Polyelectrolyte advanced (PEC) formation represents a easy but very interesting precept with significant importance in protein delivery. It is known that conventional polymer-based nanoparticles which can be used for protein delivery are commonly manufactured by way of the usage of solvent evaporation, emulsion, dispersion or polymerization of monomers within the inverse section microemulsion [1,2]. The process very often requires the usage of probably poisonous organic solvents, heat, vigorous agitation or chemicals that might compromise the stability and biocompatibility of the ultimate products [1–3]. However, the fabrication process of nano-dimension PEC is easy, and today it represents an attractive various to traditional nanoparticulate formulations, which is obvious from the latest explosion of literature on the use of PEC in protein delivery [2,four–8].
12.3 Polyelectrolyte complexes
Polyelectrolytes are macromolecular materials, which have a number of ionizable functional groups having totally different molecular weight and chemical compositions. The cost on the macromolecules is being created due to the partial or full dissociation of PECs in the aqueous options [61]. In resolution, oppositely charged polyelectrolytes are mixed concurrently to form PECs (Fig. 12.2) [62]. Electroneutrality of polyelectrolytes in resolution is maintained by the neutralization of cost 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 introduced in early Thirties by Bungenberg de Jong and his coresearchers, once they reported formation of colloidal complexes because the complicated coacervates due to the interplay of some naturally occurring polyelectrolytes in the aqueous medium [64]. Nevertheless, insoluble PECs were recognized in the early 1960s after the discovery of numerous synthetic polymers possessing high charge densities. Alan Michaels and his staff had illustrated several physicochemical properties of such complexes like swelling behaviors as well as plasticizing traits of the electrolytes [65]. Albrecht Kossel studied the impact of electrostatical forces on the mutual precipitation of varied natural polymers. It was reported that the electrostatic interplay was chargeable for the section separation of oppositely charged carbohydrate and protein systems [66]. More extensive research on PECs was initiated in 1961, when Michaels and his staff 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 numerous polycations and polyanions [68]. Upon the blending of oppositely charged polyelectrolytes in the aqueous solution medium under the managed conditions of ionic energy, pH, focus of polyelectrolytes, ionic group distribution, molecular weight of polymers, and mixing ratio, a dense part separates out from the solvent [62,68]. Additionally, the order of polyelectrolytic response also influences the degree of ionization, which in turn 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 teams [68,70]. These molecules possess macromolecular chains and hold high charges which might be accountable for their fascinating behaviors. Totally different lessons of polyelectrolytes based on their nature are given in Table 12.1. Usually, in preparation of PECs, chemical cross-linkers will not be used (except chemically cross-linked PECs) and hence, these are nontoxic, biocompatible, and well-tolerated [68]. These possess numerous distinctive traits that suit as splendid pharmaceutical excipients to regulate the drug release kinetics.
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