Cationic polymer adsorption

The Jordi polyethyleneimine phase has been developed in an attempt to block adsorptive effects of the PDVB surfaces toward cationic polymers such as chitosan and quaternary water-soluble flocculants (Fig. 13.17). 

Plasmid DNA can be complexed electrostatically with cationic polymers. These complexes can be used for gene transfer [241]. Like the complexes of DNA with cationic lipids these complexes adhere to the cell surface with their cationic surface charges. Thereafter, they are internalized, presumably by adsorptive endocytosis. 

Cationic polyacrylamide may be used in the initial treatment stages to promote rapid polymer adsorption (201). Adjustment of the pH may allow deeper penetration of the fluids in an aluminate crosslinking system prior to gelation (202). A process involving injection of alternate slugs of stoichiometrically equivalent amounts of partially hydrolyzed polyacrylamide and Al O ) has been evaluated in the laboratory permeability of sana packs were reduced by more than 96% (203). Mixtures of Al(IIl) and Zr(IV) have also been evaluated as partially hydrolyzed polyacrylamide crosslinkers (204). 

If only electrostatic effects are responsible for polymer adsorption and flocculation, our results can be explained according to the same scheme as that used by Furusawa et Al.(20) to interprete the destabilization of negatively charged latex by a cationic polymer. In a first step, the adsorption of the polymer leads to the neutralization of the particles which are no more stabilized by electrostatic repulsions and there is flocculation (we have not studied this step since in our experiments polymer was always in large excess with respect to Al(0H)3). In a second step the adsorption inverses the charge and (we have indeed measured by... 

The retention of cationic polymers by cellulose is most readily explained by ionic interaction between the cationic group of the polymer and the acidic groups of cellulose, but there is also evidence that hydrogen bonding participates to a lesser extent in the adsorption process. 

Destabilisation of the alumina at pH 5 where the particles are positively charged shows quite similar trends, the principal difference being that the cationic polymer is completely ineffective. Presumably, the positive charges on both particles and polymer are sufficient to prevent adsorption of the relatively small, highly charged polyions. The behaviour of the non-ionic and anionic polymers is essentially the same as at pH 11. Destabilisation by the addition of... 

Hexacyanoferrates were immobilized on Au covered with SAM of 3,3 -thiodipropionic acid [86]. It has been found from voltammetric studies that the surface coverage of hexacyanoferrate is close to one monolayer and such an electrode exhibits very good surface redox behavior. Cheng et al. [87] have described the formation of an extremely thin multilayer film of polybasic lanthanide heteropolytungstate-molybdate complex and cationic polymer of quaternary poly(4-vinylpyridine), partially complexed with osmium bis(2,2 -bipyridine) on a gold electrode precoated with a cysteamine SAM. Consequently, adsorption of inorganic species might also be related to the properties of SAMs. This problem will be discussed in detail in a separate section later. 

Cationic polymer is also frequently examined to increase the potential of a gene drug. Large molecular weight cationic polymers can condense pDNA more efficiently than cationic liposomes. They include poly-L-lysine (PLL), poly-L-omithine, polyethyleneimine (PEI), chitosan, starburst dendrimer and various novel synthetic polymers. These polymers can enhance the cellular uptake of pDNA by nonspecific adsorptive endocytosis. 

FSCE separation of a negatively charged bovine anhydrase II ladder was achieved in an oxidized PDMS channel, where the negative charge of the oxidized surface minimized protein adsorption through coulombic repulsion. Separation of positively charged proteins was also achieved after the attachment of a cationic polymer to the PDMS surface [1033]. 

Stock composition, kinetics of adsorption and hydrodynamic shear dictate the point at which a cationic polymer is added to a papermaking furnish in order to induce flocculation. Flocculation of cellulose fibers in turbulent flow proceeds very rapidly and is completed in less than two seconds.120-123 Flocks form due to charge interactions through a patch-type or a bridging-type mechanism. However, these flocks will be sensitive to shear force and deflocculation and reflocculation might occur. 

Mahanta D. and Rahman, A., Control of wet-end chemistry by synthetic organic polymers Adsorption of cationic PAA onto cellulose pulp, Indian J. Chem. A, 25A, 825, 1986. 

The choice of eluent system depends on the polymer type. For most non-ionic hydrophilic polymers, water can be used. However much more complex eluent systems are needed, for anionic and cationic polymers where interactions with the column based on ion exclusion, inclusion and exchange, adsorption by hydrogen bonding or hydrophobic interactions and intramolecular electrostatic effects, are possible. This can often make method development in aqueous SEC extremely difficult and time-consuming. 

For the removal of EPS from final solutions of bioproducts, selective adsorption has proven to be the most effective technique. Therefore considerable effort is being put into the development of adsorbents capable of retaining high EPS selectivity under physiological conditions (ionic strength of fi=Q.Q5-Q.2, neutral pH). Recently, numerous cationic polymer adsorbents have been developed for removing EPS from protein solutions. This article will elucidate the chromatographic properties... 

Another approach to reducing the EOF as well as wall adsorption is to add a compound to the running buffer that will compete with the solute for the silanol sites on the surface. These materials must have some affinity for the charged or polar sites on the inner wall and so they must, themselves, be hydrophilic or charged. Nonionic surfactants are hydrophilic to prevent solute adsorption on the wall and block the silanols in order to reduce the EOF. The use of cationic polymers in the buffer results in a reversal of EOF to the anodic direc-... 

Another approach is to use polycation complexes, which can be electrostatically attracted and adsorbed to the negatively charged cell membranes and lead to electrostatically adsorptive endocytosis [155, 156], Eor example, cationized polymer conjugates [157], proteins [158, 159], and nanoparticles [96, 160, 161] exhibit enhanced cellular intemahzations when compared with their noncationized counterparts. Cationic charges, however, can cause severe serum inhibition and rapid clearance from the plasma compartment [162-164] for instance, a cationized antibody had a 58-fold increase in the systemic clearance from the plasma compartment... 

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