Polyelectrolyte advanced (PEC) formation represents a simple however very attention-grabbing precept with significant importance in protein delivery. It’s known that standard polymer-primarily based nanoparticles that are used for protein delivery are commonly manufactured via the usage of solvent evaporation, emulsion, dispersion or polymerization of monomers in the inverse section microemulsion [1,2]. The process fairly often requires the usage of probably poisonous organic solvents, heat, vigorous agitation or chemical compounds which may compromise the stability and biocompatibility of the ultimate products [1–3]. Nevertheless, the fabrication process of nano-dimension PEC is simple, and in the present day it represents an attractive various to traditional nanoparticulate formulations, which is evident from the latest explosion of literature on the usage of PEC in protein delivery [2,four–8].

12.three Polyelectrolyte complexes

Polyelectrolytes are macromolecular materials, which have multiple ionizable functional teams having different molecular weight and chemical compositions. The charge on the macromolecules is being created as a result of partial or complete dissociation of PECs in the aqueous solutions [61]. In resolution, oppositely charged polyelectrolytes are combined concurrently to form PECs (Fig. 12.2) [62]. Electroneutrality of polyelectrolytes in resolution is maintained by the neutralization of charge for a repeating unit by oppositely charge. The repeating units, for instance, positive charged electrolytes are accompanied by the smaller ions of negative cost [63].

PECs were first launched in early Nineteen Thirties by Bungenberg de Jong and his coresearchers, once they reported formation of colloidal complexes as the advanced coacervates due to the interplay of some naturally occurring polyelectrolytes within the aqueous medium [64]. Nonetheless, insoluble PECs had been recognized in the early 1960s after the discovery of quite a few synthetic polymers possessing high charge densities. Alan Michaels and his group had illustrated a number of physicochemical properties of such complexes like swelling behaviors as well as plasticizing characteristics of the electrolytes [65]. Albrecht Kossel studied the effect of electrostatical forces on the mutual precipitation of various natural polymers. It was reported that the electrostatic interaction was answerable for the section separation of oppositely charged carbohydrate and protein systems [66]. More intensive research on PECs was initiated in 1961, when Michaels and his team reported about stoichiometric complexes of artificial polyelectrolytes. They had prepared and characterised poly(4-vinylbenzyl-trimethyl ammonium chloride) associated with poly(sodium styrene sulfonate) [67].

The particles of PECs kind by noncovalent electrostatic interactions amongst various polycations and polyanions [68]. Upon the mixing of oppositely charged polyelectrolytes within the aqueous solution medium under the controlled conditions of ionic energy, pH, focus of polyelectrolytes, ionic group distribution, molecular weight of polymers, and mixing ratio, a dense section separates out from the solvent [62,68]. Additionally, the order of polyelectrolytic reaction also influences the degree of ionization, which in turn affects the formation of nanoparticles [69]. Polyelectrolyte complexation takes place between oppositely charged species and are named accordingly (e.g., polyelectrolyte–surfactant complexes, polyelectrolyte–nucleic acid complexes, PECs, polyelectrolyte–drug complexes) [70]. Polyelectrolytes are intriguing class of macromolecules, which contain dissociated ionic teams [68,70]. These molecules possess macromolecular chains and hold high charges that are answerable for their fascinating behaviors. Different lessons of polyelectrolytes primarily based on their nature are given in Table 12.1. Typically, in preparation of PECs, chemical cross-linkers will not be used (except chemically cross-linked PECs) and hence, those are unhazardous, biocompatible, and well-tolerated [68]. These possess quite a few unique characteristics that suit as very best pharmaceutical excipients to manage the drug release kinetics.

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