because of the iateraction of these polymers with giU. membranes. Nonionic and anionic polymers show no toxicity (82,83). Other studies have shown that ia natural systems the suspended inorganic matter and humic substances substantially reduce the toxicity of added cationic polymer, and the polymers have been used successfully ia fish hatcheries (84—86). Based on these results, the EPA has added a protocol for testing these polymers for toxicity toward fish ia the presence of humic acids (87). The addition of anionic polymers to effluent streams containing cationic polymers to reduce their toxicity has been mentioned ia the patent Hterature (83). 

One of the prime environmental objectives is the removal of suspended contaminants from water and waste streams. Water turbidity in nature is the result of colloidal clay dispersion and the color is from decayed wood and leaves (tannins and lignins) and organic soil matter. In addition to these contaminants, there are viruses, algae, bacteria, metal oxides, oils and other pollutants. In recent years, synthetic organic polyelectrolyes, in particular the cationic polymers, have been used very effectively in water treatment (3). These polyelectrolytes are high... 

Polysaccharide Containing Polymers. Chitosan (Table 7.3-1) is composed of 2-amino-2-deoxy p-D-glucan and is prepared from naturally occurring chitin via alkaline deacetylation. Unlike other cationic polymers chitosan is nontoxic and biodegradable, making it an ideal candidate for therapeutic applications. Although the density of positive charges of chitosan is lower than for other cationic polymers. 

Cationic nanocarriers are prepared from natural or synthetic polymers. The most widely used cationic polymers have been reported as PEI, PLL, poly-methacrylates (PMA), chitosan and cationic modifications of other polymers such as cyclodextrin, gelatin and imidazole-containing polymers. ... 

Cationic lipids and cationic polymers are designed as gene delivery systems on the nanoscale. Especially chitosan is under focus as a biodegradable, natural biopolymer, used both as the polyplex and also as a coating material for other polyplexes. Chitosan-coated poly(isohexyl cyanoacrylate) nanoparticles have also been developed for intravenous delivery of siRNA and no evidence of toxicity was observed after intravenous administration for 30... 

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