Natural cationic polymers

Natural polymers are generally known for their biocompatibility, biodegradability and non-toxic properties. Usually they are obtained from renewable resources because of their abundance in nature. On the other hand, they have some disadvantages. Natural polymers may cause immunogenic responses in biological systems. Moreover, long purification steps are required in order to reduce or prevent batch-to-batch variation.  

One of the most important properties of chitosan is its antitumor activities for cancer therapy. Chitosan is reported to cause apoptosis and cancer cell cytotoxicity through caspase-3 activation. This property has been demonstrated on different tumor cells such as bladder, breast and colon cancer cells in different studies. Chitosan also has immunoadjuvant effects. It has been shown to stimulate macrophages and polymorphonuclear cells, thus inhibiting tumor cell proliferation. Thanks to these properties, chitosan has been extensively studied as a polymer for nanocarriers for decades. 

In the literature, chitosan nanoparticles have been shown to neutralize the surface charge of liver cancer eells, deerease the membrane potential of mitochondria and indicate lipid peroxidation thus they eause neerotic death. Chitosan nanoparticles form either polyplexes or eneapsulate aetive molecules in their nanoparticle matrix.However, chitosan nanoparticles have lower transfection efficiency than synthetic cationic polymers sueh as polyethylenimine because of their lower endosomal escape.  

Dextran can be modified easily and cationic derivatives are obtained by reaction with diethylaminoethyl (DEAE) reagents or spermine. DEAE-dextran is one of the pioneer cationic polymers for gene delivery. However, PLL and other synthetic polymers have replaced dextran these days because of low transfection efficiency and toxicity problems of DEAE-dextran. Spermine-dextran (MW 9000-11 000 g mol ) is used as an siRNA delivery agent to cancer cells, with low toxicity and high loading capacity on HeLa-Zwc cells, and was proved to be a safe and effective acid-sensitive carrier for gene delivery by Cohen et al. Researchers showed that cationic dextran derivatives (MW 70 kDa) have also reverse tumor-associated macrophage (TAM) polarization, promote IL-12 expression in tumor TAMs and thereby enhance the tumoricidal capacity of TAMs.  

Cationic derivatives of collagen and gelatin are studied for delivery of anionic molecules such as drugs, genes and other therapeutics. 

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Natural cationic polymers are generally non-toxic, derived from renewable resources, biocompatible, biodegradable and possess low immunogenicity. Most natural cationic polymers contain reactive sites, which can be easily modified to improve physicochemical properties. 

Natural cationic polymers are derived from renewable sources and possess inherent positive charges. They are biodegradable and often possess low immunogenicity and low toxicity. Numerous natural cationic polymers have functional groups like carboxylic acid groups that can be further modified to carry therapeutic molecules. 

A list of natural cationic polymers enabling in vivoHn vitro gene therapy to the brain is provided in Table 17.3. 

Natural Cationic Polymers for Advanced Gene and Drug Delivery... 

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. 

An alternate and improved means to achieve enhanced coagulation in treating drinking water, a composition for removing turbidity, particles, and color from drinking water, includes (a) primary polymeric coagulant refers to a cationic polymer (a natural, cationic polymer as chitosan or a cationic starch) which enhances the... 

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