See also Drug Deliver where cationic polymers have been sued. 

Naturally derived Cationic Polymers

Cellulose: (C6H10O5)n  is a polysaccharide consisting of a linear chain of several hundred to many thousands of beta(1-4) linked D-glucose units. Cellulose is a fundamental component of the cell wall of plants, constituting the fundamental raw material in such important processes as papermaking. US2006/0242739). 

Chitson: is a natural cationic copolymer composed of randomly distributed N-acetyl glucosamine and D-glycosamine, varying in composition, sequence and molecular chain lenght. Chitosan is one of the most extensively studies cationic polymers as an antimicrobial agent. It possesses inherent antimicrobial activity against many Gram-positive and Gram negative bacterial and fungi at pH<6. Alhtough the exact emchanisms is not fully understood, several mechanisms have been suggested such as changes which occur in the bacterail membrane permeability, breakdon of the cytoplasmic membrane barrier or the blockage of nutrient transport, resulitng in cell lysis. (Samal, “Cationic polymers and their therapeutic potential, Chem Soc. Rev. (2012)

Cyclodextrins: are sugar derivative pdouced by bacteria grown on starch. 

Dextran: is an FDA approved highly water soluble branch polysaccharide composed of glucose units mianly linked by alpha-1,6-linkages. 

Gelatin: is a natural polymer derived form collagen, commonly applied for pharmaceutical and medical purpsoes because of its biodegradbility and biocompatibility in physiological environments. 

Starch (amylum): is a carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. Starch is the principal storage form of carbohydrates in plans. It is accumulated in large quantities in organs such as seeds (wheat, barley, maize, pea, etc) and tubers (potato and yam ) and is a fundamental constituent of the human diet. As a polymer, starch is often used in paper, cosmetic, pharmaceutical and food industries and also used as a basic component for the manufacture of biodegradable plasstics and environment friendly paints (US 2006/0242739).

Synthetically derived Cationic Polymers

The main difficulties with batch to batch variation or natural polymers can be overcome by synthetic polymers. The bioactive moieties and funcitonal groups can be readily incorporated into the synthetic polyemric system to result in specific MW and block structures with degradable linkages if required. (Samal, “Cationic polymers and their therapeutic potential, Chem Soc. Rev. (2012).

Polyethyleneimine (PEI):  is the most prominent and extensively used cationic polymer containing primary, secondary and tertiary amino functions. It is synthesized in both linerar and branch forms and exists in different MWs. 

Poly(amidoamine)s (PAAs): PAAs are a unique family of synthetic cationic polymers with many desirable properties including biodegradbility, biocompatibility, water solubility and a lower toxicity ompared to other cationic polyerms. PAAs can be obtained by Michael-type polyaddition of primary amines or bis-secondary amines to bis-acrylamides. (Samal, “Cationic polymers and their therapeutic potential, Chem Soc. Rev. (2012)

Poly(amino-co-ester) (PAEs): are a class of synthetic and hydrolytically degradable polyamines originally developed and investigated as cationic polymers for DNA delivery. (Samal, “Cationic polymers and their therapeutic potential, Chem Soc. Rev. (2012)

Poly(2-N,N-dimethylaminoethylmethacrylate (PDMAEMA): is one of the most important pH responsive polymers studies to date. It is water soluble cationic polymer. 

Stimuli-Responsive Cationic Polymers

Advanced therapeutic research demands controlled intelligent systems for various therapeutic applicaitons including controlled delivery, nucleic acid separation and other factors. Cationic polymeric systems with various chemical and structural responsive moieties exhibit the property of responsiveness to external stimuli such as temerpature, pH, ionic concentraiton, light, magnetic field, electric field and chemicals. (Samal, “Cationic polymers and their therapeutic potential, Chem Soc. Rev. (2012)

pH responsive cationic polymers: The presence of ionizable functional groups on a cationic polymer drametically alters its structural properties at, above and below a specific pH called its pKa. This rapid change in the net charge of pendant or backbone groups with respect to pH casues an alteration of the hydrodynamic volume or conformation of the polymer chains. The pH responsive nature of cationic polymers can be used for biomolecule delivery in neutral or alkaline environments. At a pH above the pKa, the pendant amino groups remain non-ionized leaving the polyemric ahin in a collapsed state, while entrapping the biomolecule. As the pH decreases below the amine pKa, the amine groups become protonated and the polyemric cahin expands due to electrostatis repulsion, in this way releasing the entrapped biomolecules into the surroudning medium. Cationic polymers like chitsoan, PEI, PDMAEMA, PAA have basic functional groups such as primary, seconary and tertiary amine groups that beocme ionized as the pH decreases. (Samal, “Cationic polymers and their therapeutic potential, Chem Soc. Rev. (2012)

Temperature (thermal) responsive cationic polymers: change their structural proeprties in response to empterature. Tehy can be acheived by incorproating  or grafting temperature resonsive moeities such as pluronic F-127 or poly(N-isopropyl-acrylamide) (PNIPAM) (Samal, “Cationic polymers and their therapeutic potential, Chem Soc. Rev. (2012)

Multiresponsive cationic polymers: offer responsiveness to two or more external sitmuli. Dual sensitivity was reproted for a novel triblock copolymer consisting of PAA and PEG which was coverted into an injectable pH and termpature sensitive hydrogel. (Samal, “Cationic polymers and their therapeutic potential, Chem Soc. Rev. (2012)