Polyelectrolyte complexes protein carriers

Apart from specific interactions between a target protein and a ligand-polymer conjugate, nonspecific interactions of protein impurities with the polymer backbone could take place. The nonspecific interactions limit the efficiency of the affinity precipitation technique, and significant efforts were made to reduce these interactions. The advantage of polyelectrolyte complexes as carriers for affinity precipitation is low nonspecific coprecipitation of proteins when the polymer undergoes a soluble-insoluble transition (10). 

Cationic polymers are of particular interest carriers in drug and gene deliveiy because of their ability to promote cellular uptake.This holds also for the delivery of proteins, especially for those that possess an overall anionic charge at pH values above the isoelectric point (p/). These proteins can form soluble, nanosized, polyelectrolyte complexes with natural or synthetic cationic polymers by simply mixing the oppositely charged protein and polymer that self-assemble by electrostatic attraction, as represented in Scheme 14.1. 

Hu Y, Yang T, Hu X (2012) Novel polysaccharides-based nanoparticle carriers prepared by polyelectrolyte complexation for protein drug delivery. Polym Bull 68 1183-1199... 

The existence of soluble protein-polyelectrolyte complexes makes polyelectrolytes potentially important enzyme carriers, in which the enzyme activity could be controlled. For example, the tryptic digestion of hemoglobin with PAA as a carrier was studied by Morawetz [56] in 1955. The trypsin activity was varied by adjusting pH and polymer concentration. It was found that the carrier could even activate the enzyme at low pH, as shown by Fig. 15.22. As shown in Fig. 15.23, the complex of trypsin with KPVS was found to retain activity in a wide pH range by Kokufuta [57]. Based on the study of trypsin-carboxymethyl-cellulose complexes, Larionova et al. [58] concluded that some protein-polyelectrolyte complexes can provide extra thermal stability at the preservation of high biological activity. 

The interaction between oppositely charged polyelectrolytes in aqueous environment leads to the formation of PECs. These PECs meet the profile of requirements of biocompatible polymer systems and can be adapted to meet the various requirements like carrier substances and components for active substances. The initial studies on macromolecular complexes were reported by Kossel. He described the formation of nucleoprotein complex due to interaction of proteins with nucleic acid and form heavy precipitates when mixed even at very high dilutions. In 1949, Fuoss and Sadek °... 

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