Chemically Modified Polyelectrolytes
Polyelectrolyte complex (PEC) formation represents a easy however very fascinating precept with significant significance in protein delivery. It's known that conventional polymer-based nanoparticles which might be used for protein delivery are commonly manufactured by way of the use of solvent evaporation, emulsion, dispersion or polymerization of monomers within the inverse section microemulsion [1,2]. The process very often requires using potentially poisonous organic solvents, heat, vigorous agitation or chemicals that might compromise the stability and biocompatibility of the ultimate products [1–3]. Nonetheless, the fabrication process of nano-dimension PEC is simple, and as we speak it represents an attractive different to standard nanoparticulate formulations, which is clear from the recent explosion of literature on the use of PEC in protein delivery [2,4–8].
12.3 Polyelectrolyte complexes
Polyelectrolytes are macromolecular supplies, which have a number of ionizable functional groups having totally different molecular weight and chemical compositions. The charge on the macromolecules is being created due to the partial or complete dissociation of PECs in the aqueous options . In answer, oppositely charged polyelectrolytes are combined concurrently to kind PECs (Fig. 12.2) . Electroneutrality of polyelectrolytes in answer 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 charge .
PECs were first introduced in early 1930s by Bungenberg de Jong and his coresearchers, when they reported formation of colloidal complexes as the advanced coacervates because of the interaction of some naturally occurring polyelectrolytes within the aqueous medium . Nevertheless, insoluble PECs were recognized within the early Nineteen Sixties after the discovery of numerous artificial polymers possessing high cost densities. Alan Michaels and his group had illustrated a number of physicochemical properties of such complexes like swelling behaviors as well as plasticizing traits of the electrolytes . Albrecht Kossel studied the impact of electrostatical forces on the mutual precipitation of varied natural polymers. It was reported that the electrostatic interplay was liable for the part separation of oppositely charged carbohydrate and protein systems . More intensive research on PECs was initiated in 1961, when Michaels and his crew reported about stoichiometric complexes of artificial polyelectrolytes. They had prepared and characterised poly(4-vinylbenzyl-trimethyl ammonium chloride) associated with poly(sodium styrene sulfonate) .
The particles of PECs form by noncovalent electrostatic interactions amongst varied polycations and polyanions . 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 response also influences the degree of ionization, which in turn affects the formation of nanoparticles . 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) . Polyelectrolytes are intriguing class of macromolecules, which comprise dissociated ionic teams [68,70]. These molecules possess macromolecular chains and hold high prices which might be chargeable for their fascinating behaviors. Completely different courses of polyelectrolytes based mostly on their nature are given in Table 12.1. Typically, in preparation of PECs, chemical cross-linkers should not used (besides chemically cross-linked PECs) and hence, these are unhazardous, biocompatible, and well-tolerated . These possess quite a few distinctive characteristics that suit as perfect pharmaceutical excipients to control the drug release kinetics.
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