Polyelectrolyte advanced (PEC) formation represents a simple but very fascinating precept with significant significance in protein delivery. It’s known that standard polymer-primarily based nanoparticles which are used for protein delivery are commonly manufactured via using solvent evaporation, emulsion, dispersion or polymerization of monomers in the inverse phase microemulsion [1,2]. The process fairly often requires the use of probably toxic organic solvents, heat, vigorous agitation or chemicals which may compromise the stability and biocompatibility of the final products [1–3]. However, the fabrication process of nano-size PEC is simple, and at the moment it represents an attractive different to conventional nanoparticulate formulations, which is evident from the recent explosion of literature on using PEC in protein delivery [2,four–8].

12.3 Polyelectrolyte complexes

Polyelectrolytes are macromolecular supplies, which have multiple ionizable functional groups having totally different molecular weight and chemical compositions. The charge on the macromolecules is being created because of the partial or full dissociation of PECs in the aqueous options [61]. In resolution, oppositely charged polyelectrolytes are blended simultaneously to kind PECs (Fig. 12.2) [62]. Electroneutrality of polyelectrolytes in answer is maintained by the neutralization of charge for a repeating unit by oppositely charge. The repeating units, for example, positive charged electrolytes are accompanied by the smaller ions of negative cost [63].

PECs had been first introduced in early Thirties by Bungenberg de Jong and his coresearchers, after they reported formation of colloidal complexes as the complex coacervates as a result of interplay of some naturally occurring polyelectrolytes within the aqueous medium [64]. Nonetheless, insoluble PECs have been recognized in the early Nineteen Sixties after the discovery of numerous artificial polymers possessing high cost densities. Alan Michaels and his group had illustrated several physicochemical properties of such complexes like swelling behaviors as well as plasticizing characteristics of the electrolytes [65]. Albrecht Kossel studied the impact of electrostatical forces on the mutual precipitation of assorted natural polymers. It was reported that the electrostatic interaction was accountable for the phase separation of oppositely charged carbohydrate and protein systems [66]. More intensive research on PECs was initiated in 1961, when Michaels and his group reported about stoichiometric complexes of artificial polyelectrolytes. They had prepared and characterized poly(four-vinylbenzyl-trimethyl ammonium chloride) associated with poly(sodium styrene sulfonate) [67].

The particles of PECs type by noncovalent electrostatic interactions amongst varied polycations and polyanions [68]. Upon the blending of oppositely charged polyelectrolytes in the aqueous resolution medium under the managed conditions of ionic strength, pH, focus of polyelectrolytes, ionic group distribution, molecular weight of polymers, and mixing ratio, a dense phase separates out from the solvent [62,68]. Additionally, the order of polyelectrolytic reaction additionally influences the degree of ionization, which in flip impacts 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 include dissociated ionic groups [68,70]. These molecules possess macromolecular chains and hold high fees which might be chargeable for their fascinating behaviors. Completely different courses of polyelectrolytes primarily based on their nature are given in Table 12.1. Generally, in preparation of PECs, chemical cross-linkers usually are not used (except chemically cross-linked PECs) and therefore, these are unhazardous, biocompatible, and well-tolerated [68]. These possess numerous unique traits that suit as excellent pharmaceutical excipients to control the drug launch kinetics.

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