Polymer polycation

Polyplexes. When cationic polymers (polycations) are mixed with the highly negatively charged DNA, they condense into colloids called polyplexes (see Fig. 11. Id). Polyplexes serve as an important nonviral vector for gene delivery, and one polyplex formulation has advanced to the clinical trials.68... 

The polymers used in DDSs may be classified using different criteria. According to the charge they bear, they may be divided into neutral polymers, anionic polymers (polyanions) and cationic polymers (polycations). This chapter is devoted to the DDSs containing cationic polymers of pharmaceutical interest. 

Cationie polymers (polycations, i.e. polyelectrolytes with positive electric charges loeated on the polymeric chain) show remarkable potential in gene delivery as non-viral earners of genetie material as well as in regenerative medieine as matriees eapable of generating new tissues from eells. Indeed,... 

LIQUID CRYSTALLINE POLYMER PolyC i-cyanophenyl i -hexyloxy benzoate methyl slloxane(PCPHS) /CH3... 

Ordered films of magnetite in cellulose can be used as magnetic membranes and assembled multilayers of clay, polymer polycations, and magnetite nanoparticles have been proposed as sensor arrays. ... 

Since multiple electrical and optical functionality must be combined in the fabrication of an OLED, many workers have turned to the techniques of molecular self-assembly in order to optimize the microstructure of the materials used. In turn, such approaches necessitate the incorporation of additional chemical functionality into the molecules. For example, the successive dipping of a substrate into solutions of polyanion and polycation leads to the deposition of poly-ionic bilayers [59, 60]. Since the precursor form of PPV is cationic, this is a very appealing way to tailor its properties. Anionic polymers that have been studied include sulfonatcd polystyrene [59] and sulfonatcd polyanilinc 159, 60]. Thermal conversion of the precursor PPV then results in an electroluminescent blended polymer film. 

The pioneering work on amphiphilic polyelectrolytes goes back to 1951, when Strauss et al. [25] first synthesized amphiphilic polycations by quaternization of poly(2-vinylpyridine) with n-dodecyl bromide. They revealed that the long alkyl side chains attached to partially quaternized poly(vinylpyridine)s tended to aggregate in aqueous solution so that the polymers assumed a compact conformation when the mole fraction of the hydrophobic side chains exceeded a certain critical value. Thus, Strauss et al. became the first to show experimentally the intramolecular micellation of amphiphilic polymers and the existence of a critical content of hydrophobic residues which may be compared to the critical micelle concentration of ordinary surfactants. They called such amphiphilic polyelectrolytes polysoaps [25],... 

Sassoon and Rabani [79] also prepared a two polymer system in which a chromophore was covalently bound to one polyelectrolyte and a donor or acceptor was electrostatically held by the other polyelectrolyte, and showed that its back ET underwent a similar retardation effect. They employed 26 as a photosensitizer, MV2+ as a mediator, and ferricyanide as an acceptor electrostatically bound to the added polycation (polybrene). 

A similar example is the formation of nonstoichiometric interpolymeric complexes between mutually complementary polyelectrolytes — polycation and polyanion [69,70], They behave like true polymer networks and are capable of swelling the interpolymeric complexes between PAAc and polyethylene piperazine swells, for instance, 16-18 times [70], Also advantageous in this case is the possibility to carry out this type of crosslinking in open systems, such as soil. 

As a polycation, chitosan spontaneously forms macromolecular complexes upon reaction with anionic polyelectrolytes. These complexes are generally water-insoluble and form hydrogels [90,91]. A variety of polyelectrolytes can be obtained by changing the chemical structure of component polymers, such as molecular weight, flexibility, fimctional group structure, charge density, hydrophilicity and hydrophobicity, stereoregularity, and compatibility, as... 

Wang, Y. and Dubin, RL., Capillary modification by non-covalent polycation adsorption effects of polymer molecular weight and adsorption ionic strength, Anal. Chem. 71, 3463, 1999. 

Polymeric drugs are macromolecules that elicit biological activity (7). Many synthetic polymers are biologically inert. However, some exhibit toxicity, while others exhibit a wide range of therapeutic activities. There are three kinds of polymer drugs polycations, polyanions, and polynucleotides. 

In 1997, Decher reported a fundamental concept regarding the multilayer nanoassemblies composed of polycations and polyanions [24]. The polymer assemblies were prepared by an alternate adsorption process, as shown in Figure 6.5. If a substrate has an anionic charge on its surface then polycation could adsorb onto the surface as a first layer. Polyanion could subsequently adsorb onto the surface by immersing in a... 

Step 1 Cytotoxicity. Each polymer was evaluated, at least twice, in blind experiments, according to their toxicity toward insulinoma cells. For many polymers alternative suppliers and molecular weights were also tested. In total 37 polyanions were obtained of which 23 were systematically evaluated. By comparison, 29 of the 36 polycations procured were systematically tested. The results of these experiments are provided in Table 4. 

Table 5. Binary screening of polyanions and polycations Polymer... 

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